Diode acts as a protection for transistor against back emf induced through relay coil during transit conditions.
Arduino relay transistor diode.
The coil of the relay needs a large current around 150ma to drive the relay which an arduino cannot provide.
In this arduino relay control circuit we have used arduino to control the relay via a bc547 transistor.
Transistor acts as a switch to control the 12v to relay coil.
1 x tip120 darlington transistor is recommended but any one that will handle your relay will work.
Arduino tricks is the online education platform which teaches students every day that too completely free of cost.
The picture above shows the circuit you need to build.
1 x sharp pc817 optocoupler.
The design of the circuit is described here.
Circuit diagram and working.
Connections to the household appliance are not shown.
In this project the npn transistor 2n2222 drives the relay when the npn junction gets saturated.
The parts you will need.
We have connected transistor base to arduino pin a0 through a 1k resistor.
B sc engineer in electrical and electronic engineering.
The optocoupler is the most important part it isolates the circuit from the relay using.
Arduino board jumper wires breadboard.
The project is used to demonstrate the high voltage driving capabilities of a relay using arduino uno.
Therefore we need a device to amplify the current.
Below given is relay driver circuit to build your own relay module.
The base terminal of the 2n2222 transistor is connected to any of the digital i o pin of the arduino through a 1kω current limiting diode in this project base is connected to pin 7 of arduino.
The following picture depicts how to connect the different parts using a solderless breadboard jumper wires a transistor a diode a relay a push button and two 10k resistors.
1 x 1n4001 diode.
In this project the npn transistor 2n2222 drives the relay when the npn junction gets saturated.
The following arduino program completes the post.
2 x 220ω resistors.
An ac bulb is used for demonstration.
Resistor adjusts input current from arduino to the transistor.