Part of my PhD research at NYU-Poly involves predicting energy consumption in robotic systems, so I needed a robotic system to work with as a research platform to validate results.  So I convinced my group mates in my Mechatronics class in the Fall of 2011 that we should build a robotic arm.  I also wanted to use it as a project to learn motor control.  I had some high torque servo motors lying around from another project, but the control boards had been fried.  Since a servo motor is just a DC motor, some gears, and an integrated potentiometer, I could still use those if just the control board was fried.  So, I unscrewed the bottom cover, and used some desoldering braid to suck up the solder around the two motor terminals.

Then I was able to pull off the PCB.  However, the 3 wires from the potentiometer were still attached, so I cut those and ended up with something that looked like this:

I had also seen this post on Instructables by Chris Anderson on adding some potentiometers to a toy robotic arm to enable closed loop control.  Since I decided to work with these hacked servos, my potentiometers were already integrated, so I was set.  I want to share the process with you so you can start a little higher on the learning curve than I did.

By building a robotic arm, students will acquire assembly skills and be able to implement basic forward and inverse kinematics in simple Arduino code.

Step 1: Collect the parts - hardware

All of the parts for the arm itself were from Lynxmotion.com:

Part #    Name     Quantity     $total

HUB-08  Aluminum Tubing Connector Hub (pair)  2   $16.00
AT-04  Aluminum Tubing - 6.0"  2  $7.20
ASB-09  Aluminum "C" Servo Bracket with Ball Bearings Two Pack  1  $12.90
ASB-10  Aluminum Long "C" Servo Bracket with Ball Bearings Two Pack  1  $12.90
ASB-04  Aluminum Multi-Purpose Servo Bracket Two Pack  1  $11.95

Total: $60.95

You'll also want a base of wood or metal to screw the first servo motor and bracket down to. I found a scrap piece of aluminum u-channel in the basement machine shop at my school, but a 2x4 would work just as well.
<p>Hey <a href="http://www.instructables.com/member/dustynrobots/" rel="nofollow">dustynrobots</a>, I was curious of what material you used for the arms? It looks like thin aluminum pipe? I have to complete a similar project for school. Let me know. Thanks! :) Btw great video, I found the link below. </p>
Cool instructable
I was working through this and got a bit confused with the definitions of the variables since I took kinematics a while ago. This is a diagram for the forward kinematics part attached.<br> <br>
Cool instructable, I was a disaster in my Control Systems class (20+years ago) so this is particularly interesting as a practical teaching tool.
This needs a video. I was so looking forward to the video that I thought would be on the last page, and I was sorely disappointed.
Here you go! I'll embed this in the 'ible too <br>http://www.flickr.com/photos/dustynrobots/6531894535/in/set-72157629849425652

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Bio: I'm an enginerd, author, and teacher.
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