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Ward indexer - Pololu DRV8825 Stepper Motor Driver

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PekkaNF:
This indexer:
http://www.worldofward.com/rotarycontroller

Bought some years ago and finally got to order keypad and other parts.

Took a little time to fiqure out how to konnect the keypad. Layout was correct, but rows are inverted.

My problem is that the rotary controller seems to be working right and I can measure that all pulses comes out fine from it but the stepper motor does not rotate.

The stepper driver and motor are small, but I want to test the indexer completely, before I comit building the mechanics and rest of the system.

Pololu DRV8825 Stepper Motor Driver Carrier:
https://www.pololu.com/product/2133

This circuit:
https://a.pololu-files.com/picture/0J4232.600.png?f2f6269e0a80c41f0a5147915106aa55

The Ward rotary controller seemst to work fine. PSU for it is 12VDC galvanically separated switched mode powersupply. The linear regulator makes +5VDC. GND is connected to stepper controller GND.

The Pololu stepper controller receives +5V to RESET ja SLEEP pins.
FAULT-signaali is +5V all the time.

Motor current is adjusted to 1A:


PSU to stepper controller is repurposed laptop brick (16VDC/n.7A). Bulk capacitor is 100uF.

I haven't connected or disconnected anytjing with power on.

Nothing heats up, but the stepper bridge is floating, it does not feed the stepper, no matter what I do.

Am I doing something fundamenttaly wrong?

Pekka

John Swift:
this is what I would do for my initial tests

once its working the stepper driver enable can be connected to Steves indexer
and the mode inputs M0 to M2 re wired to set the desired micro step


John

PekkaNF:
Thank you. Enable et.al. have pull-downs, but when I scoped them, I found some HF-componenet.

I ditched ungrounded PSU (12 volt one, that was feeding rotab indexer) and supply both of them from single 16V lap top PSU. That solved the problem.

Stepper is working now and I can shift my interest on mechanics. I need a bigger stepper and some bits to hook stepper on harmonic gear.

Pekka

chipenter:
Insted of a larger motor you could gear down the drive , I have 100 steps per degree with a small motor .

PekkaNF:
That looks pretty nice.

The gear I have is 1:50 harmonic drive. It has a coupling for 8 mm shaft, therefore I'm very much inclined to buy a stepper motor with 8 mm shaft and then stepper motor drive to suit.

I don't have a worm gear, but if I could find a worm wheel that clears 40 mm shaft and fitting screw I would fit that into lathe. I can think many ocasions that lathe chuck index would have been really nice to have.

Pekka

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