Well the question is whether do you just want to control ONE pwm circuit or more fun as well?
YOU WANT MORE!!
The arduino gives you the option to do more than a regular control circuit or a PID.
Let's warm-up with the legendary reference:http://home.highertech.net/~cdp/boilnew/boilnew.htm
classic self-built control pwm based....
This is the current follow-up:http://www.homebrewtalk.com/f51/pwm-boil-kettle-control-159193/
or you get this one:http://www.bakatronics.com/shop/item.aspx?itemid=383
dirt cheap for a pwm kit (cheaper then the arduino or clone), add an SSR to it and have fun uhmm brew beer.
Right now I am brewing electric on 2 x 1500W elements on two separate 20A breakers (apartment brewing) with an modified RPC (roomie pulse control
) which switches on/off in a 2sec cycle - the catch RPC gets tired or looses pace due to beer sampling.
I am lurking at an arduino with 3 SSRs (two for the kettle, one for the HLT) , run HLT and one brew element on the same circuit, and let the software swap the power between the elements (hlt/1 brew) on the circuit.
The beauty of this? Change the sketch (program) on the arduino and you switch from brewhouse setup to lagering/fermentation chamber!! just plug the controls into your Son of Fermentation version with a mini-fridge.
Then you can cycle the fridge trough one SSR and still have two left for the fans (if they are not 12V). And your lager beer will still stay cool if you brew for a few hours.