DC Motor Soft Starter Using Arduino Uno Board

Motor starter reduces the load, torque and current surge of a motor during startup.

- A. Samiuddhin

On starting, the motor takes more than five times the normal running current. This overheats the motor’s armature winding and creates a sudden voltage dip in the power supply, which can be avoided by using a motor starter.

There are many types of motor starters. Here we describe an electronic DC motor soft-starter using Arduino Uno board. This circuit controls both softstart and soft-stop timings through pulse-width modulation (PWM).

Circuit and working

Circuit diagram of the DC motor soft-starter is shown in Fig. 1. In addition to Arduino Uno board (Board1), it uses PIC817 optocoupler (IC1), p-channel IRF9530 MOSFET (T1), 1N4007 rectifier diode (D1), 12V DC motor (M1) for testing, bi-colour LED (LED1) and a few other components.

Arduino Uno board is an important part of the circuit that generates PWM signals. Pushbuttons (S1 and S2) are used to soft-start and softstop the motor. The bi-colour LED indicates whether the motor is in soft-start or soft-stop mode.