Moving some joints, thank goodness they still work

A project log for RobotResto: Restoring a 4 Axis Arm

Using new technology to bring an old 4 axis DC robotic arm back to life

reiner-schmidtreiner schmidt 06/11/2016 at 00:251 Comment

A Friday evening isn't always the best time to throw a little extra working into resorting this old robot but I couldn't wait to see it move so I had to spend a couple hours messing around with it before signing off for the weekend.

To design a new controller we need to know something about the motors. At the moment all we know is that they are 12V and DC, other than that there is no information. Really all I need to build the controller now is the output of the potentiometers and the current usage of the motors. I suspect that it will be less than an amp each, the motors arnt that big.

To test the motors I am going to power them manually and run the power through a Fluke meter and record the max current. The max current with a stalled joint was about 500mA, so it looks like the motor driving is a job for a DRV8801 chip!

Testing the potentiometers shows that they are continuous rotation pots (cool), and have a range of 0 - 300 Ohms. The next step is going to be creating a method of connection for potentiometer/encoders.


Thomas wrote 12/17/2017 at 15:36 point

Are the pots of the "conductive plastics" type? Performance is best if the wiper current stays well below 10µA. I recommend using an op-amp, or a very high impedance ADC input of a µC .

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