pacdrive + stepper motor

[wombleboy]

Hi all,

I'm trying to use a pacdrive to control a stepper motor (a cheap stepper + controller board from ebay). The driver board has four inputs (plus Vcc and ground, obviously) which need to pulse high. But the output from the pacdriver uses common anode, which I think it the cause of my problems ...

With the pacdrive output off on a particular output pin, the PD between the pin and ground is around 0.1 volts; PD between the pin and annode is zero. When I tell pacdrive to turn the pin 'on', the PD between the pin and ground moves to around 0.01v, while between the output and anode it rises to 5v.

That'd be fine for an LED, and I could wire them up with a common anode, as the ultimarc website suggests; but how do I make this work with the stepper please?

[CraftyMech]

Steppers come in all sorts of flavors, and have a wide range of drive requirements. A couple questions which will make it easier to get the help you need:

Is your stepper motor unipolar or bipolar, and what is the voltage/current rating?

Do you have any additional info on the stepper motor controller?

[wombleboy]

Thanks, this is it: http://www.ebay.co.uk/itm/321171450549

I'm happy with the concept of pulsing each of the four inputs high, one by one, to achieve a single step in rotation. Just can't get my head round the issue of the pacdrive sending a pulse high relative to Vcc, rather than ground

[CraftyMech]

With the common anode setup you mentioned, the Pacdrive doesn't set the output pin high to turn on an LED, it actually pulls the output pin low (ground). That is why you found +5v between the output pin and the anode when the output pin was "on".

That would be a problem naturally for interfacing with the stepper controller board, where you want to put +5v on the 4 input pins in a particular sequence.

So unless there is a way to configure the Pacdrive to set the outputs to +5v when "on", you may be out of luck and will need to use another solution. Unfortunately, the board that came with your stepper motor is just a driver board (using a ULN2003 Darlington array) and doesn't provide the sequence logic for powering the motor windings.

So an alternative to the Pacdrive then would be to use a microcontroller to interface with the stepper board. This article was actually written for the exact motor/board combo you have: http://www.4tronix.co.uk/arduino/Stepper-Motors.php