I have two steppers from OKI printer. What current I need to power them ?
500 mA will be sufficient value ?
First :
3.3V number KFL49LLB 741A 5.5 ohm
Second :
5.6V KBL42LLB600R 7.9 ohm
The are four wires (two phase bipolar motors).
I = V / R
- 600mA
- 710mA.
3.3V number KFL49LLB 741A 5.5 ohm
Well, the part number clearly says that's a 741A motor!
JUST KIDDING! 
Indeed AWOL has the right idea: the motor manufacturer is telling you the maximum current the motor will take when a steady DC voltage is applied: 3.3V is the maximum you can apply, so at 5.5 ohms each phase will carry 3.3/5.5=600mA.
Now a stepper motor has 2 phases so if you are trying to find a power supply for this, you will need at least 1.2A, and preferably a bit more for safety (and perhaps also some reserve for powering the Arduino).
Also, you do not HAVE to use this current. You can use less. The manufacturer is telling you the maximum amount before you may damage the motor. The less current you use, the less the motor heats up but the less torque you get.
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The Gadget Shield: accelerometer, RGB LED, IR transmit/receive, speaker, microphone, light sensor, potentiometer, pushbuttons
Ok, thanks guys !
I accdently about this formula
Problem is solved !
I plan to make board with external power(adjustable for both motors) and H-bridge.
Logic is wired thought NPN transistor
( http://www.arduino.cc/en/Reference/StepperBipolarCircuit)