Arduino Transistor Relay Circuit

Here is a simple circuit that uses a bipolar junction transistor bjt to drive a small 5 v relay coil.

Arduino transistor relay circuit.

An ac bulb is used for demonstration. The third leg is connected to ground. So whenever i turn the arduino the first relay is on and its on for 3 seconds and after that it goes off and the second relay is on 3 sec similarly for third and fourth and after fourth all will be off for 3 seconds and after that all four legs will be turned on. Arduino board jumper wires breadboard.

Basically when 5v flow through the 1k resistor to the base of transistor a current of about 0005 amps 500 microamps flows and turns on the transistor. First leg of the potentiometer is connected to 5 volts. Schematic view of a potentiometer and transistor connected to an arduino. 1 x sharp pc817 optocoupler.

Circuit diagram and working. Basically when 5v flow through the 1k resistor to the base of transistor a current of about 0005 amps 500 microamps flows and turns on the transistor. The transistor in this example completes the motor s circuit to ground. Most motors require more current and or voltage to operate.

The parts you will need. The picture above shows the circuit you need to build. I just programmed the arduino and attach with my homemade relay circuit board and connect all four appliances with the relay board. The arduino can only provide 40ma at 5v on its digital pins.

Below given is relay driver circuit to build your own relay module. The optocoupler is the most important part it isolates the circuit from the relay using. The base of the transistor is connected to digital pin 9 of the arduino through a 1 kilohm resistor. In this arduino relay control circuit we have used arduino to control the relay via a bc547 transistor.

We have connected transistor base to arduino pin a0 through a 1k resistor. Thats it our circuit is complete now we can upload the code to the arduino to turn on or off the relay. A cheap general purpose transistor such as the bc548 is capable of controlling a small relay with a holding current of less than 300 ma. Thats it our circuit is complete now we can upload the code to the arduino to turn on or off the relay.

2 x 220ω resistors. A transistor can act as a digital switch enabling the arduino to control loads with higher electrical requirements. 1 x 1n4001 diode. Usually an npn transistor in a common emitter configuration used as a switch drives the relay.