tag:blogger.com,1999:blog-13842191107194594342024-02-19T17:52:44.627+02:00DepotBassam.coma place for ideas, electronics, prototyping, DIY technology, knowledge and arts. However, I don't want to promise anything, maybe this blog will have its own life and it will grow and develop the way it sees fit.Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.comBlogger12125tag:blogger.com,1999:blog-1384219110719459434.post-85078369468322448022015-01-07T20:20:00.000+02:002015-01-07T20:20:32.972+02:00Kickstarter 2014 - Pledges from the Arab world<a href="https://www.kickstarter.com/" target="_blank">Kickstarter </a>released their numbers for 2014.While these numbers are amazing to look at and wonder about the worldwide impact of crowdfunding, I was interested in collecting some data related to the Arab world.<br />
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Here's a table showing the number of backers and the pledged dollar amount for the top Arab backer countries:<br />
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UAE is at the lead, followed by Oman in terms of number of backers, and Saudi Arabia in terms of pledged USD.<br />
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Only lately Kickstarter started allowing projects from a select few countries outside the US to run on its platform. Luckily <a href="https://www.zoomaal.com/" target="_blank">Zoomal </a>has been doing a great job as the leading crowdfunding platform in the Arab world, it would be interesting to see and compare how much money has been raised vs. spent in the Arab world on crowdfunded projects.<br />
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source: <a href="https://www.kickstarter.com/year/2014/">https://www.kickstarter.com/year/2014/data</a><br />
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<br />Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com1tag:blogger.com,1999:blog-1384219110719459434.post-64889309538153310152012-06-26T23:45:00.000+03:002012-06-26T23:56:32.520+03:00Making Beirut v1.0<div class="separator" style="clear: both; text-align: center;">
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I was always frustrated of how the hardware and the DIY community is still small in Lebanon. This keeps reminding me of how we are brought up into thinking that we are not made for it. It is just not meant to be: we are too busy with our social, political and economic problems that for some reason we forgot a big problem- we just don't make stuff anymore we consume. <br />
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Obviously the community is there, it just need the right environment to grow. "Making Beirut v1.0" is the first actual gathering for the hardware maker community in Lebanon. In my opinion, Beirut is not ready for a Maker Fair <yet>, however, and as the name of the exhibition suggests, we would like to promote the maker culture, spread the knowledge and gather the community so that v2.0 will be closer to the full deal.<br />
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During four days many items will be exhibited. I, myself will be exhibiting a couple of items that can be found on my blog and elsewhere. And I can ensure the people attending the exhibition that they will also be an active part of the exhibition where they can play with robots, interact with tables, experiment with photography, and even play with electronics!<br />
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So get your geeky spirit ready, and join the makers at <a href="http://www.karajbeirut.org/" target="_blank">karaj </a>and learn how you can promote and meet a community that is hacking its way into the city as they want to see it. <br />
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<br />Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com1tag:blogger.com,1999:blog-1384219110719459434.post-6151876962217311912012-06-05T19:25:00.000+03:002012-06-08T13:56:07.578+03:00The ShakerBOT: Snakeboard inspired robot<div style="text-align: justify;">
When one thinks about robot locomotion, the first thing that comes to mind are bipedal robots or mobile wheeled robots. This is not the case with Sevag Babikian. As part of a research done by the Mechanical Engineering department at the American University of Beirut, Sevag built a wheeled robot which motion is inspired from the <a href="http://en.wikipedia.org/wiki/Snakeboard" target="_blank">snakeboard</a>. He called it the <a href="http://www.instructables.com/id/The-ShakerBot/" target="_blank"><b>ShakerBot</b></a>. </div>
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<b>What is the ShakerBot made of? </b><br />
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As we can see above, the Shakerbot is made up of the following components:</div>
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- A plexiglass laser cut chassis </div>
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- A central DC motor connected to a 2kg metallic flywheel</div>
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- A couple of DC motors (steering motors) on the front and back. These motors are called steering motors and they are connected to an axle which in turn is connected to friction wheels to guide the robot.</div>
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- A couple of castor wheels on both sides of the robot to support its weight. </div>
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All the motors are connected to quadrature encoders to compute their instantaneous position and speed. Each motor is driven using an L298 based motor driver circuit, capable of driving up to 4A continuously.The brain of the Shakerbot is an <b>Arduino Mega</b> board. The Arduino Mega communicates wirelessly via bluetooth (ARF32 module) to a PC for teleoperation.</div>
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<b>So, how is motion generated on this ShakerBot? </b></h3>
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Have you ever seen a <a href="http://www.youtube.com/watch?v=Ts-nfw-GWcA" target="_blank">snakeboard</a>? Or have you ever felt the urge to kneel on a rotating chair and start turning in order to experience the effects of inertia, or those of dizziness? Well, ShakerBot operates on the same principle. The flywheel generates momentum which drives the robot around. Steering motors, as well as the flywheel, move in a sinusoidal fashion. The motion pattern of the flywheel and of the steering motors are what generate the different robot motions (forward, backward, rotation, parallel park etc.). The mathematics are quite complicated and can be fully understood in this<a href="http://catspaw.its.queensu.ca/bitstream/1974/203/1/1993f_letter.pdf" target="_blank"> publication</a> by Lewis A. et al (1993).</div>
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The following video explains the mechanism better</div>
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The Arduino Mega board does all the complex mathematical and trigonometric equating and controls the DC motors accordingly.<br />
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How does the ShakerBot communicate with the PC? </h3>
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As mentioned above, the computing is done on the Arduino Mega board. However, it is required to have a wireless connection with a PC in order to teleoperate the ShakerBOT and tell it where to go. A couple of months ago I received a bluetooth module from <a href="http://uk.farnell.com/" target="_blank">Farnell electronics</a>. It is the low cost ARF7044A based on the ARF32 bluetooth module manufactured by Adeunis (you can find it on the <a href="http://uk.farnell.com/adeunis/arf7044a/module-arf32-bluetooth-data/dp/1753619" target="_blank">Farnell Electronics website</a>). I decided to help Sevag out in implementing the bluetooth communication on the ShakerBot using this board. For 23<span class="st">£ I can tell you that this <span style="color: black;">chip</span> worked like a charm. We were able to achieve instantaneously a wireless communication, simply by wiring it to the serial Tx and Rx of the Arduino Mega and by connecting it to our laptop's bluetooth.</span></div>
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<tr><td class="tr-caption" style="text-align: center;">The ARF7044 connected to the arduino shield</td></tr>
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<span class="st">I will be using more of this ARF7044 in the future and I will post whatever I find. </span></div>
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<span class="st"><span style="color: black;">On another note</span>, for all the electronics makers, geeks and hackers out there, I discovered lately a website with a large community powered by Farnell electronics that you should check out. It is called <a href="http://www.element14.com/community/index.jspa" target="_blank">element14</a>. </span></div>
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<tr><td class="tr-caption" style="text-align: center;">Sevag and his ShakerBOT</td></tr>
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Concluding thoughts</h3>
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The easiest mechanism for robot locomotion is the <a href="http://en.wikipedia.org/wiki/Differential_%28mechanical_device%29" target="_blank">differential drive mechanism</a>. However if we look at humans we see that we use bipedalism very efficiently. We can walk, run and even climb with minimal energy consumption. This is because we make use of gravity to ease up the locomotion. Up until now, every attempt to mimic human bipedalism on humanoid robot has been very inefficient. This might change as technology as we learn how to fully harbor the physics and dynamics of the system. Same thing can be thought about this ShakerBOT. Humans use snakeboard efficiently, they harbor the momentum generated by their bodies in order to propel. Maybe this ShakerBOT and after plenty of modifications and improvements will turn out to be an efficient locomotion method after all. </div>
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Finally, I am very excited to see the maker movement growing fast in Lebanon. First Mounir and his <a href="http://www.depotbassam.com/2012/04/lebanese-octo-copter-build.html" target="_blank">Octocopter</a> and now Sevag and his ShakerBOT. I can ensure you that there many more creative people just waiting to expose their work!</div>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com1tag:blogger.com,1999:blog-1384219110719459434.post-60185539964726957752012-04-16T23:10:00.000+03:002012-04-18T23:00:02.281+03:00Lebanese OCTO Copter built by Mounir Zoorob<div dir="ltr" style="text-align: left;" trbidi="on">
A few days ago, I bumped into Mounir Zoorob's OCTO copter project. It is a very impressive flying monster that Mounir designed entirely by himself. It is 1m in diameter and it has a 3 axis camera Gimbal, all designed from scratch. Apparently he has spent over 4 months very hard at work to finish it on time. I must say he did a pretty amazing job. So I invited Mounir on DepotBassam to write a small review of his OCTO copter flying machine, and here is his post: </div>
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Before starting, I would like to mention that the materials used are not the best choice. However, since there was nothing available in this part of the world and shipping carbon fiber parts was not possible I had to go with aluminum and Plexi glass instead. (on that subject, review DepotBassam's post on <a href="http://www.depotbassam.com/2011/07/lebanese-electronics-shops-tsop.html" target="_blank">Lebanese electronics shops</a> for more info)<br />
I used 2cm * 2cm * 1 mm aluminum square tubes and the motors are from DIY drones with 35cm wires 2836/9. Each engine has a thrust of 1300g approximately. <br />
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I'm using Ardumega from DIY Drones as the main controller with magnetometer + sonar. So far it has proven to be the best thing I have ever bought for this hobby. i enjoyed it so much i bought it as a kit and soldered everything together<br />
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I designed and laser cut the case from a 3mm black plexiglass to hold both the Ardumega and the receiver.<br />
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As for the motor controllers, I bought 8 25AMP Turnigy ESC's from <a href="http://www.hobbyking.com/" target="_blank">HobbyKing</a>.<br />
I am currently using 11*4.7 props but will go with the 12 later on down the road. All well balanced<br />
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Ardumega will be responsible for the compensation on the roll/pitch axis at the moment. Later on, I will upgrade it to control all three axis. <br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkO4tWkn6xFWQl1yLXBh1rxX6C2sTZ6RWy8egnX-Eej0B8uxF8xCTLuhm7pg1eSVVWH5wC6t0AaWZeEVRTeLXjzYMfeoz1wse7XK2qOgbPLVqTOJyiCXvqnsOjUPB_HAq0fOuG6yIEpaV6/s1600/3.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgkO4tWkn6xFWQl1yLXBh1rxX6C2sTZ6RWy8egnX-Eej0B8uxF8xCTLuhm7pg1eSVVWH5wC6t0AaWZeEVRTeLXjzYMfeoz1wse7XK2qOgbPLVqTOJyiCXvqnsOjUPB_HAq0fOuG6yIEpaV6/s320/3.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><span style="font-size: small; text-align: left;">This is my camera gimbal. It currently has 2 active axis , but later on I will upgrade it to 3 axis.</span>
<span style="font-size: small; text-align: left;">Currently I'm working on finalizing roll and pitch, but I am still waiting for the right parts to arrive. </span> </td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXoOAYrJ7c9mnSG_tyj3xJr-IokMlsnOSS0Udg5E_Myp08aBYxypS91wtzFVPGOnhcyGcVzHbeOP3kSkReM-6i1tzy1TdVIq5iph9qyCE3TgRAtfIIz11ScY-8PTJiOTIVLgnPBTR2nFql/s1600/7.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgXoOAYrJ7c9mnSG_tyj3xJr-IokMlsnOSS0Udg5E_Myp08aBYxypS91wtzFVPGOnhcyGcVzHbeOP3kSkReM-6i1tzy1TdVIq5iph9qyCE3TgRAtfIIz11ScY-8PTJiOTIVLgnPBTR2nFql/s320/7.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Wires were also taken into consideration during the design phase :) very neat :) </td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzoqF0Cc_WzRVF9Pq6vd6gVIs6miS03pXbtkmlhYojtZyJkZuun8ADGlP1GiSo1-h-2BTg_Jg8NhVgkejDIga67yoaMBc_kT1pmtzvdTOP9AsieDLDnLFQd1dgcDv2AzX20tUnNj8EKpGa/s1600/6.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhzoqF0Cc_WzRVF9Pq6vd6gVIs6miS03pXbtkmlhYojtZyJkZuun8ADGlP1GiSo1-h-2BTg_Jg8NhVgkejDIga67yoaMBc_kT1pmtzvdTOP9AsieDLDnLFQd1dgcDv2AzX20tUnNj8EKpGa/s320/6.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Wires from the ESC's to main power source are all well soldered and added heat shrink.</td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3IdkKzubn_aegjK-rNBKQeOT2nPpDiCLWpJS3VbpXmHRmMnu0EQJOuMj8pFompuGvkr_SVBlInrttP1UR5kSVQTZ-Ymegy5p6er6tO2S5L7VGRpmhDNOf7WoND6ozywkr07xiahKuSbKi/s1600/8.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="213" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3IdkKzubn_aegjK-rNBKQeOT2nPpDiCLWpJS3VbpXmHRmMnu0EQJOuMj8pFompuGvkr_SVBlInrttP1UR5kSVQTZ-Ymegy5p6er6tO2S5L7VGRpmhDNOf7WoND6ozywkr07xiahKuSbKi/s320/8.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><div class="separator" style="clear: both; text-align: center;">
Here's the OCTO almost ready for a test flight :)</div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3ExOuRr08pYpdOVBwHRErhcQwucm136W4J7_msRMktgk3jbZuxGtvosxwoIjtQKW1Y40nYiCeDCa0-yLdjKnKP1jUOM7zfmUEQXqmU1GNqi22E-LYxDhyH_Vx9NkhWQX0dk09uYtU_P0R/s1600/9.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg3ExOuRr08pYpdOVBwHRErhcQwucm136W4J7_msRMktgk3jbZuxGtvosxwoIjtQKW1Y40nYiCeDCa0-yLdjKnKP1jUOM7zfmUEQXqmU1GNqi22E-LYxDhyH_Vx9NkhWQX0dk09uYtU_P0R/s400/9.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><br />
Here is the OCTO after couple of flights. I modified the design of the Gimbal and I integrated a new landing gear design on it</td></tr>
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I promise the next design will be more elegant. With the cash at hand and the time this is the best I was able to come up with. <br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHNpSud2idaEyTJwTJIjunNjZ2U0Q92StI_fHw68evNNg_taDpHcOsyoYKWTWTm-CQzfoSiqaRlx0_o4GtcQF-bRyKvZp5lU5ToMfm71FitGy9KCyMBP-CpHRbj2iN2z5RNSU05q-rPKBG/s1600/10.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="356" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjHNpSud2idaEyTJwTJIjunNjZ2U0Q92StI_fHw68evNNg_taDpHcOsyoYKWTWTm-CQzfoSiqaRlx0_o4GtcQF-bRyKvZp5lU5ToMfm71FitGy9KCyMBP-CpHRbj2iN2z5RNSU05q-rPKBG/s640/10.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Here is a sample picture from the video I'm taking from the OCTO</td></tr>
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<div style="text-align: center;">
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<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/J94gKOtfC24" width="420"></iframe></div>
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<div class="separator" style="clear: both; text-align: left;">
Here is the first video from the OCTO, of course it looks better now but this is just a sample.</div>
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<div style="text-align: center;">
<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/zOFz3ZwD-IY" width="420"></iframe></div>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGQzH2TpBxWzcl8gXWQM-V7bFqod6phhfutrcP60LlcHWtnz-dWlIjbfP37TdwzpWi0FYe5_qB3-FpUpf8LoJa1v58fP65hXVNxDiytTDt6clQ1vh5dwXCVzS7HHRWt-l9N2gBxfYS8ON7/s1600/beer+lift.jpg" style="margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiGQzH2TpBxWzcl8gXWQM-V7bFqod6phhfutrcP60LlcHWtnz-dWlIjbfP37TdwzpWi0FYe5_qB3-FpUpf8LoJa1v58fP65hXVNxDiytTDt6clQ1vh5dwXCVzS7HHRWt-l9N2gBxfYS8ON7/s1600/beer+lift.jpg" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">For those who love beer, here's one for you :) Note: I got rid of that beard</td></tr>
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Feel free to ask me anything, your feedback is important to me. It better be a good one though!</div>Unknownnoreply@blogger.com6tag:blogger.com,1999:blog-1384219110719459434.post-63481176476746361902012-04-14T14:05:00.000+03:002012-04-14T17:55:21.585+03:00Wall Mounted Double Pendulum for Experimental Photography(or how we went to outer space shot some galaxies and came back) <br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsUbYYHz07m9jx6-0F80bH9IUyauwrZ7XrdkdTFgmbTkd-zZfzgJHHjspvTS3_1UKAbu5LtH0cpJv36_9tzmJ09wb5mDA4y4OzO_8CinNCD9FQ7FxA0OHsPUtwazSxc2JExLxf5wL2LpCF/s1600/IMG_0254.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="431" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgsUbYYHz07m9jx6-0F80bH9IUyauwrZ7XrdkdTFgmbTkd-zZfzgJHHjspvTS3_1UKAbu5LtH0cpJv36_9tzmJ09wb5mDA4y4OzO_8CinNCD9FQ7FxA0OHsPUtwazSxc2JExLxf5wL2LpCF/s640/IMG_0254.jpg" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Through the lens of <a href="http://www.abirghattas.com/">Abir Ghattas</a></td></tr>
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My first interest in chaotic behavior can be traced back to <a href="http://www.depotbassam.com/2011/08/chaos-theory-simulating-double-pendulum.html">this post</a>. This time however, instead of simply developing a simulator I decided to build a real double pendulum. Watching a double pendulum dance erratically was worth a million simulation. If you are follower of this blog you will realize instantly that I could never let this opportunity pass without transforming it into some sort of a crazy experiment (-mostly photographic-).<br />
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The first step in the process was the design of the pendulum. The dimensions were chosen such as to maximize the chaotic behavior. <a href="http://dl.dropbox.com/u/4924768/DoublePendulum/DoublePendulum.dwg">Click here</a> to download the AutoCAD .dwg file.<br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4bkPUJNevH5ITz8nUPVL4Z9tgPvxjfyhbUvrQLcOO26A2fF5kYMpkI2b1Xx_S-x0s920SaRDiMeD5XqGO63zLsKFa8Eo2e6UlLaW9_ncukRt0d3TTKG_E72GON2RDAaw-pDz6tIRbBT-Z/s1600/DoublePendulum.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="452" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEg4bkPUJNevH5ITz8nUPVL4Z9tgPvxjfyhbUvrQLcOO26A2fF5kYMpkI2b1Xx_S-x0s920SaRDiMeD5XqGO63zLsKFa8Eo2e6UlLaW9_ncukRt0d3TTKG_E72GON2RDAaw-pDz6tIRbBT-Z/s640/DoublePendulum.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">All dimensions are in cm</td></tr>
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The material was chosen to be transparent 2mm thick plexiglass (4mm would have been ideal-but it was not available). The reason I chose to use a transparent material was so that the light can pass through in photography. I would definitely choose another material if I was using the pendulum for decorative purposes.</div>
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As for the components needed: </div>
<div style="text-align: left;">
- 6mm ball bearings x4</div>
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- 6mm Hex Screw with nuts and washers x2</div>
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- 3mm wall mounting screws and screw anchors x2</div>
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The following slideshow displays the assembly process</div>
<embed flashvars="host=picasaweb.google.com&captions=1&hl=en_US&feat=flashalbum&RGB=0x000000&feed=https%3A%2F%2Fpicasaweb.google.com%2Fdata%2Ffeed%2Fapi%2Fuser%2F113000065480657015081%2Falbumid%2F5731179438777994337%3Falt%3Drss%26kind%3Dphoto%26hl%3Den_US" height="400" pluginspage="http://www.macromedia.com/go/getflashplayer" src="https://picasaweb.google.com/s/c/bin/slideshow.swf" type="application/x-shockwave-flash" width="600"></embed><br />
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Here's a video of the double pendulum in action<br />
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<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/YejjGtv28dg" width="560"></iframe></div>
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After the assembly, <a href="http://www.abirghattas.com/" target="_blank">Abir Ghattas</a> and <a href="http://www.flickr.com/photos/patrickas/" target="_blank">Patrick Abi Salloum</a> came over for the photoshoot. We used LEDs of different colors connected to 3V coin batteries and we took long exposure pictures in the dark.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh387mjampozYpLymaZXRMyyga-p_oM3Yr3dreSemznn3hyphenhyphenDxsN5v_3eD26QtZnza7D_rAJ-1VNyn0zbnOqBA7KZZ-sukomSPo9ZEi78DK9fFaPDIrEyfDxIc4d5h_x3R6BEp6U33dknMCU/s1600/The+picture+taking.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="290" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh387mjampozYpLymaZXRMyyga-p_oM3Yr3dreSemznn3hyphenhyphenDxsN5v_3eD26QtZnza7D_rAJ-1VNyn0zbnOqBA7KZZ-sukomSPo9ZEi78DK9fFaPDIrEyfDxIc4d5h_x3R6BEp6U33dknMCU/s640/The+picture+taking.png" width="640" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Left to Right: (1) Abir painting the pictures with LEDs (2)focusing (3) Patrick vs. Abu Ali</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEix17vnsxVjdfN48yYEIZySAgP6_k3NIIWifZz9HXTGD2DChJJhrfBN1JvEAKhQvrm-eS8OCoV9GKyB5WbUdKarvN6lBs75s4kxqaixF3MVs1Y-0Rj4yxfv8xMCR2q7-Gsx4XNaooLqNk2q/s1600/Abzzy.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEix17vnsxVjdfN48yYEIZySAgP6_k3NIIWifZz9HXTGD2DChJJhrfBN1JvEAKhQvrm-eS8OCoV9GKyB5WbUdKarvN6lBs75s4kxqaixF3MVs1Y-0Rj4yxfv8xMCR2q7-Gsx4XNaooLqNk2q/s640/Abzzy.jpg" width="446" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Courtesy of <a href="http://www.flickr.com/photos/patrickas/" target="_blank">Patrick Abi Salloum</a></td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm2YtGjI_ojugKkdkbemycbNYFqRKAl49HHw6Spu6ZOO2o9pTIVux_GrxWupxO5CTzuH_fhHEDJafMOeen54LV22vrRJRLQgeOaYVbnzTjGfse_rn8fRGEoUVOxKE9SCHMaXd8Hkp8P4K5/s1600/sm080_a.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="640" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhm2YtGjI_ojugKkdkbemycbNYFqRKAl49HHw6Spu6ZOO2o9pTIVux_GrxWupxO5CTzuH_fhHEDJafMOeen54LV22vrRJRLQgeOaYVbnzTjGfse_rn8fRGEoUVOxKE9SCHMaXd8Hkp8P4K5/s640/sm080_a.jpg" width="454" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">"Angel of Death" courtesy of <a href="http://www.flickr.com/photos/patrickas/" target="_blank">Patrick Abi Salloum</a></td></tr>
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For the result check Abir's website: <a href="http://abirghattas.com/double-pendulum-experimental-shoot/">http://abirghattas.com/double-pendulum-experimental-shoot/</a><br />
and Patrick's flickr: <a href="http://www.flickr.com/photos/patrickas/7072749767/in/photostream">http://www.flickr.com/photos/patrickas/7072749767/in/photostream</a>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com2Beirut, Lebanon33.8886289 35.495479433.8754479 35.4757384 33.9018099 35.515220400000004tag:blogger.com,1999:blog-1384219110719459434.post-57633263428711546682012-03-26T02:36:00.000+03:002012-04-09T02:43:38.186+03:00The Bathroom Illusion<div style="text-align: center;">
Last month we moved to a new workshop. The new space used to be a storage house, so you can imagine the mess. It is old and required lots of renovation work. Now you might think that the renovation work was boring... well... not for me.</div>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1gWcz_o-G1R_u0pvKIrwXGdRIo1MJlDTrc-Ao7i2cLJ7xfxpgqRvlQjilezjjfMfFvqtvw6eoRjDl7jFvy2jBtAs5Fh-rH_twO2aVgRReh-S3_ToDmDjOYaWYj140ncaeWA-cgBdiwWTH/s1600/Bathroom_window.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh1gWcz_o-G1R_u0pvKIrwXGdRIo1MJlDTrc-Ao7i2cLJ7xfxpgqRvlQjilezjjfMfFvqtvw6eoRjDl7jFvy2jBtAs5Fh-rH_twO2aVgRReh-S3_ToDmDjOYaWYj140ncaeWA-cgBdiwWTH/s400/Bathroom_window.jpg" width="298" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">One particular issue that needed urgent attention was the bathroom door. It had a fully transparent window.</td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiOgwOY1dg-TPKQYsWtXoDKM_8CFQ9Vq13JmKPZQaSCPKc4072AceisVnXFHHaQFZTdTaRpBZO7Y4sKEvURQpNquK3bZcxBw6utFHrH6qdE8cH7tw6nIze7IHNdRrfbv4XWgWSZWTdIKpa/s1600/Piss1.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiiOgwOY1dg-TPKQYsWtXoDKM_8CFQ9Vq13JmKPZQaSCPKc4072AceisVnXFHHaQFZTdTaRpBZO7Y4sKEvURQpNquK3bZcxBw6utFHrH6qdE8cH7tw6nIze7IHNdRrfbv4XWgWSZWTdIKpa/s400/Piss1.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">One day my friend was having a piss..</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSStxWLU8G8vb_2WmF_-_LY2gNjGm43JRw_ELh3dKCeyS5vXSKdm4EUzzCym-8dCP4d8HedLlBslceSEwWeSrJloi1YXhsoYwhfzbhswcVjWUU3gmmPXSY2qwBDAgifzNvLNjZD3rzHtfi/s1600/Piss2.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjSStxWLU8G8vb_2WmF_-_LY2gNjGm43JRw_ELh3dKCeyS5vXSKdm4EUzzCym-8dCP4d8HedLlBslceSEwWeSrJloi1YXhsoYwhfzbhswcVjWUU3gmmPXSY2qwBDAgifzNvLNjZD3rzHtfi/s400/Piss2.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I snapped a picture..</td></tr>
</tbody></table>
<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGlSLB3wYszqqYAPd0pU0Ys2MqJFBxAc2W6qHyfent0MUQ7Rjkf66Z11XJWf2XhGGsPB2TUTGG8YGyYtkQNujMEUNHLdIY5zEOBLyQjBJ0M6kIQbBS7qGLDYwBN2UHSenUVHanEGeoqTIW/s1600/ThePicture.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgGlSLB3wYszqqYAPd0pU0Ys2MqJFBxAc2W6qHyfent0MUQ7Rjkf66Z11XJWf2XhGGsPB2TUTGG8YGyYtkQNujMEUNHLdIY5zEOBLyQjBJ0M6kIQbBS7qGLDYwBN2UHSenUVHanEGeoqTIW/s400/ThePicture.jpg" width="298" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">I developed the picture..</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio6vkbCBOtvRONTr0F13qcLSBV6kQiDM9dEFeoLQDgRSXl2922Ot_3uXDUy53w6k97lH7jf9k48D90TgX_fdCSZfdFenoOlFMDKdz_XKxhbwifq1s6j5hHRL-zkPCiX8GKmpMPr5hnUL4_/s1600/TheOutcome.jpg" imageanchor="1"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEio6vkbCBOtvRONTr0F13qcLSBV6kQiDM9dEFeoLQDgRSXl2922Ot_3uXDUy53w6k97lH7jf9k48D90TgX_fdCSZfdFenoOlFMDKdz_XKxhbwifq1s6j5hHRL-zkPCiX8GKmpMPr5hnUL4_/s400/TheOutcome.jpg" width="299" /></a></td></tr>
<tr align="center"><td class="tr-caption">And sticked it to the window</td></tr>
</tbody></table>
<div style="text-align: center;">
And now my friend is always having a piss </div>
<br />
<br />
<span id="goog_1158446940"></span><span id="goog_1158446941"></span>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com6tag:blogger.com,1999:blog-1384219110719459434.post-33870343966110295242012-03-01T01:14:00.002+02:002012-03-10T12:32:04.884+02:00Class B Push-Pull Amplifier Design for DC Motor Analog Drive<div class="separator" style="clear: both; text-align: left;">
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I am currently involved in a project that requires analog speed control of a DC motor. One very popular method to achieve control of DC motors requires the use of a PWM signal along with an Hbridge circuit. <a href="http://modularcircuits.tantosonline.com/blog/articles/h-bridge-secrets/h-bridges-the-basics/">Modular circuit</a> website provides a great resource for the Hbridge circuit and explains thoroughly different PWM driving techniques like Sign-Magnitude and Lock Anti-Phase Drive methods. However, and after doing a basic online search, I barely found any good resources on analog DC motor drives. There are many reasons for this mainly because switching drive methods are generally much more efficient than their analog counterparts and PWM signals are easily generated using microcontrollers as compared to the use of DAC for analog control. This does not mean that analog drive is obsolete as it is still the preferred method in some applications such as motor frequency response, continuous time control, and applications that are sensitive to the electromagnetic interference (EMI) that can be generated by a PWM switching circuit.<br />
<br />
A famous method for transforming an analog signal into switching PWM signal is done using a<a href="http://en.wikipedia.org/wiki/Class-D_amplifier"> class-D amplifier</a> (switching amplifier). However such an amplifier design is complicated and requires lots of components. On the other hand, there are some commercially available power amplifiers such as the LM675, L165. Such ICs are a bit expensive and not widely available for the hobbyist to use.<br />
In this post I will be reviewing DIY analog circuit designs to drive DC motors using BJT power transistors. This requires good knowledge of BJT transistors. If the terms base, collector, emitter, npn, pnp, cut-off, active and saturation regions do not mean anything to you, then maybe you should consider doing a BJT transistor research before continuing to read here. <br />
<br />
I will be using a TIP31 <b>npn</b> transistor which has the following characteristics:<br />
- Current gain: hfe=β= 50<br />
- Collector-Emitter saturation voltage : Vce(sat)=1.2V<br />
- Cut-off voltage Vbe(on) = 1.8V [according to the context-this will be called Vbe from now on]<br />
I will be using also TIP32 which is the complimentary <b>pnp</b> transistor of the TIP31.<br />
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<b>Common Emitter Configuration </b><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpAnfwmtUE_vpdzZyXPq1okIBsReoZMHXGBTXQ3lB6uL3P75T290exCKL3q8qTNGAUkGqv57UtAXiifFCEZcfuXP0LCnfoM1ptDZcQmeJSlgPI4JiFJHItUXv-mqtvSi4zCF-W_fiG2guj/s1600/CE.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgpAnfwmtUE_vpdzZyXPq1okIBsReoZMHXGBTXQ3lB6uL3P75T290exCKL3q8qTNGAUkGqv57UtAXiifFCEZcfuXP0LCnfoM1ptDZcQmeJSlgPI4JiFJHItUXv-mqtvSi4zCF-W_fiG2guj/s200/CE.png" width="195" /></a></div>
In this configuration we can achieve current control for the motor. Since for a DC motor the torque is proportional to current (T=K*ic where K is a constant that depends on the motor's winding configuration), torque control can be achieve using this circuit. While in active mode, the equation relating ic to Vin can be found (note Vbe = Vbe(on))<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfn_cm%20i_c%20=%20%5Cbeta%20i_b%20&=&%20%5Cbeta%20%5Cfrac%7BV_%7Bin%7D-V_%7Bbe%7D%7D%7BR_b%7D%5C%5C" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfn_cm%20i_c%20=%20%5Cbeta%20i_b%20&=&%20%5Cbeta%20%5Cfrac%7BV_%7Bin%7D-V_%7Bbe%7D%7D%7BR_b%7D%5C%5C" title="\fn_cm i_c = \beta i_b &=& \beta \frac{V_{in}-V_{be}}{R_b}\\" /></a></div>
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfn_cm%20T%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_%7Bbe%7D%29" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfn_cm%20T%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_%7Bbe%7D%29" title="\fn_cm T = \frac{K\beta}{R_b}(V_{in}-V_{be})" /></a></div>
Let us understand this model intuitively:<br />
<ul>
<li>For Vin<Vbe transistor is in cut-off region and motor is off. </li>
<li>For Vin>Vbe and Vce>Vce(sat) transistor is in active region, motor torque T is proportional to Vin. </li>
<li>As we increase Vin, ib increases which means ic increases and Vce decreases. </li>
<li>For Vin>>Vbe and Vce=Vce(sat):saturation region, motor reaches its maximum torque/speed capacity. </li>
</ul>
If we follow the DC motor's mechanical model developed in the following <a href="http://www.engin.umich.edu/group/ctm/examples/motor/motor.html">Carnegie Melon tutorial</a> and assuming the only torque applied on the motor shaft is that of shaft inertia (Jm) and damping (B) we can compute the transfer function of the speed (w) versus ΔV=Vin-Vbe<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfn_cm%20T-B%20%5Comega%20=%20J_m%5Cdot%20%5Comega%5C%5C%20sJ_m%20%5Comega%20@plus;%5Comega%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%5CDelta%20V%5C%5C%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D=%5Cfrac%7B%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%7D%7BsJ_m%20@plus;%20B%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfn_cm%20T-B%20%5Comega%20=%20J_m%5Cdot%20%5Comega%5C%5C%20sJ_m%20%5Comega%20+%5Comega%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%5CDelta%20V%5C%5C%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D=%5Cfrac%7B%5Cfrac%7BK%5Cbeta%7D%7BR_b%7D%7D%7BsJ_m%20+%20B%7D" title="\fn_cm T-B \omega = J_m\dot \omega\\ sJ_m \omega +\omega = \frac{K\beta}{R_b}\Delta V\\ \frac{\omega}{\Delta V}=\frac{\frac{K\beta}{R_b}}{sJ_m + B}" /></a></div>
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According to the transfer function the steady state relationship between speed and voltage in the case of no load condition is <br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfn_cm%20%5Comega%20_%7Bss%7D%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_bB%7D%28V_%7Bin%7D-V_%7Bbe%7D%29" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfn_cm%20%5Comega%20_%7Bss%7D%20=%20%5Cfrac%7BK%5Cbeta%7D%7BR_bB%7D%28V_%7Bin%7D-V_%7Bbe%7D%29" title="\fn_cm \omega _{ss} = \frac{K\beta}{R_bB}(V_{in}-V_{be})" /></a></div>
According to this result, decreasing Rb would cause the speed to go higher. Of course this method has its pros and cons:<br />
<ul>
<li>pro: Assuming β is constant we can achieve linear current (torque) control of DC motor</li>
</ul>
<ul>
<li>con: The model is highly dependent on the current gain β (hfe) which varies alot specially for high power BJT (in the case of TIP31 it varies between 10 and 100). Hence the model is non linear! </li>
</ul>
<b>Common Collector Configuration </b>(also called Emitter-Follower)<b><br />
</b><br />
In order to cancel the effect of β on the system we connect the motor in a common collector configuration. In this configuration, the motor is connected to the emitter of the BJT as shown in the following figure. This configuration is called emitter follower because the voltage on the emitter will always be following that of the input with a voltage drop of Vbe. So the gain of this configuration is a bit less than 1. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifo7K4UnLZY44fHU5Qk7sxGL9OcL9Dm8gWIPL6b0zenft14bByMGQG8gVSCpNiVJI8oSfBq82Phh6jjTF0jOwG1ebUp11M0y5iDf-2z-FKOVbHeR7co-mlxJXatE1UZToUuv1lXIX6qMoQ/s1600/CC.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifo7K4UnLZY44fHU5Qk7sxGL9OcL9Dm8gWIPL6b0zenft14bByMGQG8gVSCpNiVJI8oSfBq82Phh6jjTF0jOwG1ebUp11M0y5iDf-2z-FKOVbHeR7co-mlxJXatE1UZToUuv1lXIX6qMoQ/s200/CC.png" width="195" /></a></div>
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Again, and to evaluate the circuit, we need to find the transfer function ω/ΔV where ΔV=Vin-Vbe. <br />
In this configuration when the transistor is turned on, Ve=Vb-Vbe. Knowing that ΔV=Vin-Vbe, the relation between the motor current, motor voltage and Vin can be found: <br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20i_e=%281@plus;%5Cbeta%29i_b=%5Cfrac%7B1@plus;%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_b%29=%5Cfrac%7B1@plus;%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_e-V_%7Bbe%7D%29=%5Cfrac%7B1@plus;%5Cbeta%7D%7BR_b%7D%28%5CDelta%20V-V_e%29" style="margin-left: auto; margin-right: auto;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20i_e=%281+%5Cbeta%29i_b=%5Cfrac%7B1+%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_b%29=%5Cfrac%7B1+%5Cbeta%7D%7BR_b%7D%28V_%7Bin%7D-V_e-V_%7Bbe%7D%29=%5Cfrac%7B1+%5Cbeta%7D%7BR_b%7D%28%5CDelta%20V-V_e%29" title="\small \fn_cm i_e=(1+\beta)i_b=\frac{1+\beta}{R_b}(V_{in}-V_b)=\frac{1+\beta}{R_b}(V_{in}-V_e-V_{be})=\frac{1+\beta}{R_b}(\Delta V-V_e)" /></a></td></tr>
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</tbody></table>
According to the <a href="http://www.engin.umich.edu/group/ctm/examples/motor/motor.html"><u>mechanical model</u></a> of the motor we know that the motor torque is equal to<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20T=%20J_m%20%5Cdot%5Comega%20@plus;B%20%5Comega" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20T=%20J_m%20%5Cdot%5Comega%20+B%20%5Comega" title="\small \fn_cm T= J_m \dot\omega +B \omega" /></a></div>
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Since T=K*ie and performing the Laplace transform we obtain<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20i_e=%5Cfrac%7B1%7D%7BK%7D%20%28J_m%20s%20@plus;%20B%29%20%5Comega" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20i_e=%5Cfrac%7B1%7D%7BK%7D%20%28J_m%20s%20+%20B%29%20%5Comega" title="\small \fn_cm i_e=\frac{1}{K} (J_m s + B) \omega" /></a></div>
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Equating the two equations we get the following relation:<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20V_e%20=%20%5CDelta%20V%20-%20%5Cfrac%7BR_b%7D%7B%281@plus;%5Cbeta%29K%7D%28J_m%20s@plus;B%29%5Comega" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20V_e%20=%20%5CDelta%20V%20-%20%5Cfrac%7BR_b%7D%7B%281+%5Cbeta%29K%7D%28J_m%20s+B%29%5Comega" title="\small \fn_cm V_e = \Delta V - \frac{R_b}{(1+\beta)K}(J_m s+B)\omega" /></a></div>
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The <a href="http://www.engin.umich.edu/group/ctm/examples/motor/motor.html">electrical model</a> of the motor gives<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20V_e%20=%20Ri_e%20@plus;%20L%5Cfrac%7Bdi_e%7D%7Bdt%7D%20@plus;%20K%5Comega" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20V_e%20=%20Ri_e%20+%20L%5Cfrac%7Bdi_e%7D%7Bdt%7D%20+%20K%5Comega" title="\small \fn_cm V_e = Ri_e + L\frac{di_e}{dt} + K\omega" /></a></div>
<br />
Where R and L are the internal resistance and inductance of the motor coils. We are assuming in here that the motor is ideal and the generated EMF constant (K) is equal to that of the torque/current proportionality constant. Combining the electrical model with the previous equations of Ve and ie we obtain the following transfer function<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D%20=%20%5Cfrac%7BK%7D%7BJ_mLs%5E2%20@plus;%20%28BL@plus;J_mR@plus;J_m%5Cfrac%7BR_b%7D%7B1@plus;%5Cbeta%7D%29s@plus;%28%5Cfrac%7BR_bB%7D%7B1@plus;%5Cbeta%7D@plus;BR@plus;K%5E2%29%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D%20=%20%5Cfrac%7BK%7D%7BJ_mLs%5E2%20+%20%28BL+J_mR+J_m%5Cfrac%7BR_b%7D%7B1+%5Cbeta%7D%29s+%28%5Cfrac%7BR_bB%7D%7B1+%5Cbeta%7D+BR+K%5E2%29%7D" title="\small \fn_cm \frac{\omega}{\Delta V} = \frac{K}{J_mLs^2 + (BL+J_mR+J_m\frac{R_b}{1+\beta})s+(\frac{R_bB}{1+\beta}+BR+K^2)}" /></a></div>
<br />
From this transfer function we notice that if we choose Rb = 0 the effect of β on the motor is canceled. The transfer function then becomes<br />
<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Csmall%20%5Cfn_cm%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D%20=%20%5Cfrac%7BK%7D%7BJ_mLs%5E2%20@plus;%20%28BL@plus;J_mR%29s@plus;%28BR@plus;K%5E2%29%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Csmall%20%5Cfn_cm%20%5Cfrac%7B%5Comega%7D%7B%5CDelta%20V%7D%20=%20%5Cfrac%7BK%7D%7BJ_mLs%5E2%20+%20%28BL+J_mR%29s+%28BR+K%5E2%29%7D" title="\small \fn_cm \frac{\omega}{\Delta V} = \frac{K}{J_mLs^2 + (BL+J_mR)s+(BR+K^2)}" /></a></div>
<br />
This is exactly the transfer function of a DC motor. However we haven't considered yet the rotation of the motor in both directions (Clockwise CW and counterclockwise CCW)<br />
<br />
<b>Class B Push-Pull Amplifier</b><b><br />
</b>In order to be able to rotate the motor in both clockwise and counterclockwise directions we should be capable of providing a negative current to the motor. This can be achieved using a push-pull amplifier. A push pull amplifier is a Class B type of amplifier that either drives a positive or a negative current into a load. It consist of a pair of complimentary transistors, in our case NPN and PNP BJT transistors, connected in common collector configuration.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyhIOru0iveQKBB2mIwRHx208eFyBI4DtiA0bVCJR4NpA0D-AUBLSGNpD8sG2ye75acG7GnbwRzydiXZXAKvZI-ByrO1NEZTanKkqGSokoOhe7I05g7jz0pa9rCAURBSEM0rzU5RhprEBN/s1600/PushPull_noamp.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiyhIOru0iveQKBB2mIwRHx208eFyBI4DtiA0bVCJR4NpA0D-AUBLSGNpD8sG2ye75acG7GnbwRzydiXZXAKvZI-ByrO1NEZTanKkqGSokoOhe7I05g7jz0pa9rCAURBSEM0rzU5RhprEBN/s200/PushPull_noamp.png" width="195" /></a></div>
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When +Vcc>Vin>Vbe the upper transistor (NPN) is in active region and the lower transistor (PNP) would be in cutoff region. When -Vcc<Vin<-Vbe the lower transisor (PNP) will be in active region and the upper one will be in cutoff. The same theory developed in the previous section can be applied in here. <br />
In order to be able to drive the transistors from a high output impedance source (potentiometer - DAC etc.) we need an impedance matching device. This can be achieved using a UA741 op-amp. The feedback for the op-amp needs to be implemented depending on the gain needed. In our case unity gain is required. <br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPTjibJWV7zPsXH9UgObCZCZUSJ0w3a1w_0fDKw68OwHZyOfDrrnKrgFBm4w-E8Qz1s6ouPjzmoydoaASnKxNIdWquPp1BVrtgQt4x0vXt8QpcthdRmupPDSu2abEFlPVOQjZoA0wnCc37/s1600/PushPull_amp_nofb.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="206" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgPTjibJWV7zPsXH9UgObCZCZUSJ0w3a1w_0fDKw68OwHZyOfDrrnKrgFBm4w-E8Qz1s6ouPjzmoydoaASnKxNIdWquPp1BVrtgQt4x0vXt8QpcthdRmupPDSu2abEFlPVOQjZoA0wnCc37/s400/PushPull_amp_nofb.png" width="400" /></a></div>
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In order to test the class B push-pull amplifier I devised a setup consisting of a DC motor of maximum speed 30RPM connected to a quadrature encoder to measure speed. The data acquisition is accomplished using a dspic30F4012 microcontroller. Running at 120Mhz and 30MIPS this dspic computes the instantaneous velocity and communicates serially with a Matlab code in order to display in real time this velocity. I connected a potentiometer to the input of the amplifier. I would set the pot at a certain voltage and then wait for steady state condition to measure the velocity of the motor. <br />
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<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7pb-qs1iUicb02dFcvXDc_DTRxi0Nn7tkt4F4BW5M5aL16uvVXrp6w10hLprnRcn_D85WX-JZ9PlC6UgopZNdx6BghidvUjL6-n6lsCiS7IsgW9XnQA1S4X2k_WOdRF_Idc4l2bgDz8Mh/s1600/20120220_233713.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh7pb-qs1iUicb02dFcvXDc_DTRxi0Nn7tkt4F4BW5M5aL16uvVXrp6w10hLprnRcn_D85WX-JZ9PlC6UgopZNdx6BghidvUjL6-n6lsCiS7IsgW9XnQA1S4X2k_WOdRF_Idc4l2bgDz8Mh/s400/20120220_233713.jpg" width="400" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">The amplifier/DC motor/encoder/acquisition setup used for the experimentation</td></tr>
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The following plot shows the RPM vs voltage (Vin) curve for the Class B push pull amplifier design shown above.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCXOeaFTWsgQ2RMq0hTirG5AS74ufRE0knoyMvb4I0T0ene39_jhVrO9EXkBi3iaNJ7N9gUCdHOHwTxj452DLHA2-VkwccrjUtC0AGZgjVJ9kYzlrju-iqMkwMrG1-mMDEEngv6KC8nerd/s1600/speed_vs_v1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="387" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjCXOeaFTWsgQ2RMq0hTirG5AS74ufRE0knoyMvb4I0T0ene39_jhVrO9EXkBi3iaNJ7N9gUCdHOHwTxj452DLHA2-VkwccrjUtC0AGZgjVJ9kYzlrju-iqMkwMrG1-mMDEEngv6KC8nerd/s640/speed_vs_v1.png" width="640" /></a></div>
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We notice from this plot that there is a dead zone around 0V. This dead zone is called "<a href="http://en.wikipedia.org/wiki/Crossover_distortion">crossover distortion</a>" in the literature. This is obviously due to base-emitter voltage necessary for the NPN transistor to be in the active region (in the case of positive Vin) and for the PNP transistor to be in the active region (in the case of negative Vin). In the case of TIP31 and TIP32 this crossover distortion is of about 2Vbe=2*1.8=3.6volts. This is not desirable at all since it provides non-linearity that will cause the frequency response analysis or the closed loop control to fail.<br />
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In the following allaboutcircuits.com <a href="http://www.allaboutcircuits.com/vol_6/chpt_6/10.html">article</a> a solution for this crossover distortion was suggested which consists of connecting the op-amp with the negative feedback in the following manner<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXg2cGM4pVDuHB2A62Ym1gDQKKptmRY0LF0RO9pOlVIGUulNd-wCuRNhLoQJE6XGMp2TZeG2PdO_uFGRYKFxu3n3XRndpUzFoEkEEdak_Kr70nNyY1IY71sJeyj5Nncd2soDgEj6gLpSx/s1600/PushPull_amp_fb.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="211" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgUXg2cGM4pVDuHB2A62Ym1gDQKKptmRY0LF0RO9pOlVIGUulNd-wCuRNhLoQJE6XGMp2TZeG2PdO_uFGRYKFxu3n3XRndpUzFoEkEEdak_Kr70nNyY1IY71sJeyj5Nncd2soDgEj6gLpSx/s400/PushPull_amp_fb.png" width="400" /></a></div>
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Without any loss of generality and in order to understand better this circuit we are going to analyze the NPN half of it. A is the gain of the amplifier. <br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfrac%7BV_o%7D%7BV_%7Bin%7D-V_e%7D=A%5C%5C%20V_%7Bbe%7D=V_o-V_e=A%28V_%7Bin%7D-V_e%29-V_e=AV_%7Bin%7D-%281@plus;A%29V_e" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfrac%7BV_o%7D%7BV_%7Bin%7D-V_e%7D=A%5C%5C%20V_%7Bbe%7D=V_o-V_e=A%28V_%7Bin%7D-V_e%29-V_e=AV_%7Bin%7D-%281+A%29V_e" title="\frac{V_o}{V_{in}-V_e}=A\\ V_{be}=V_o-V_e=A(V_{in}-V_e)-V_e=AV_{in}-(1+A)V_e" /></a></div>
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Assuming Vin=ε is the voltage responsible for switching the transistor from the cut-off region to the active region. Considering the case when the transistor is about to switch to the active region, then Vbe=1.8V while Ve is still 0V, hence according to the previous formula<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cepsilon%20=%5Cfrac%7B1.8%7D%7BA%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cepsilon%20=%5Cfrac%7B1.8%7D%7BA%7D" title="\epsilon =\frac{1.8}{A}" /></a></div>
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Since the opamp has a very large gain A (about 200000 for ua741), this shows that ε is infinitesimal and very close to zero.<br />
The following plot shows the RPM vs voltage (Vin) curve for the improved Class B push pull amplifier design with opamp feedback as compared to the previous case<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgnLuTy_TAwp0Ai8nyl6dJPa57WUaY6IDJ2Rsrp5g3ixmXbCMQAT-tvLeBC_oOSbnBeYK5O43x7SA8jCMqVbcuVImKyEJqOdO6jYn1v4YYuA8qDaHUnBvbxWsDRVElTYxPwISxReCPgPw1/s1600/speed_vs_v2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="380" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhgnLuTy_TAwp0Ai8nyl6dJPa57WUaY6IDJ2Rsrp5g3ixmXbCMQAT-tvLeBC_oOSbnBeYK5O43x7SA8jCMqVbcuVImKyEJqOdO6jYn1v4YYuA8qDaHUnBvbxWsDRVElTYxPwISxReCPgPw1/s640/speed_vs_v2.png" width="640" /></a></div>
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We notice from the plot that the crossover distortion has been reduced from a value of 3.6 volts to a value of 0.5v with the improved feedback design. We know from the theory that the new crossover distortion is supposed to be infinitesimally small, however in practice, this turned out not to be true. The reason for this is unknown to me but most probably it has to do with the imperfections in the opamp. If you have an idea about the reason please don't hesitate to comment.<br />
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I do realize that this design might need improvements and maybe the implementation of a class AB amplifier would have provide a better response, however for my current analog control of a DC motor application the Class B push-pull amplifier turned out to be very useful as it provided an almost linear
relation between RPM and voltage. If you have any suggestions or improvements please comment on this post.<br />
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References and suggested readings:<br />
<ul>
<li>DC Motor and matlab analysis <a href="http://www.library.cmu.edu/ctms/ctms/examples/motor/motor.htm">http://www.library.cmu.edu/ctms/ctms/examples/motor/motor.htm</a> </li>
<li>DC motor's Hbridge and PWM drive <a href="http://modularcircuits.tantosonline.com/blog/">http://modularcircuits.tantosonline.com/blog/</a> </li>
<li>Audio class B push pull amplifier: <a href="http://www.allaboutcircuits.com/worksheets/bjtamp_b.html">http://www.allaboutcircuits.com/worksheets/bjtamp_b.html</a></li>
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<span id="goog_960152883"></span><span id="goog_960152884"></span></div>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com6Beirut, Lebanon33.879537013559244 35.4858398437533.035999013559241 34.22241234375 34.723075013559246 36.74926734375tag:blogger.com,1999:blog-1384219110719459434.post-49064593896600509022012-01-16T02:16:00.000+02:002012-04-09T02:39:57.358+03:00DIY smartphone headphone adapter (with MIC & control button)<div class="separator" style="clear: both; text-align: center;">
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRqas9vnbB_9Q7q4Dk9GtgdS0qy3IzxicMf2tD80EeHo1yqUPsLtUTot6kr34vP9QWEqn6hDC4z_cH49XMj8sioIvbr8VC-2K4a1J9ab1jtXg_XcYeoSdtm2yVKfLlXdspAof6Rr1_GGrT/s1600/p20120115-125543.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="207" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgRqas9vnbB_9Q7q4Dk9GtgdS0qy3IzxicMf2tD80EeHo1yqUPsLtUTot6kr34vP9QWEqn6hDC4z_cH49XMj8sioIvbr8VC-2K4a1J9ab1jtXg_XcYeoSdtm2yVKfLlXdspAof6Rr1_GGrT/s400/p20120115-125543.jpg" width="400" /></a></div>
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<ul>
<li>Do you happen to own a very expensive and personal set of headphones?</li>
<li>Do you have a special connection with your personal headphones such that you cannot listen to music without them?</li>
<li>Do you wish your personal headphones have the feature of the remote control (buttons) and MIC that smartphone earphones usually have? </li>
<li>Do you have an AUX line in your car's radio and you like to listen to your smartphone's music in your car?</li>
<li>Are you bothered when you receive a phone call while driving because you'll have to unhook your phone from the AUX input to answer, which can get you into an accident?</li>
<li>Are you like me and you prefer not paying tens of dollars for something that you can build yourself and will only cost you time (and a few dollars). There is nothing more rewarding then DIY! </li>
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<b>Ja3far </b>had the same problems mentioned above and in the video below he will show you the solution he came up with. (This is my first time shooting a DIY video, and I think I am a bad illustrator, so excuse my sloppy technique)<br />
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<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/WqXapYGLc0U" width="560"></iframe><br />
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In the video, <b>Ja3far </b>decided to make an adapter which he can hook up to his expensive headphones (or any other earphone/headphone). This connector has a microphone and a button. <b>Ja3far </b>can use the button to play/pause/move to the next track/answer phone calls (the features of the button depends really on the operating system of your smartphone). And the MIC is obviously used to communicate during a phone call without having to bother (very useful while driving). <br />
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This project requires little knowledge of electronics and soldering. You just need the following items:</div>
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1- Solder and Soldering Iron</div>
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2- Wires*</div>
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3- Electret MIC*</div>
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4- Push Button*</div>
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5- TRRS (Tip-Ring-Ring-Sleeve) audio Jack*</div>
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6- Multimeter (not necessary, but it is good to be able to perform continuity testing to follow the connections of the Jack)<br />
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*total cost is about 2$</div>
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All these items can be found at your local electronics shop.</div>
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The TRRS jack goes into the smartphone audio input, while it is important to note that regular earphones and headphones have a TRS type of jack as shown below:</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-ZMP9gHJ8Q2SQ5ZoBfPFAB8L8g8uiKaJGJgXCOLnr7DqsivuAktCo1SVZbok9rbFfw5km2lX6qrSQwveCrnljEQFBI88wZmWimKQniXVDsSDyDXuCJSTLo64qR_aMiLJ-baWyUHbZDCsw/s1600/20120112_230042.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><span style="font-size: x-small;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj-ZMP9gHJ8Q2SQ5ZoBfPFAB8L8g8uiKaJGJgXCOLnr7DqsivuAktCo1SVZbok9rbFfw5km2lX6qrSQwveCrnljEQFBI88wZmWimKQniXVDsSDyDXuCJSTLo64qR_aMiLJ-baWyUHbZDCsw/s320/20120112_230042.jpg" width="183" /></span></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">A TRRS audio jack</td></tr>
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUvJP3A2J3EbA66mP78S4xFW2EGcgJmYPPBU6g3F6opqtPkFqtcZlxGfSb83HTFq-c213Xh5o1nlFoqjoOgyJa8VoMatRJllGwQjVoubpRncPeZuYLlDyucLrWeu-IylT3jkyRtdOq6t3q/s1600/20120115_172804.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="168" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhUvJP3A2J3EbA66mP78S4xFW2EGcgJmYPPBU6g3F6opqtPkFqtcZlxGfSb83HTFq-c213Xh5o1nlFoqjoOgyJa8VoMatRJllGwQjVoubpRncPeZuYLlDyucLrWeu-IylT3jkyRtdOq6t3q/s320/20120115_172804.jpg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Headphones TRS jack</td></tr>
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For a headphone jack: TIP is connected to Left channel, RING is connected to the Right channel, and Sleeve is connected to the Ground.<br />
Oh and this is a final image of the adapter.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj_E1sHAxDdAN1JUxvOmPI-ai26QctZfdphWXmMCzPkI94mwqQ1T9xVSSv1uo65JeZPLtp2rjIwrWGWCKuOWywcyi02PNRehTv5G4TgyhBsZ0KdPTh34kx6Zxt-yZzyl4rEPNokBGev16z/s1600/20120113_004746.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj_E1sHAxDdAN1JUxvOmPI-ai26QctZfdphWXmMCzPkI94mwqQ1T9xVSSv1uo65JeZPLtp2rjIwrWGWCKuOWywcyi02PNRehTv5G4TgyhBsZ0KdPTh34kx6Zxt-yZzyl4rEPNokBGev16z/s320/20120113_004746.jpg" width="240" /></a></div>
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I know it doesn't look great but hey it does the job, and trust me wearing your headphones with this geeky looking gadget will definitely make you stand out.<br />
So I leave the aesthetics for the aesthetic minded.Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com6tag:blogger.com,1999:blog-1384219110719459434.post-39930759679660884222011-08-23T02:37:00.000+03:002011-08-23T21:41:58.554+03:00Chaos Theory: Simulating a double pendulum to understand how I owe my existence to Gaddafi's apple"<a href="http://www.amazon.com/Does-God-Play-Dice-Mathematics/dp/1557861064">Does God Play Dice? The New Mathematics of Chaos</a>" is a beautiful book by Ian Stewart. It provided me with a valuable introduction into the concept of chaos and chaos theory. Motivated by the book I decided to experiment with Chaos and write a dynamics simulator on MATLAB to simulate a 2 degrees of freedom pendulum (double pendulum).<br />
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In chaos theory 'Chaos' does not necessarily mean random (or a state of disorder). "Chaos occurs when a deterministic system behaves in an apparently random manner"<span class="Apple-style-span" style="font-family: Times, 'Times New Roman', serif; line-height: 18px;">. </span>Chaos is actually all around us. Chaos is the rule rather than the exception.<br />
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It is only when you think that everything is under 'control' that you wake up one morning to see that yesterday's weather forecast was all wrong and there is a huge storm outside, you check the stock market only to find out that you have lost thousands of dollars. HELL! you turn on the news only to realize that suddenly the Libyan people rose against a crazy tyrant who ruled them for 42 years. Chaos.<br />
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An important characteristic of Chaotic systems is their high sensitivity to initial conditions. Even for a deterministic system (with no random elements), this high sensitivity to initial conditions is what causes the impossibility of long term prediction of the system's behavior. A slight change in the initial conditions would yield completely different and diverging end results.<br />
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To experiment with Chaos, I wrote a dynamic simulation of a double pendulum (2DOF pendulum) on MATLAB. The double pendulum is a classical example of Chaos theory. I used the "Simple Forward Kinematics library for Robotic Chains" that I developed back in 2010 (<a href="http://www.mathworks.com/matlabcentral/fileexchange/31170-simple-forward-kinematics-library-for-robotic-chains">click here</a> to download), and I developed a new library to compute the joint-space dynamic equations and to perform the simulation for any kinematic chain (<a href="http://www.mathworks.com/matlabcentral/fileexchange/32638">click here</a> to download). So back to our chaos theory. To experiment, I ran two simulations:<br />
- The first (on the left in the video below) is a simulation with a base joint initial position of 130 degrees<br />
- The second (on the right in the video below) is a simulation with a base joint initial position of 129 degrees<br />
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<iframe allowfullscreen="" frameborder="0" height="345" src="http://www.youtube.com/embed/brs8l-Jzbl4" width="560"></iframe><br />
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Notice that although the initial conditions are almost the same, a difference in the trajectory begins to be noticeable only after 7 seconds. This difference increases as time passes. And after 40 seconds we notice that each pendulum is located on a totally different position in space.<br />
We've all heard of the vivid and beautiful term "the butterfly effect". Here it is. The impossibility of predicting the long term behavior of the pendulum.<br />
<br />
In 1972, Muammar Al-Gaddafi, while having diner in his tent and surrounded by his beautiful amazonian guards, decided to eat an apple rather than a banana. Imagine he ate the banana instead and it turned out the banana was contaminated with a deadly bacteria. He would have died after a month of suffering. Libya would have been 'inherited' by a crazier person (as is always the case). This person would have changed the entire political scene in the region, maybe causing the Lebanese civil war to be more intense. My father would have decided to flee the war and immigrate to Canada and he wouldn't have met my mother. I wouldn't have existed. I owe my existence to Gaddafi's apple.<br />
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MATLAB Files:<br />
-<a href="http://www.mathworks.com/matlabcentral/fileexchange/31170-simple-forward-kinematics-library-for-robotic-chains"> </a><a href="http://www.mathworks.com/matlabcentral/fileexchange/31170-simple-forward-kinematics-library-for-robotic-chains">Simple Forward Kinematics library for Robotic Chains</a><br />
- <a href="http://www.mathworks.com/matlabcentral/fileexchange/32638">Dynamics Simulator for Kinematic Chains</a>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com1tag:blogger.com,1999:blog-1384219110719459434.post-90321777499525509982011-08-04T03:13:00.000+03:002012-04-09T02:45:57.050+03:00Sound Triggered Flash: High speed photography<div class="separator" style="clear: both; text-align: center;">
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgA_5J0u9rCXwLl0Z8sWUdEHgT-vdwJILYXqBpBDFq05F8435g50vDmvPoWrbzVnUMnyvdZMUTUn6jkiROJ9Wc-zR6sbRDn0ItxF3Iytgi4gf9fxgnYH4GYsOZRtCiDEfomPSAGVrhm9-P4/s1600/balloon.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgA_5J0u9rCXwLl0Z8sWUdEHgT-vdwJILYXqBpBDFq05F8435g50vDmvPoWrbzVnUMnyvdZMUTUn6jkiROJ9Wc-zR6sbRDn0ItxF3Iytgi4gf9fxgnYH4GYsOZRtCiDEfomPSAGVrhm9-P4/s400/balloon.JPG" width="306" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">capturing scene invisible to the naked eyes: water balloon popping</td></tr>
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I was always amazed with Discovery Channel's <a href="http://www.youtube.com/watch?v=X0-TbUUXDtM">Time wrap</a> video clips. So I decided to do some experimenting on my own. A high frame rate video camera costs thousands of dollars... that was out of the question. A compromise needed to be made... instead of shooting videos, let's go for high speed photography. Sound Triggered Flash. As the name indicates, it is a flash triggered by a sound impulse. Using my SLR camera with the shutter open in a dark room, I would be able to capture photos of sound generating events.</div>
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Simple but inspiring. Enough to get me started on the project.<br />
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After doing some online search, I was able to find some links for DIY sound triggered flash. They were pretty helpful to get me started, however I decided to drop the research and just go with my own circuit design (more fun).<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglxfxCbXj3mSOfIvhBZ_sYGRyi9FLmAALy4GrnBlMdbTMia-WTBKERz3P_DdEYXoa0wqDOLhurUtcTm0dM-Mq4ewX8obmnWUeXpN7vpiqICDXwlSc9is4SneRFxZHTpU5mZJ5xyLth7bq5/s1600/DSC_1078.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="214" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglxfxCbXj3mSOfIvhBZ_sYGRyi9FLmAALy4GrnBlMdbTMia-WTBKERz3P_DdEYXoa0wqDOLhurUtcTm0dM-Mq4ewX8obmnWUeXpN7vpiqICDXwlSc9is4SneRFxZHTpU5mZJ5xyLth7bq5/s320/DSC_1078.jpg" width="320" /></a></div>
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<b><span class="Apple-style-span" style="font-size: large;">1. Component list:</span></b></div>
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- <a href="http://thefilmplace.com/assets/images/FunSaver_w_flash03.jpg">Disposable camera </a> with built-in flash x1<br />
- Electret Microphone x1<br />
- 9V battery x1<br />
- LM386- Low voltage audio power amplifier x1<br />
- LM339- Comparator x1<br />
- NE555- 555 timer x1<br />
- TIP120- BJT darlington transistor x1<br />
- 10Kohm potentiometer x2<br />
- Resistances: 10K x7 - 5K x 1 - 510 x 2<br />
- Capacitors: 10nF x3 - 10uF x2 - 220 uF x1<br />
- LED x2<br />
- On/Off dip switch x 2<br />
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<b><span class="Apple-style-span" style="font-size: large;">2. Hacking the disposable camera:</span></b><br />
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You must have realized by now that we only need the flash circuit from the disposable camera (of course any professional flash would do the job, but for $10 the disposable camera flash is good enough). After cracking open the Kodak disposable camera that I got, and analyzing the amazing ingenuity behind the trigger/shutter/flash mechanisms, i focused on the flash circuit.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDchS6tb9ta5PuM5OKl5MsRM_-Rkf3sS-TK6K-tGx8n6H2Wcsc_21iB8r0ccBethkb8jMVY4wWCrw0rkXQT_cgEvpn2-Yl5GZj1YuWo90_sV-3XsaxVf9aTJ-_1MjPTBkHtA7-eRhykG7y/s1600/Hacking_Disposable.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjDchS6tb9ta5PuM5OKl5MsRM_-Rkf3sS-TK6K-tGx8n6H2Wcsc_21iB8r0ccBethkb8jMVY4wWCrw0rkXQT_cgEvpn2-Yl5GZj1YuWo90_sV-3XsaxVf9aTJ-_1MjPTBkHtA7-eRhykG7y/s1600/Hacking_Disposable.jpg" /></a></div>
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Now notice how I carefully hold the flash circuit PCB. Notice how there is a 185uF - 330V capacitor in the circuit. I was actually electrocuted by the 330V capacitor -twice. Not fun. Not deadly, but not fun. (What doesn't kill you makes you stronger doesn't really apply in this case..)<br />
So I have to say this..<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNLoCCp9oAuDiRQZq_EvTs2M0HVIDFgb7OmR2YHr_Gy5AlGDVisIPbjB7-cpIvW38wbIr7S8pasAGOsdoTjiXdSX130f4-CLEvy3M13y5JtfX1Fi0rdW-NTcjEHaeI_vD_kn9kmp_iJ0Kb/s1600/capacitordischarge.jpg" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgNLoCCp9oAuDiRQZq_EvTs2M0HVIDFgb7OmR2YHr_Gy5AlGDVisIPbjB7-cpIvW38wbIr7S8pasAGOsdoTjiXdSX130f4-CLEvy3M13y5JtfX1Fi0rdW-NTcjEHaeI_vD_kn9kmp_iJ0Kb/s200/capacitordischarge.jpg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Courtesy of "<a href="http://electronics.howstuffworks.com/camera-flash3.htm">How camera flash work</a>" article</td></tr>
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<b>HAZARD: DON'T TOUCH THE CAPACITOR LEADS WITH UR BARE HANDS!! </b><br />
<b>Be careful in handling the flash PCB. It is preferable to discharge the capacitor by triggering the flash before holding the pcb.</b><br />
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</b><br />
As you can see, the flash circuit is powered with a 1.5V AA battery. It consists of impulsing a high voltage into a xenon tube. So the circuit boosts up the battery's low voltage into a high voltage to charge the 330V capacitor. More theoretical info can be found in this nice "<a href="http://electronics.howstuffworks.com/camera-flash3.htm">How camera flash work</a>" article.<br />
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After understanding the circuit, I realized that connecting the two metallic leads M1 and M2 in the above picture causes the flash to trigger. PERFECT! (The circuit differs between different brands, however you will always find the similar two metallic leads). Again DON'T CONNECT THE LEADS WITH YOUR BARE HANDS! I soldered two wires to M1 and M2 as can be seen in the picture below.<br />
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<a href="http://electronics.howstuffworks.com/camera-flash3.htm"><img border="0" height="214" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEimnySQmugTMzwMKXFJyWdBZNt8w7kq-O8GpEw-v-SDjZCgyjPA9E0wfHm66JC4F-OFbZl5oYnq9MmbPoFDbd7OBmTTc8mkcvR_lfrNn1MU19aw6QeGs0-aWoB54fCDYGd-pLAo3pMahOOq/s320/DSC_1063.jpg" width="320" /></a></div>
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<b><span class="Apple-style-span" style="font-size: large;">3. The electronics:</span></b></div>
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First step in designing my circuit was to decide on the user interface. I would like the user to:</div>
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-Tweak the sound sensitivity using a potentiometer</div>
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-Tweak the time delay in the order of milliseconds between the sound detection and flash triggering using a potentiometer. (I realized during experimentation the need for this feature, else the pictures were captured a bit too early)</div>
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-Test the sound detection using a LED.</div>
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-Press a push button to switch the circuit from triggering a LED into triggering the flash.</div>
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I prefer not using a microcontroller for such a simple circuit, it would be an overkill. Let's do it the old challenging way: build my own A/D conversion and triggering.</div>
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The idea behind the circuit is simple: </div>
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<ol>
<li>Pick up the signal using an Electret microphone.</li>
<li>Amplify the signal using LM386.</li>
<li>Compare the amplified signal to a constant threshold (which can be modified using a pot to change sensitivity) using the LM339 comparator.</li>
<li>The comparator's falling edge would trigger a pulse using the 555 timer in Monostable mode.</li>
<li>The pulse would be delayed by charging an RC circuit connected to the LM339 comparator. (The resistance of the RC is actually a pot so that that we could vary the value of the time delay)</li>
<li>The delayed pulse coming out of the comparator would go into the base of the TIP120 transistor switch that would trigger the flash.</li>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAwUmCDPY2qMctOOnCLWUFbch_-6ai4yuhVh0eZYLGFSKzzuTOhQg7-pnZygWOVOvX9Y_T3uz0Z-cadjjUWURu63T6ezEnw0DiMpwj2FJl9X0TjKwuUDTDmRQpB1_BumOMEE3NubjuYhbN/s1600/schematic.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="330" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgAwUmCDPY2qMctOOnCLWUFbch_-6ai4yuhVh0eZYLGFSKzzuTOhQg7-pnZygWOVOvX9Y_T3uz0Z-cadjjUWURu63T6ezEnw0DiMpwj2FJl9X0TjKwuUDTDmRQpB1_BumOMEE3NubjuYhbN/s400/schematic.png" width="400" /></a></div>
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<b>M1 and M2 wires are connected to the H1-camera header in the schematic.</b></div>
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<b>Audio: </b>C1 - removes the DC component in the signal</div>
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C2 - removes the high frequency noise</div>
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LM386- amplifies the signal. C3 is connected between terminals 1 and 8 so that the gain is 200 (46db)</div>
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<b>Comparator: </b>Pot1-varies the voltage between 4.5V and 9V at the positive terminal of the LM339 comparator (because the output of the amplifier is biased at 4.5V)</div>
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When the signal voltage goes above the voltage specified by Pot1, a falling edge occurs that would trigger the 555 timer to generate a pulse.</div>
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<b>555 timer</b> is in Monostable mode: the pulse width is t=R4*C4*ln(3)=2.4 sec.</div>
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<b>Time delay: </b>The pulse generated by the 555 timer will charge the RC circuit composed of pot2 and C6.</div>
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The RC is a first order system:</div>
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<a href="http://www.codecogs.com/eqnedit.php?latex=%5Cfrac%7BV_%7Bout%7D%7D%7BV_%7Bin%7D%7D=1-e%5E%7B-t/%5Ctau%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?%5Cfrac%7BV_%7Bout%7D%7D%7BV_%7Bin%7D%7D=1-e%5E%7B-t/%5Ctau%7D" title="\frac{V_{out}}{V_{in}}=1-e^{-t/\tau}" /></a></div>
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which is compared using LM339 to a voltage divider circuit providing 10k/15k*Vin. As soon as this voltage is reached, the flash would trigger. The time delay equation is:<br />
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<a href="http://www.codecogs.com/eqnedit.php?latex=10/15&=&1-e%5E%7B-t/%5Ctau%7D%5C%5C%20t&=&%5Cln%280.333%29%5Ctau%5C%5C%20t&=&-1.0996e%5E%7B-5%7DR_%7Bpot2%7D" style="margin-left: 1em; margin-right: 1em;" target="_blank"><img src="http://latex.codecogs.com/gif.latex?10/15&=&1-e%5E%7B-t/%5Ctau%7D%5C%5C%20t&=&%5Cln%280.333%29%5Ctau%5C%5C%20t&=&-1.0996e%5E%7B-5%7DR_%7Bpot2%7D" title="10/15&=&1-e^{-t/\tau}\\ t&=&\ln(0.333)\tau\\ t&=&-1.0996e^{-5}R_{pot2}" /></a></div>
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So the maximum time delay achieved with the 10K pot is t =110ms.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBFzO95xL-oJDj3RFrKXQpxq4jEhheJ6CO_erC_7GYhyphenhyphenWYVhUuXW6NKXmUbmuroRQMNlObFbtzWM9QGHVEaqzAEsKEjtH5xzzBtDXYAOTwJNoQh5JGCegacp6cSt2B68u-UcBkdXQw_TM7/s1600/timedelay.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="300" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiBFzO95xL-oJDj3RFrKXQpxq4jEhheJ6CO_erC_7GYhyphenhyphenWYVhUuXW6NKXmUbmuroRQMNlObFbtzWM9QGHVEaqzAEsKEjtH5xzzBtDXYAOTwJNoQh5JGCegacp6cSt2B68u-UcBkdXQw_TM7/s400/timedelay.png" width="400" /></a></div>
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<b>Trigger: </b>Finally, the signal switches the TIP120 transistor. If SW2 is pressed, LED2 would light up (for testing purposes), otherwise the flash would trigger.</div>
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<b><span class="Apple-style-span" style="font-size: large;">4. Prototype and PCB</span></b><br />
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One of the earliest models I made was based on the NE5532 audio amplifier. Here are a few images of the early prototype built with a perforated board.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKkjieHzlgIFfa-3qPej4E3x2qC0U2wyCeUXH4FtI7DTiVJGoD2Ej4Tm9AYcAQsb8-LInRClJHtWBRXOZFgPP6A6behuFpIUJInanxM35fgjEhgghZMiWdSOzRLSJ3rOi3kMQgvNqbC-Wd/s1600/prototype.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="157" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiKkjieHzlgIFfa-3qPej4E3x2qC0U2wyCeUXH4FtI7DTiVJGoD2Ej4Tm9AYcAQsb8-LInRClJHtWBRXOZFgPP6A6behuFpIUJInanxM35fgjEhgghZMiWdSOzRLSJ3rOi3kMQgvNqbC-Wd/s320/prototype.jpg" width="320" /></a></div>
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The reason I switched to LM386 amplifier is for its simplicity, however NE5532 provided the option of having a pot in order to modify the gain.<br />
I designed a single sided Printed Circuit Board of the new circuit<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFY3xhjpCKpUt6vUPEAhNYXJDSleaaZTs_wRP2D5cVtXHGfSKJYs4xD0B4JWh8kwU2VNd-y1kYX9AYYdzhnzgFowczfOKaLUU8GSEyK2b4MBm4boiv7CCNmt3vxx1rtMY5u1yw0cvHOEKK/s1600/pcb.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="177" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiFY3xhjpCKpUt6vUPEAhNYXJDSleaaZTs_wRP2D5cVtXHGfSKJYs4xD0B4JWh8kwU2VNd-y1kYX9AYYdzhnzgFowczfOKaLUU8GSEyK2b4MBm4boiv7CCNmt3vxx1rtMY5u1yw0cvHOEKK/s320/pcb.png" width="320" /></a></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZKpGKqDcFvK6hYUZ1EXe1Wd6lwKy7Q7sESTS475BJfAIfl9dOi8z85BlQ-KSycE9fkIm377wfw9jcc3l4ykGcofgvTNuJevw83eTBA2MLlb0vkKHT1cs4LXH4ipRnBulcUbfe1GNlpKPb/s1600/pcb_assembled.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgZKpGKqDcFvK6hYUZ1EXe1Wd6lwKy7Q7sESTS475BJfAIfl9dOi8z85BlQ-KSycE9fkIm377wfw9jcc3l4ykGcofgvTNuJevw83eTBA2MLlb0vkKHT1cs4LXH4ipRnBulcUbfe1GNlpKPb/s320/pcb_assembled.jpg" width="317" /></a></div>
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<a href="http://dl.dropbox.com/u/4924768/SoundTriggeredFlash_GerberFiles.zip">Click here</a> to download Gerber files of the PCB.<br />
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<b><span class="Apple-style-span" style="font-size: large;">5. Experimentation:</span></b><br />
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Here are a some of early pictures I took:<br />
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<b> </b><br />
<table style="width: 194px;"><tbody>
<tr><td align="center" style="background: url(https://picasaweb.google.com/s/c/transparent_album_background.gif) no-repeat left; height: 194px;"><a href="https://picasaweb.google.com/113000065480657015081/SoundTriggeredFlash?authuser=0&authkey=Gv1sRgCMv8we3JjMmnGA&feat=embedwebsite"><img height="160" src="https://lh5.googleusercontent.com/-9M6RLeJaB1I/TjvGC0F3JOE/AAAAAAAAAOs/ExZuStizhL8/s160-c/SoundTriggeredFlash.jpg" style="margin-bottom: 0px; margin-left: 4px; margin-right: 0px; margin-top: 1px;" width="160" /></a></td></tr>
<tr><td style="font-family: arial,sans-serif; font-size: 11px; text-align: center;"><a href="https://picasaweb.google.com/113000065480657015081/SoundTriggeredFlash?authuser=0&authkey=Gv1sRgCMv8we3JjMmnGA&feat=embedwebsite" style="color: #4d4d4d; font-weight: bold; text-decoration: none;">Sound triggered flash</a></td></tr>
</tbody></table>
</div>
<div>
<b><span class="Apple-style-span" style="font-weight: normal;">More experimentation pictures will be uploaded soon.. stay tuned.</span></b><br />
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</b><br />
<b><span class="Apple-style-span" style="font-size: large;">6. Purchase</span></b></div>
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Contact us at <a href="http://www.depotbeirut.com/">DepotBeirut</a> if you'd like to purchase a PCB or even a fully assembled sound triggered flash.<br />
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Cheers,</div>
<div>
<br />
<br /></div>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com3tag:blogger.com,1999:blog-1384219110719459434.post-82426479781152234812011-07-22T02:55:00.000+03:002012-04-09T02:43:08.445+03:00Lebanese electronics shops: the TSOP experience.<br /><div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiR0U_-aMr-9t2qXa4M9PkLZzVEeA1HdsZFsBoR9YyaEez_gP0p0Nl2H00LCTwljnwfsvWukWeD9TbTYuxH5ipJvAK8q5F0T00TVDTk7tQ9kcLxZILOg0bsyy2WuDZpt4aGPymTAMneHiPp/s1600/critic.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiR0U_-aMr-9t2qXa4M9PkLZzVEeA1HdsZFsBoR9YyaEez_gP0p0Nl2H00LCTwljnwfsvWukWeD9TbTYuxH5ipJvAK8q5F0T00TVDTk7tQ9kcLxZILOg0bsyy2WuDZpt4aGPymTAMneHiPp/s320/critic.jpg" width="320" /></a></div>
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As everybody working with electronics in Beirut would agree. We don't have a great accessibility for components and IC's. If I am dealing with non common components, I don't even bother looking around in the local electronics hardware shops that we have (Katranji, Incotel, Boujikian, Narinco, etc.) I wait till I gather a big list and I order my components from abroad (that is an extra 50-100$ added to the bill).<br />
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I will not talk about shipping in this post, however I will be talking about the wonderful experience one has to deal with in our lovely local electronics shops.<br />
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Starting with Boujikian, all I can provide you is a simple advice: if you have an Armenian friend, tag him along with you.<br />
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Now I would like to share a nice story. A few weeks ago I was building an IR remote control emitter/receiver circuit (I will provide info for the circuit in another post). So I needed to buy an IR receiver chip TSOP1738 that only works with carrier frequency of 38KHz. Perfect.<br />
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First thing: Check <a href="http://www.ekt2.com/">Katranji's</a> website if they have the component. (+3points to katranji for having a website) However the website search engine sucks, so you have to look manually for the part (-1pt). After not finding the part on their website. You would grab your component name/number and head to Jneh in the middle of the traffic jam and heat. Once you get there, don't expect to be treated well. Sometimes don't expect to be treated at all. (-1pt). I was lucky enough to find a decent help, lets call him Nabil (hypothetical name for a hypothetical person)<br />
-Bassam: Can I have the following component please.<br />
Nabil stares at his monitor for 5 minutes only to tell me that they don't have it.<br />
-Bassam: Do you have anything equivalent. TSOP18...21.. wlek 28... anything at all...<br />
Nabil stares at his monitor again 5 minutes only to tell me that they don't have.<br />
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-Bassam: But sometimes my friends come to get some phototransistors, and you either end up giving them photodiodes or TSOP chips (true story), so I am sure you have something equivalent.</div>
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Nabil goes backstage for 5 min and comes back with a TSOP looking chip (not TSOP thou).</div>
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-Bassam: Ok great so what is the name/number of this chip? </div>
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Nabil stares at his monitor for 5 minutes only to tell me that they don't know.</div>
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-Bassam: Tayeb, what is the carrier frequency for this chip.. anything.. just give me any info.</div>
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Needless to say, Nabil didn't know.</div>
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I ended up going back to my workshop and spending 2 hrs trying to figure out pointlessly how to make the chip work. So this leaves Katranji with 1 point in my improvised grading scheme. <br />
Don't get me wrong, i have a complicated love/hate relationship with Katranji & Nabil that only the people knowledgeable in electronics in Lebanon would understand, but you have to admit Katranji does have a wide and good range of components available. And most of the time, if you were instructive and knew what you want, you will end up finding at Katranji's.</div>
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Getting frustrated. I called Incotel. The guy was really friendly. and as soon as I told him I need a TSOP1738, he told me that they don't have it but they have something equivalent. I couldn't believe it. His voice was like a divine melody in my ear. I went to Incotel, got the needed chip. The guy even suggested a IR led that works on the same wavelength as my chip. Perfect +10pts for Incotel for their great customer support. </div>
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So I bought 4 TSOPs and 4 LEDs and was about to leave when I asked for the bill. Ok. -8pts for Incotel. I won't tell you the price so that you won't get depressed. But I can say that it was the expected price x4!!</div>
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This leaves Incotel with 2pts on my improvised grading scheme.</div>
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Incotel 2pts vs. Katranji 1pt</div>
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Well if you don't care about price. Go to Incotel... but honestly you'd be better off gathering a big component list and ordering from abroad. </div>
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N.B. I will be criticizing other electronics shops as I write in my blog. And I will be elaborating more on my love/hate relationship with Katranji and Nabil.</div>
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<br /></div>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com1tag:blogger.com,1999:blog-1384219110719459434.post-34892520530829054742011-07-19T03:04:00.000+03:002012-04-09T02:41:50.987+03:00Mr. Warhol here is my chance...15 minutes of fame can also be life changing.<span class="Apple-style-span" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></span><br />
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<span class="Apple-style-span" style="font-family: inherit;">Back in 2008, I attended a presentation about a freshly starting pan arab competition: </span><a href="http://www.starsofscience.com/" style="font-family: inherit;">Stars of Science</a><span class="Apple-style-span" style="font-family: inherit;">. It </span>immediately<span class="Apple-style-span" style="font-family: inherit;"> got my attention. The concept of the competition is simple. You have an idea for a product or an innovation of some sort, you present it, if it gets accepted you go to Qatar and develop it with the help of experts. </span></div>
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<span class="Apple-style-span" style="font-family: inherit;">It all sounds perfect and nice.. oh wait... there is something missing... it is a reality TV show!! You actually have to work all day, all week, for months in a workshop full of cameras, microphones, and its going to be broadcasted all over the Arab world. Everybody will be observing every step you take, every mistake you make. Euh.. scary? but this must be something new in my life. Once in a lifetime opportunity to try something new. why not? let's apply.<br />
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<span class="Apple-style-span" style="font-family: inherit;">Mr. Warhol here is my chance.</span><br />
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<span class="Apple-style-span" style="font-family: inherit;">So what about <a href="http://www.starsofscience.com/">Stars of Science</a>? a brief description: <br />
</span><span class="Apple-style-span" style="font-family: inherit;">Stars of Science, initiated by Qatar Foundation in 2009, is the first Pan-Arab reality-TV program dedicated to innovation, aiming to shine a spotlight on the next generation of young Arab innovators. Following an international recruitment campaign among more than 5000 people, 16 young women and men of Arab origin, from different academic and professional backgrounds, are selected by a Pan Arab jury and given the chance to develop their own innovation project. The selected candidates are invited to enter a specially-designed workshop, located in Doha, where they have access to an array of state-of-the art resources as well as the support of top professionals. The 16 take part of a competition in successive rounds, each of them corresponding to a key stage of the innovation process (proof-of-concept, engineering, design, business and marketing). </span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh72rNiHiwDB71zLTHEN15Tf3IqKvVi1DoaOm9aHkOH7uwp6RmH5D3npx8aDjQTy4EgwlFzT5dVhlLwXYm05ycF7zrA5Omo3SaxT__Ku4h6zIj_eOIPnkH3qEcRfSG-upLgVFPcbKuM-xk1/s1600/img2.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="216" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh72rNiHiwDB71zLTHEN15Tf3IqKvVi1DoaOm9aHkOH7uwp6RmH5D3npx8aDjQTy4EgwlFzT5dVhlLwXYm05ycF7zrA5Omo3SaxT__Ku4h6zIj_eOIPnkH3qEcRfSG-upLgVFPcbKuM-xk1/s320/img2.png" width="320" /></a></div>
In 2009, I applied and I was selected for my product- an automated tuner device for all string instruments that I called Dozan (stay tuned as later I will have a post dedicated for Dozan from early stage till now). After successfully passing all the stages I won the 1st prize in the competition.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh734E0-m_7vJwVHg70Pc3sXVSfCTBv3-W9I2wqziXpJ5WgUQuo5weX_3uSVvlUfrh1-xwuwvGoqt35w9fVzxPWR-XWLXwoVUqHhW4CHhRIXU89oO5f80-k5_1iV79WRTTwgBAksnSjy7cd/s1600/img1.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="218" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh734E0-m_7vJwVHg70Pc3sXVSfCTBv3-W9I2wqziXpJ5WgUQuo5weX_3uSVvlUfrh1-xwuwvGoqt35w9fVzxPWR-XWLXwoVUqHhW4CHhRIXU89oO5f80-k5_1iV79WRTTwgBAksnSjy7cd/s320/img1.png" width="320" /></a></div>
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Mr. Warhol, here comes the 15 minutes. <br />
The media buzz was intense here are a few articles: <a href="http://www.dailystar.com.lb/News/Local-News/Jul/01/Lebanese-engineer-wins-science-competition-in-Qatar.ashx#axzz1SHPYPKTz">dailystar</a>, <a href="http://en.news.maktoob.com/20090000006341/ArticleAnnouncement.htm">maktoob</a>, (if you google you will find plenty of international magazines and blogs also). I was even announced one of the <a href="http://www.arabianbusiness.com/30-under-30-151844.html?view=profile&itemid=151858">30-under-30</a> of the Arab world’s best and brightest entrepreneurs by <a href="http://arabianbusiness.com/">ArabianBusiness.com</a><span class="Apple-style-span" style="font-family: inherit; line-height: 100%;"><span class="Apple-style-span" style="color: #333333; line-height: 17px;">.</span></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJRVHCS5pA954muH50W3QSNQBjmUGnwLFQAccggBf0UcaYB85iqABbTQO5D2kFcS8r4ahplfQl5qcHCRbdnVlu9B6FKLw1e087dFh90L5OA1OD62odcjnF91HKvQdqAMrg6zaHiFI_bj-3/s1600/Screen+shot+2011-07-19+at+5.10.23+AM.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="224" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgJRVHCS5pA954muH50W3QSNQBjmUGnwLFQAccggBf0UcaYB85iqABbTQO5D2kFcS8r4ahplfQl5qcHCRbdnVlu9B6FKLw1e087dFh90L5OA1OD62odcjnF91HKvQdqAMrg6zaHiFI_bj-3/s320/Screen+shot+2011-07-19+at+5.10.23+AM.png" width="320" /></a></div>
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Wow, ok, great. now what? Honestly, a part of me enjoyed the 15 minutes but a bigger part wanted them to be over because i knew that this is when the real work starts. Reality hits. WORK work WORK! I want to finish my masters, my research and I want to develop Dozan and make it a success story and share my experience with fellow local entrepreneurs and innovators going on the same path. Oh and I would like to have a hand in changing the arab world from a consumer to a producer of technology. too much to ask for? step by step.<br />
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<span class="Apple-style-span" style="color: #333333; line-height: 17px;"><span class="Apple-style-span" style="font-family: inherit;">Mr. Warhol, I had my chance and I would like to tell you that even though the 15 minutes can be over, but they can also be life changing.</span></span><br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEfLCUhrxlOEtP-sNjjCvhXMxVqyrUx-Ph6lOoIN4jF5H5QsV4axx9OY9W_Fa_-qUSujVJ0YDdtLZWo7EltUaptKl1t7EEW6YGD6RVmONFoSFiXOuTMEd81Oc167XRf8VuhapevEs0V2g7/s1600/n727286080_3292256_5622453.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgEfLCUhrxlOEtP-sNjjCvhXMxVqyrUx-Ph6lOoIN4jF5H5QsV4axx9OY9W_Fa_-qUSujVJ0YDdtLZWo7EltUaptKl1t7EEW6YGD6RVmONFoSFiXOuTMEd81Oc167XRf8VuhapevEs0V2g7/s200/n727286080_3292256_5622453.jpg" width="158" /></a></div>
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<span class="Apple-style-span" style="font-family: inherit;"><span class="Apple-style-span" style="color: #333333; line-height: 17px;">p.s. to all the young innovators in the arab world reading this, go to </span><span class="Apple-style-span" style="line-height: normal;"><a href="http://www.starsofscience.com/">Stars of Science</a> and apply for the coming seasons!</span></span></div>
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</div>Bassam Jalghahttp://www.blogger.com/profile/10082259174059952882noreply@blogger.com0