Scioly.org

My arm is a master-slave system, and as far as human control I think it is probably the best option. Though it can be rather tricky to get the hang of and requires more practice.

As far as preprogramming an arm to do everything, it's just a balance of risk and benefits. Programming the arm can and will certainly make it easier to get a perfect score in the time limit, but at the same time, if something goes wrong, or something moves just a small amount, the entire run could be ruined and your score could actually be very very low. So it's a risk, and as with everything in life, the question is just how much risk are you willing to take?
Just my 2 cents

Edit: Very nice master-slave arm, http://www.youtube.com/watch?v=58DIp7NblzU

iwonder wrote:I don't quite grasp how you can do a master/slave system without some form of a microcontroller... If you use rc hobby servos you need one to generate the PWM to drive to servos, and if you had straight gearmotors you would need position feedback from both arms and a processor to run the control loop to position the arm... is there something simple I'm missing?

Having integrated circuits is not the same thing as having a full fledged microprocessor. You are correct that you generally need some sort of signal conditioning, but that can be done with discrete components instead of a complete computer. For example, a quick google search for "circuit servo motor" comes up with lots of results, including this simple design, which requires only a 555 timer and some resistors / caps: http://www.epanorama.net/circuits/servo10v.html

Neat design... Personally an arduino or equivalent seems simpler, but that would definitely work.

In regards to a Master slave system, is there an estimated cost to build a quality arm?

questionguy wrote:In regards to a Master slave system, is there an estimated cost to build a quality arm?

This is assuming you know how to wire the stuff together, but a low-end estimate off the top of my head would be:
~40 dollars for motors (8 dollars/servo for 5 servos)
~20 dollars for an Arduino Uno (a mega would be better for the extra ports, but those are ~60. If you're smart about it you should be able to get away with an Uno)
~5 dollars for 5 potentiometers
~25 dollars for batteries/assorted wires/electronic components (resistors, whatever else small stuff you might need.)
- 10 dollars for wood/metal/plastic/whatever for the frame

Total: 100 dollars. I actually think you could build a robot arm for less than that if you are experience with electronics, but the arduino/potentiometer combo makes things relatively easy for most people as long as you are willing to experiment a bit.

Out of curiosity, what are people building thier frames out of? I have yet to find a good set up which is the right size, but not too heavy and cumbersome.

twototwenty wrote:Out of curiosity, what are people building thier frames out of? I have yet to find a good set up which is the right size, but not too heavy and cumbersome.

Carbon-Fiber FTW

Really? How much did that amount of carbon fiber cost you?

$36 for a 3/4 inch carbon pultruded tube, 48 inches should do you. From a REAL quick search.

Jeff Anderson
Livonia, MI

I got 1"x12" pieces for about $5 each