4 Wire stepper motor

Hi everyone, I’m new to the message board, and relatively new to Arduino. I am working on a project which I took a bi polar stepper motor out of a scanner. Its really tiny and would serve my purpose perfectly, but it is 4 wires and I have no idea how to control it. I don’t have any motor drivers, but if I need one I could go purchase one. Please help me figure out how to work this little beauty

Welcome.

Here is a good place to start, and you might also find this useful.

Hungryman00: Please help me figure out how to work this little beauty

I would start by measuring the coil resistance as that will give you some idea of the max current that would flow for a given voltage. But it won't tell you the maximum safe current so the smoke doesn't escape.

I don't know if it is so small that it could be driven direct from the Arduino I/O pins (about 20mA of current) - there was another Thread here a few months ago about a tiny stepper that could do that.

...R

Typically these small steppers need 50mA to 100mA or so, beyond the power of a single Arduino pin (you could perhaps common up pairs of pins and use direct port manipulation, but you still need 8 schottky diodes for free-wheeling, which is cumbersome unless you can use these surface mount bus-protectors: QSBT40 http://www.diodes.com/datasheets/ds30195.pdf

There are little motor controller chips that directly drive these motors, again surface mount...

Hey guys thanks for the help so far, I think I probably need a motor controller, even though i have the diodes, it looks confusing.

I have it hooked up to a small power supply right now with Arduino controlling two transistors that alternate each coil. The motor is responding but I cannot get it to make a full revolution. I read the link from the first response and it said something like you have to power up 2 coils at once(?), but it looked like it was referencing a unipolar motor.

The resistance between coils appears to be about 37 Ohms - I don't know if that matters. Maybe I need a better understanding of how the bipolar steppers actually work? But mostly I need to know what kind of IC/ Program I need to get this baby turning

Thanks

You need 2 H-bridges for a bipolar motor, that's 8 transistors.... And 8 freewheel diodes...

Ok so I went out and bought an Arduino motor shield... putting it together now, let me know if you have any tips for hooking this motor up to the shield... I'm still in need of some programming knowledge too :(