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I would like to drive my stepper motor (1.4A rated current, 3.5V, 2,5 Ohm coil resistance). I only own some L293D drivers but I think I will burn it if I just wire the motor to the driver without some sort of current limiting.

Obviously I will loose some torque but that's ok for the moment.

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Or just use a lower voltage ? –  Rocketmagnet Apr 24 '12 at 18:59
    
The Vcc2 pin of L293D is the input for supplying power to motor. Feed it with a 42% (0.6A L293D max rating / 1.4 motor rating) duty cycle 3.5V PWM supply. You can form a simple PWM supply from a large enough transistor controlled by an LM555 in astable mode with frequency set at least twice that of your maximum stepping rate. –  shimofuri Apr 24 '12 at 19:36
    
I'm trying to do this with the components I have. I have an Arduino Mega, a LM317, some small transistors (BC327/BC337, they can handle 800mA). What do you think? –  angaran Apr 25 '12 at 11:45
    
Please see the diagram on the bottom part of page 19 of LM317 datasheet ti.com/general/docs/lit/… on how to create a current limiter. You can chain this current limiter after another LM317 that's used as a voltage regulator (to generate 3.5V). –  shimofuri Apr 28 '12 at 7:47
    
Linear current regulation at the supply is probably a bad idea. The L293D has a minimum motor voltage spec, and a linear (or really any non-pulse) current regulator in the supply will have the effect of reducing the applied supply voltage to limit the current drawn - quite likely below that minimum voltage. More appropriate alternatives would be a chopping drive (which should be driven by current sense, not by fixed duty cycle, as the current through the inductive coil will build during each pulse), or using a power resistor in series with each coil to limit the current at L293D min voltage. –  Chris Stratton Apr 20 '13 at 18:41

1 Answer 1

If thats your only choice of driver. YOu could try to gang the drivers together. but Peak output current,IO(nonrepetitive,t≤100μs): L293D ±1.2A. YOu could use a Current limiting PS and make sure a heatsink is attached.

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I could make one with a LM317? –  angaran Apr 25 '12 at 11:46

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