I have 5 volt stepping motor 28byj-48. Can we use power supply from old computer? I think they at AT or ATX.. I just need 5 volt but not sure how many amps do I need for two stepping motors. I looked at the label on power supply and it has 22 amps on 5 volts. Will that work with stepping motors?
Reid
microguy:
I have 5 volt stepping motor 28byj-48. Can we use power supply from old computer? I think they at AT or ATX.. I just need 5 volt but not sure how many amps do I need for two stepping motors. I looked at the label on power supply and it has 22 amps on 5 volts. Will that work with stepping motors?Reid
Since that motor needs 0.1A per winding, a 22A supply is more than sufficient!
However some computer power supplies require a minimum load to operate properly
(they assume at least a motherboard is connected), which may mean an extra
resistor as ballast load is needed.
A USB power supply / phone-charger would be adequate for this particular motor due to its low
current draw, note.
There is some info on that motor and driver board on the ArduinoInfo.Info WIKI HERE:
A good load to put on the 5V output of an AT/ATX power supply is a 12V or 6 V automotive bulb like those used in tail lights. You also know when the supply is ON 
I actually built a benchtop power supply out of an old computer PSU...lots of good resources around on how to do this but this is the one I followed: http://jumperone.com/2011/06/atx-power-supply-tutorial/
One of the reasons I wanted a 5V supply with some oomph was that I am working on a stepper-based project with 3 motors that draw 1A each. After hooking up a L298-based driver and only getting a bit of a hum from the motor in any wiring configuration I tried, I discovered that the L298 has a MASSIVE voltage drop (when compared to 5V) of around 2V.
All this to say that you might need more than 5V to drive your 5V stepper depending on how you are driving it.