Arduino

Arduino DC Motor Speed & Direction Control using Relays

February 17, 2021 by rasika Joshi

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We outlined how we can control the direction and speed of a 24v high current motor utilizing Arduino and two relays.

Hardware

 1 Arduino UNO 1 5v relay 2 BC547 2 Pushbutton switch 1 IRF540N 1 Single Turn Potentiometer- 10k ohms 1 Resistor 10k ohm 1 CDL4U(E)DD5

Software

 1 Arduino IDE

Summary

We outlined how we can control the direction and speed of a 24v high current motor utilizing Arduino and two relays.

Transistor

Here transistors are utilized to direct current from Vin pin of Arduino to relay which is managed utilized a push-button connected from digital pin to the base terminal of the transistor.

Arduino Purpose

It offers the amount of current required to turn on the relay also the transistor.

MOSFET

It is needed to handle the speed of the motor. The PWM value of voltage determines the speed of the motor.

Current Calculations

The resistance of the relay coil is estimated utilizing relay which turns out to be = 400 ohms

Vin pin of Arduino gives = 12v

So current require to turn on the relay = 12/400 Amps = 30 mA

Working of the bidirectional motor

When no pushbutton is pressed

In this case, no current flows to the base of the transistor, hence the transistor remains off behaves as an open switch.

When one push button is pressed

Some current runs to the base of the transistor via a pressed push button which turns it on. Instantly current simply flows to the relay coil from Vin pin via this transistor which turns this relay (RELAY A) on and the switch of this relay is thrown to NO position. This is the clockwise motion of the motor.

When another push button is pressed

Here other relay turns on. Now current simply flows to the relay coil from Vin pin through the transistor which turns this relay (RELAY B) on and the switch of this relay is driven to NO position. This is the anticlockwise rotation of motor

When both push buttons are pressed

Here current moves to the base of both transistors because of which both transistors turn on (acts like a closed switch). And thus both relay is now in NO position.

Controlling the Speed of DC Motor

MOSFET is switched on and off at high PWM frequency voltage and since the motor is attached in series with the drain of MOSFET, the PWM value of voltage defines the speed of the motor.

Author

rasika Joshi

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