[Al Skierkiewicz]

Originally Posted by jgannon

My low-cost solution is to use a Spike, and turn it on and off quickly to vary the speed.
Has anyone done anything like this? Is there any reason why I wouldn't be able to do this? I see that the switching time for the Spike is 5ms, which is far less than the 26.4ms program loop, so that shouldn't be a problem. Any advice would be appreciated.

Don't use the Spikes in this application. They are just little mechanical relays and a rapid switch with an inductive load will kill them very quickly. The disconnect currents will eat the relay contacts due to arcing and the poor little relays will over heat from friction and constant switching. They are only designed to handle motors with a small current demand and that is why they are fused at 20 amps.