Is anyone here an EE? Help out an ME!!

[78280z]

I am currently an ME student working on a project and I need some EE advice for my electronics.

 

I will be using two motors at 12V that draw 20A max and would like for both of them to be bi-directional. I would like to use a programmable (USB interface) motor controller that I have, but it is only rated for 1.2A max current. It's user manual can be found at http://www.pc-control.co.uk/images/Motor-Bee%20Manual.pdf and it's IC's spec sheet at http://www.pc-control.co.uk/images/L293D%20motor%20driver.pdf.

 

I know that I will have to use the motor controller to control a transistor H-bridge circuit that will handle the higher current. The controller I am using outputs a PWM (pulse width modulated) signal and I do not know the frequency of the signal.

 

I am trying to figure out what transistors to use in the H-bridge. Using BJTs would probably be simplest, but I've heard there are advantages to using MOSFETs instead. However, I've also heard that MOSFETs have trouble handling PWM signals at some frequencies (and since I don't know the frequency of the signal from the controller, this may be a bad idea).

 

Can anyone give me some advice about any of this?

 

Thanks in advance for any replies, I really appreciate it.

[mikeatrpi]

I'd use MOSFETs. You lose some efficiency going through BJT's. I would say you're safe assuming the motor controller will put out a FET friendly period. The internet is littered with circuits as this is a common thing for robotics, otherwise you can buy a bridge from someone like "sparkfun.com".

 

Good luck!

[connorzster]

agreed the BJT route is more than inefficient. MOSFETs is the way to go and worth the extra trouble.