I'm looking at the Arduino PCB Kit [store.rrrf.org] and find the PWM Driver Board listed in its contents.

I may have missed something but I'm not finding the intended usage for the PWM Driver. If the DC Motor Driver Board and the three Stepper Motor Driver Boards are used it seems the only thing left to control is the nichrome wire heating element. Is the purpose of the PWM Driver Board to control the heater? Why are there three PWM outputs?

Vince

yes, the purpose is to control the heater. you could also control a fan, a solenoid, etc.

there are 3 because its a nice number and the components are cheap.