Why do we use transistor in relay?
A transistor in between will allow a 5V signal from the Arduino to switch a 12V signal via the transistor to the relay – thus turning it on. 2) The transistor provides protection. In the event of a back emf voltage spike or some other undesired event only your transistor will be blown, instead of the entire Arduino.
How does an SPDT relay work?
The SPDT Relay(30A) is a high quality Single Pole Double Throw Relay(SPDT). The Relay consists of a coil, 1 common terminal, 1 normally closed terminal, and one normally open terminal. When the coil of the relay is at rest (not energized), the common terminal and the normally closed terminal have continuity.
How do electronic relays work?
Relays control one electrical circuit by opening and closing contacts in another circuit. As relay diagrams show, when a relay contact is normally open (NO), there is an open contact when the relay is not energized. When a relay contact is Normally Closed (NC), there is a closed contact when the relay is not energized.
Can a transistor be used as a relay switch?
Transistor as a Switch for Relay Transistors are capable of driving small relays without any problems. Usually, an NPN transistor in a common emitter configuration used as a switch drives the relay. Here is a simple circuit that uses a bipolar junction transistor (BJT) to drive a small 5 V relay coil.
Where does the current go in a SPDT relay?
In figure 1 no DC voltage is applied to the coil so the terminal T is connected to contact 1 therefore the current can flow through fan 1 and it cannot flow through fan 2.
How does the single pole double throw relay work?
So basically you can see the SPDT relay as a way of switching between 2 circuits: when there is no voltage applied to the coil one circuit “receives” current, the other one doesn’t and when the coil gets energised the opposite is happening. How does the Single Pole Double Throw relay works?
Which is more reliable a relay or a transistor?
A relay may have many contacts, such as double changeover poles to implement complex logic. A disadvantage of a relay is that it is an electromechanical device and therefore less reliable than a transistor. The contacts may burn out, and the mechanical parts such as the armature may fail over time.