DC Servomotor drive for step / direction

[cswiger]

Just thought I'd share this creation for any other DIY'ers - did not find out there was a commercial equivalent product (but suspected there must be like the Gecko g201x - but last year I needed to convert step / direction signals from a grbl board to drive a couple of servo motors - one a nice z-axis servo found on ebay. Anyway, so I made my own from an arduino and a motor driver, using an encoder library, pid loop library, motor driver and timer libraries.

Code is free shared here for any interested parties: https://github.com/cswiger/dcservodrive

It'll never replace a Gecko - In fact I'll probably replace my mess with a g201x next time I get some funds

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[jeffserv]

Show some pictures of your mess, as you call it... that would be interesting.

As well, I get customers, who come in several times a year, with new ideas; and 9 times out of 10... it has already been built, and a little research on Google can reveal this now days.

I had one guy, who came in, with weekly meetings, for me to invent this great new way to dispense ink on a printing presses. He paid me for each meeting... and the 5th meeting... I order one sample, from Atlanta, GA and had it on my desk...

He nearly freaked out... he thought I had made it!!!! NO, I had just ordered an example. It was invented 5 years earlier, in Europe.

Good luck...

[awerby]

The Gecko 201X is a stepper drive, but they also make the G320X for brushed DC servo motors. I've had good luck with it, so if you decide to replace your "mess" and your motors have brushes, that would probably save you the cost of replacing them.

[cswiger]

Ok, here's pix - yes, I meant the Gecko g320x servo drive. This is the sweet z-axis I found on ebay for not a lot, why I need the servo drive:



This is the stock arduino mega2560 (can use an inexpensive Uno for just the one axis) and a sparkfun Ardumoto. The rest is a simple matter of programming:



The messy problem I'm wrestling with now is noise from the dremal / extension triggering false interrupts and changing the position! Putting a ground on the tool helped a lot, but it's still getting a few, just enough to mess up a long running piece. Next step is put it in a grounded box.

[cswiger]

Ok, putting some series inductance (390uH) and turning on pullups seems to have helped the spurious interrupt issue - testing now.
I'm going to clean up the sketch, use a stock motor driver library instead of my custom hacked one and the DIY servo driver will be ready.

Might make a version to work with the $13 Rat Shack controller for local-sourcing parts

[Al_The_Man]

If you are running the electronics out in the open like that next to a Dremel, I am not really surprised you are getting spurious issues!?
Also a R/C snubber across the motor may help also the Dremels have Universal motors which are notoriously noisy.
Al.

[cswiger]

Thanks! I'll look into the spark suppressor snubber thing, every bit helps and just a few steps on that z-axis makes a noticeable depth move.

Just popped into the local Radio Shack and picked up their $15 arduino motor controller shield and will target the published sketch to that. It has a pretty beefy heatsink:



I think it's good for 15v / 2A - maybe higher voltage if the motor supply is separated from the arduino supply.

[Paul Strotten]

Hi Thanks for making such project on GIThub

Have spent many 100 hrs working with ATMET 328p IC. Then found your work.
Looks very promising, but cannot get it to build, all OK until I include the plusAFMotor in libraries

C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p: In member function 'void AFMotorController::enable()':
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:49: error: 'DIRA' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:50: error: 'DIRB' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:51: error: 'DIRA2' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:52: error: 'DIRB2' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p: In member function 'void AFMotorController::latch_tx()':
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:63: error: 'DIRB' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:65: error: 'DIRB' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:69: error: 'DIRB2' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:71: error: 'DIRB2' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:76: error: 'DIRA' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:78: error: 'DIRA' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:82: error: 'DIRA2' was not declared in this scope
C:\Program Files\Arduino\libraries\AFMotorPLUS\AFMotorPLUS.cp p:84: error: 'DIRA2' was not declared in this scope

Any help very much appreciated
paul(at)strotten(dot)co(dot)uk
Many thanks Paul