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Topic: Controlling industrial servo/tachometer feedback (Read 2631 times) previous topic - next topic

MaxThomas

I'm attempting to build a controller for an existing pan/tilt camera head that uses continuous servos (schematic/spec sheet attached) with DC (analog) tachometer feedback. I've been researching ways to do this, and was hoping to get some advice on the plan so far...

Some of the specs on the attached sheet are cut off, but the motor is rated at ~6V/KRPM and ~7.68oz-in/A. I'll need to drive the motors at 18V (~3000RPM max.) at a current of around 3A average/7A peak per motor. Also, the spec sheet lists both Encoder and Tachometer specs, but ours have only the tachometer (wired similarly to Figure 2) which is listed as generating ~14V/KRPM.

Will it be possible to control these with a controller like the Pololu Simple Motor Controller? This doesn't offer an internal feedback system, but I'm thinking if the Arduino can get a speed from the Tachometer (I assume through some kind of voltage regulator to bring the ~42V@3000RPM down to a range it can handle) then I can compare the tach reading to where I want it to be and adjust the speed as needed.

Or, am I better off getting a controller that supports tachometer feedback internally, so the speed correction is done automatically?

The goal initially is real-time joystick pan/tilt control, but I'd like to expand that to repeatable motion-controlled moves afterwards. I understand I'll need a separate calibration system to get absolute positioning for that.

Does it seem feasible to control these motors this way, or are there other factors I'm not considering?

Thanks,
Max

fliggygeek

It looks like an interesting project, So long as the board can tolerate the power options, you can certainly make voltage dividers to reduce the voltage to a more acceptable level as the arduino doesn't use much current to take a reading. The tacho/encoder readings are very similar to part of a project I just finished, so you will be able to use those for motor feedback. You may want to look into PID feedback. I'd link the wiki article but im too tired, maybe another day. I'm here to answer any questions there too.

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