Remote Control Circuit Breaker Using a Microcontroller

Sometimes, we need to switch on electrical loads using a computer program. For example, in a power plant, you might want to switch on a circuit breaker remotely. This can be done using a microcontroller. Let’s discuss how to make a Remote Control Circuit Breaker Using a Microcontroller.

For this remote-controlled circuit breaker we will need:

1. Microcontroller (such as an Arduino)
2. Transistor
3. Diode
4. Resistors
5. Relay
6. LED
7. PC (Personal Computer)

Microcontroller

A microcontroller is defined as an IC that understands commands from a PC through communication protocols. It can use protocols like Serial, Ethernet, and CAN (Controller Area Network) to communicate with the PC.

A microcontroller has got many peripherals like GPIO (general purpose Input Output) pins, ADC (Analog to Digital Converter), timer, UART (Universal Asynchronous Receiver Transmitter) and Ethernet and many more peripherals to communicate to the external world.
Digital output from a microcontroller is a low amperage signal.

When you set a microcontroller pin to HIGH, it outputs a voltage of +3.3V or +5V with a current of around 30mA. This is suitable for controlling small loads like an LED.

If we want to control circuit breaker by microcontroller pin then we require a driver that can source the required amount of current to the load to switch on. You need a component in between your microcontroller and the device that would be controlled with small voltage and current. Relays and transistors are most often used for this purpose.

Transistor

Transistor works as a driver in this application which gives the required current to the relay to get it turned on when it is in saturation Mode.

Resistor

Resistors are used to limit the current in LED, transistors.

LED

Light emitting diode is used to indicate whether the circuit breaker is on or off.

Relay

A relay is a switch that is used to control high power electrical load (like Circuit Breaker, Motor, and Solenoid). A normal switch cannot handle a high power load that is why relay is used to control high power electrical load.

Working Principle of Remote Controlling of Circuit Breaker by Microcontroller

When a command is giving to the microcontroller to turn on the load, the microcontroller pin is set to 3.3V (in the above circuit) which turns on the NPN transistor. When the transistor is ON current flows from collector to emitter of the transistor which actuates the relay and relay connects the AC voltage to the circuit breaker which turns on the circuit breaker.

An LED indicates whether the circuit breaker is ON or OFF. When a microcontroller pin is high, the LED is on (Circuit Breaker ON). When the pin is low, the transistor is OFF, no current flows to the relay coil, the circuit breaker is OFF, and the LED is also OFF.

Protection Diode

When the relay is switch off a back e.m.f is generated which can damage the transistor if the magnitude of back e.m.f is more the VCEO voltage of the transistor. To protect the transistor as well as the digital output of microcontroller a diode is used which conducts when the relay is off. This is also known as the freewheeling diode.

Designing

The assumed microcontroller gives 3.3V when the pin is high and 0V when the pin is low. Choose a relay of 12 V and 360-ohm coil resistance then-current taken by the relay to get turn on

This is rated current of the relay.

LED (forward voltage = 1.2 V) takes around 20mA current then resistance R_LED

R_LED value can be chosen to 500 Ω.

R_B can be chosen as 4K to give more base current to transistor GUI (Graphical User Interface):

A GUI can be developed in a high-level language (like C#) that uses the UDP (User Datagram Protocol) to communicate with the microcontroller from a PC. The GUI below controls the digital output of the microcontroller over the UDP protocol.