Positive Pulse Speed Control for R.C.

change the width of the top logic train from 15% to 20% or 10%. I'm playing with a futuba radio from an old remote control toy car. the speed controller exploded but the receiver still works. i put the receiver on the cro and saw approx 50Hz signal with 3V square wave. so I imagine the control circuit works like this top logic train is the signal from the receiver. bottom logic train is the internal clock which is synced to the receiver but the pulse length is fixed to 15%. when both pulses are equal length, the motor is stationary. when the receiver sends a pulse longer than the internal clock pulse, the top inverter goes high for an instant. This charges the capacitor and creates a sawtooth wave. the top comparator converts this to PWM to drive the motor forward. when the receiver sends a pulse shorter than. the internal clock pulse, the bottom inverter pulses instead. drives the motor backward.

published 10 years ago