Thats it our circuit is complete now we can upload the code to the arduino to turn on or off the relay.
Arduino transistor relay circuit.
2 x 220ω resistors.
The transistor in this example completes the motor s circuit to ground.
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.
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.
Below given is relay driver circuit to build your own relay module.
In this arduino relay control circuit we have used arduino to control the relay via a bc547 transistor.
An ac bulb is used for demonstration.
1 x 1n4001 diode.
A transistor can act as a digital switch enabling the arduino to control loads with higher electrical requirements.
I just programmed the arduino and attach with my homemade relay circuit board and connect all four appliances with the relay board.
Schematic view of a potentiometer and transistor connected to an arduino.
Circuit diagram and working.
The optocoupler is the most important part it isolates the circuit from the relay using.
The arduino can only provide 40ma at 5v on its digital pins.
The picture above shows the circuit you need to build.
This video npn transistor based 12v dc relay control drive simple make it this type transistor is a semiconductor device used to switch electronic signals a.
The second leg connected to analog in 0 of the arduino.
Here is a simple circuit that uses a bipolar junction transistor bjt to drive a small 5 v relay coil.
Arduino board jumper wires breadboard.
1 x tip120 darlington transistor is recommended but any one that will handle your relay will work.
Most motors require more current and or voltage to operate.
The base of the transistor is connected to digital pin 9 of the arduino through a 1 kilohm resistor.
The third leg is connected to ground.
First leg of the potentiometer is connected to 5 volts.
The parts you will need.
1 x sharp pc817 optocoupler.
Thats it our circuit is complete now we can upload the code to the arduino to turn on or off the relay.
Usually an npn transistor in a common emitter configuration used as a switch drives the relay.