Microprocessor control of a 12Vdc motor

[ptewright]

Hi,

Can anyone tell me what are possible ways to control a 12Vdc motor from a microprocessor? I have a 12Vdc supply, but the output from the microprocessor is 5Vdc, so what do i need to add to interface between these components?

Thanks

 

[bmcculla]

The best way is to use a NMOS MOSFET as a low side driver and use the PWM output from your processor as an input to the FET gate. Depending on how much current the motor takes this should work. If the motor takes a lot of current or the MOSFET gets hot while in use you can add a MOSFET driver to drive the FET gate with 12V. If you just want on/off control you dont need to wory about the PWM.

Brent

 

[TillEulenspiegel]

Do You need speed and direction control? What's the current draw of the motor?

 

[crust]

Is it is a closed loop (i.e. computed measures and controls speed/direction) or open loop (i.e. computed just controls speed/direction but does no measuring)?

 

[ptewright]

it's a closed loop.
the current drwa is probably around 4 amps.

 

[ptewright]

The best way is to use a NMOS MOSFET as a low side driver and use the PWM output from your processor as an input to the FET gate. Depending on how much current the motor takes this should work. If the motor takes a lot of current or the MOSFET gets hot while in use you can add a MOSFET driver to drive the FET gate with 12V. If you just want on/off control you dont need to wory about the PWM.

Brent

Could you suggest some NMOS MOSFET and MOSFET drivers (ie part #s)that I should get?
Thanks :roll:

 

[bmcculla]

Go to digikey.com and do a search for mosfet. Digikey has a great parametric search. Look for something in a TO-220 package that can carry the current required for your motor. Same idea for the mosfet driver (you might not need a mosfet driver if you arn't putting much current through the mosfet).

Brent

 

[Nigel Goodwin]

Go to digikey.com and do a search for mosfet. Digikey has a great parametric search. Look for something in a TO-220 package that can carry the current required for your motor. Same idea for the mosfet driver (you might not need a mosfet driver if you arn't putting much current through the mosfet).

I would suggest looking for much higher specified FET's, your motor has basically three current requirements (actually a spread across the full range).

1) No load - low current.
2) Normal use - medium current.
3) Stalled - extremely high current.

If you only select your FET's for normal use, if the motor stalls it will probably blow them.