Basic Stepper Questions

Hi All,

I've just bought an arduino board, and would like to try getting a stepper moving. I have a stepper from a printer. Its by FDK, now minebea, so its difficult finding the exact data sheet, but I think I've figured its unipolar from whats available. However, I have a few questions which hopefully someone will find quite simple:

1 - The arduino board takes in up to 12V. Can the microcontroller output 12V, or is it limited to 5V?

2 - the motor states it needs 24V, does this mean that I need to output 24V on each pin, or perhaps it needs a couple of pins for power and I can control it with 5V output from arduino board.

3 - There are only four pins. This says to me that there is no separate power, so hints that I do need to put 24V on each pin?

Any ideas?

Thanks

Pete

PS - if anyone wants to recommend a cheap stepper for this, would be appreciated!

Thanks

1) It can only output 5v. 2) Transistors will let you control 24v from a 5v source. 3) Only four pins on what? If there are 4 motors leads, then you have a bipolar stepper motor. They are more difficult to control than unipolar.

There's some good tutorial info about hooking up motors 'n such on this page.

The short answer is that you'll need to add a little external circuitry (probably based on something like the L293 chip) and a separate power supply to run that motor. If you spend a few bucks on a surplus 12V unipolar stepper, the circuitry to run it is a little bit cheaper, and easier to build yourself on a prototyping board. But not hugely so: it's kind of a "Five-and-a-half of one, half-a-dozen of the other" situation.

And Interesting is right: that's almost certainly a bipolar stepper (although I think I did see an oddball 3-phase unipolar once. But they're definitely not common).

Ran

Thanks for the replies.

Yes, I worked out it must be bipolar, which I can appreciate is more difficult to control. I have another with 6 wires (two connected together) which I assume to be unipolar.

I also found some stepper controllers like the L297 which seem to do a lot, but I guess I would need a darlington array to up to 24V most easily. However then I need to get my 12V source up to 24V which would then be another cost, so potentially easier to buy a 12V one!

I've successfully implemented this circuit: http://www.tigoe.net/pcomp/code/category/arduinowiring/51 I am driving a small bipolar stepper and even with this small one the L293 gets hot. For this 24v motor it might be a wise decision that the h-bridge to be used as interface to the arduino, but it should switch on power mosfets that have proper radiators. The mosfets in turn provide the current to the motor coils. While looking at printer boards I've seen circuits that drive a bipolar stepper with a mcu, that switches on in the right sequence darlington arrays that turn on mosfets or power transistors.