Speed regulator for model trains

Speed controllers for model trains exhibiting a perfect regulation characteristic are few and far between. With most controllers, speed is load-dependent. Attempts at correcting this annoying circumstance often cause loss of pull, which is, of course, undesirable. The circuit described here uses the reverse electromotive force (emf) generated by the locomotive motor as a correction signal for a pulsewidth control system. In practice, this method results in an appreciable compensation of load variations, so that the speed of the locomotive remains reasonably constant.