12V variable speed motor control?

What hardware is required to accomplish controlling a 12V 30A max. draw DC perm. mag. motor? I think the PWM command is appropriate, but not sure how to do using high current. Will high current (automotive type) mechanical relays pulse to vary volts, and is this reliable?

Thanks

HPWM is one method. Using 1 MOSFET(or more in parallel) to drive your load is the way to do it.

Using Bosch relay or else other automotive one will do nothing else than noise and burn in few minutes/hours/seconds.

My 16C711 doesn't have HPWM, so do I use PWM with RC circuit or is an analog output an option?
Can PIC's 10mA output drive the MOSFET directly?
Any MOSFET suggestions in the 15A range?

i would sggest you to change your PIC and use a flash version that have a PWM module in like 16F88, 16F628 and how many other ;) Usually i use PIC16C711 on my pin board.

BUT it's not impossible. Depending of your programming skill you could use internal timer interrupt to produce you PWM. A bit tricky but not impossible. i still prefer the use of internal PWM... make everything soooooooooo simple and keep my few last hairs on my head.

Yes a 25 mA PIC i/o can drive a MOSFET. But for safety sake and for high current driving, i would prefer to use opto-isolator between the PIC and the MOSFET.

some cheap opto-isolator PS-2501-1

some MOSFET that spring to mind now IRFZ44N, IRFZ48R, HUF75339P3.

So to be clear, I cannot simply use PWM command of PIC BASIC PRO with 16C711? (I have 16C711 chips already). What if I use external RC as see in PBP manual? Still no PWM control? My programming skills don't include timer interrupt experience.

I have researched the MOSFET's and have found that FP30N06LE MOSFET N-CH LOG 60V 30A TO-220AB can be directly driven by logic level. I am going to put a simple resistor network to assure MOSFET remains off upon power-up. It also restricts the PIC output to a safe level. Still need an OptoIso?