I'm about to order some stepper motors, uni- or bipolar (can be operated both ways) with 2 phases. Now I'm thinking about drivers and power supply. I think I'm making my own drivers (with simple ULN2003 bridges), or I'll find something else, that's not the problem at the moment. What I'm not sure about is how to choose the power supply. Three motors will be on at the same time (maximum, most of the time only 2) and the datasheet sais 2.0A/phase. Does this mean I have to supply 4A per motor? In which section do I look for such (low voltage, high current) power supplies? All my other projects are powered with abused pc power supplies, but there are 12A devices hard to find.
I just read that you should choose the voltage 10 to 20 times the voltage rating of the motor. So 30-60V, do you agree? Will the specifications change if I dont operate it at the voltage specified in the sheet?
GoingForGold:
I just read that you should choose the voltage 10 to 20 times the voltage rating of the motor. So 30-60V, do you agree? Will the specifications change if I dont operate it at the voltage specified in the sheet?
Only if using a high performance bipolar motor for extreme speed (a CNC rig for instance). You'll then need the suitable constant-current buck-converting drivers. The high supply voltage enables the driver chip to overcome large back EMFs when the motor moves fast.
If you aren't looking for much speed its much simpler (cheaper) to use unipolar motors driven by ULN2803 or similar - then the PSU voltage should be a volt or two more than the winding's rating (6V supply for 5V windings for instance - for 12V the difference doesn't matter).
The datasheet shows the "Ohm law" relation - ie what voltage will reach maximum current. What one would like to know is the voltage the insulation of the windings can tolerate. A "modern" stepper driver chip does PWM to keep the current at the desired maximum level but pulses it with the supplied voltage which is several times higher. In theory the higher voltage will allow you to go for (slightly) higher max step speed and give a little more torque.
I suppose you can just turn the voltage up until it starts smoking, then use less than that on your next motor
Alternativly use a conservative voltage (say 9V in your case) and if that is enough speed/torque for what you final machine is to do, fine. Otherwise beef it up until the motor or your courage gives up. You driver chip will propably limit you to 30V.
Thank you. This would give me the opportunity to use a PC power supply. They have 12V outputs at very high ratings. They are also cheap and probably I have one here I could use.
