Buy an Axon, Axon II, or Axon Mote and build a great robot, while helping to support SoR.
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maybe something like this? http://www.sparkfun.com/commerce/product_info.php?products_id=9074
Your current project is the next one on my list!Rather than worrying about rotary pots, I am going to use flex sensors from Sparkfun: LinkIf you can afford them, they work great. Although be very careful with them, as they are rather fragile at their connection points (which btw are breadboard friendly).Follow step 4 of THIS Instructable on how to setup (and protect) the flex sensors. If your not comfortable with soldering directly on the connections of the sensor (like me), I found that they fit nicely tightly in between these Ic sockets.I would suggest the use of these flex sensors at the elbow, one or two at the wrist, and perhaps one for a claw (just one sensor attached to thumb or middle finger). Or if your rich, or just insanely determined on building a kickass robotic arm, maybe even a flex sensor for control over each individual finger...Now the shoulder joint movement along the pitch axis would be a tricky thing to measure with a flex or rotary potentiometer, so I'm planning on mounting an accelerometer (or gyro, if i can find a cheap Wii Motion Plus somewhere) on my lower tricep, near my elbow, and just measuring the angle.
Also, since your entire arm might stay stationary in relation to your body but move in relation to the ground, an accelerometer will give inaccurate readings - unless you give it another reference point, or have another accelerometer mounted elsewhere on the arm which would tell the microcontroller what the 'neutral' position is.
Your absolutely correct. And if you want to build a robotic arm that mimics arm position in relation to the body via two accelerometers, that would be perfectly fine. Its really all personal preference. Theres pros and cons for both methods -1. robot arm position relative to the ground or 2. robot arm position relative to your body.Why not try incorporating BOTH methods, and being able to switch between the two? Better yet, try adding a third alternative where you use a potentiometer to mimic the angle that would otherwise be measured by the accelerometer mounted on the body. That way you could possibly be lying on your back, while your microcontroller will think you are upright.
e.g. -Say you hold the Wiimote at arms length, [snip explanation]The movement will thus not be accurate, as the reference point for the sensor is the ground, not the upper arm. Thus, it will not measure angle to the upper arm, but to the ground.