drive steper motor with bjt or mosfet?

[hamid9543]

hi
for drive stepper motor wich of them is better BJT or POWER MOSFET .and why?

[zuisti]

Hi!
A stepper motor is working ordinarily with a low voltage (5-12, max. 24v) and eats high current.
Hence the mosfet is better for driving: lower RdsOn (small saturation voltage), higher speed..
To my mind ...
Hope this helps!
zuisti

[hamid9543]

hi .help to me very much
should  isolated gate of mosfet(e.x irf540)  from microcontoroler with optocoupler or other device?

[zuisti]

should  isolated gate of mosfet(e.x irf540)  from microcontoroler with optocoupler or other device?

Yes, the power mosfets (eq. IRF540) are usable, with or without an optocoupler...
You can "googling" it (for ex: stepper motor mosfet), there are a lot of usable circuits..
zuisti

[microtest]

you most us a optocoupler if you have a short circuit in the power side you burn you logic and you can drive the gate with 10 V too

[Digix]

optocoupler is waste of work same can be done with one NPN transistor, but easer is to just connect directly to the mosfet gate.
if something will go wrong uC is not so super expensive, if we take in account that chances to damage it are negilible.

if you use bridge mode stepper (not unipilar) then everything becomes little more complicated, since high side mosfets require level shifter.