▷ Reversal of single-phase motor with relays and RF module

In this tutorial, I will show you how to reverse the rotation of a single-phase motor using relays and a radio frequency module to control it wirelessly.

💡 Useful resource: Download the PCB design of the relay board here

Motor origin and necessary modifications

This motor was extracted from a sewing machine. Initially, I tried to reverse the rotation by swapping phase and neutral, but this method did not work. Upon disassembling it, I discovered that it contained an internal capacitor.

To preserve the capacitor, I decided to desolder the connections between the stator coils and the capacitor with carbon brushes, soldering 4 external wires in their place.

The wires were passed through the slots of the motor housing for external connection.

Note: The wires with electrical tape are those coming from the stator coils (Image 1).

Principle of rotation reversal in single-phase motors

To make the motor rotate in one direction, we connect the red wires to red and black to black (Image 4). To reverse the rotation, we simply swap these connections (Image 5).

The power supply (phase and neutral) is connected to the visible white wires at the bottom left of Image 3.

Implementation with relays and RF module

To automate the rotation reversal, we need 2 relays and make the connections shown in the following diagram:

⚠️ Important:

• L and N are connected to the wires with electrical tape (coming from the stator coils)
• The common pins of the relays are connected to the wires in Image 2 (capacitor and brushes)

The motor will remain at rest until one of the relays is activated. When RL1 is activated, the motor will rotate in one direction, and when RL2 is activated, it will rotate in the opposite direction.

💡 Additional resource: Learn how to activate relays with Arduino in this tutorial

⚠️ Important caution:It is essential to wait for the motor to come to a complete stop before reversing its direction. These motors are not designed for direction changes while in motion and could be damaged.

Demonstrative video of operation

💡 Practical applications:This system is ideal for automation projects, sliding doors, electric gates, or any application that requires remote control of single-phase motors.