I am interested in using the PWM feature of the Arduino to power a big, old 12V 30 Amp motor. I know I could just use a relay to turn it on/off but I'd like to control the speed of the motor with PWM, has anybody controlled a motor like this with arduino before?
Yes, many people have. If you want direction control you'll want an H Bridge (http://en.wikipedia.org/wiki/H_bridge), however - given you want to draw 30A, an H Bridge IC isn't suitable. Therefore, you'll have to build your own H Bridge out of MOSFETs and their appropriate MOSFET drivers. Look in the first few pages of this forum section, there's been lots of threads recently on FET drivers etc.
Similar questions come up once or twice a week. In the grand scheme of things,
30A is quite a lot of current, and you need a well-designed professional controller.
Pololu has some that can do 25A or so.
You can also find others via google search on "high current h-bridge", but will probably
have to connect to a board separate from an Arduino shield.
I am interested in using the PWM feature of the Arduino to power a big, old 12V 30 Amp motor. I know I could just use a relay to turn it on/off but I'd like to control the speed of the motor with PWM, has anybody controlled a motor like this with arduino before?
Thanks!
Any more details of the motor? Definitely a standard brushed DC motor? 30A normal load? or 30A max?