“The project presented here is a low-cost solution to control high power brushed DC motor speed and direction. Traditional DC motor controllers are based on solid-state circuitry known as H-Bridge. Here we have made an H-bridge configuration using high current 2 x relays which can handle high voltage as well as high current. Additional MOSFETs are used to control the speed of motor. These MOSFETs can be removed in case of only direction control required, short the Drain and source pin of MOSFETs. The project requires 3 control input signals, all inputs are optically isolated to prevent noise and high voltage going in to logic circuitry. A large-size heatsink is a must on MOSFET.
The project requires 3 input signals, 2 x TTL 3V to 5V for direction control and one PWM 0 to 100% Duty Cycle for speed control. Operating supply is 12V DC for logic circuit and relay, Motor supply 12V to 90V DC, Load up to 20A.”