Posted by Circuits Arena on Monday, 17 November 2014
Categories:
CIRCUITS,
RELAY
Relay Driving Circuit is the artlcle explaining Most of the electronic circuits using relay's for the purpose of switch. If the electronic circuits operated by battery source external...
Most of the electronic circuits using relay's for the purpose of switch. If the electronic circuits operated by battery source external load is on the battery source when the relay operates means switch function causes power consumption takes place in this mode. overcome this problem by using relay driver circuit.
Working
Figure shows circuit diagram of the power-saving relay driver where resistor R1 and transistor T1 form a standard relay driver circuit.
- the relay is energised, its pole is pulled
in to make contact with the N/O side, and it holds in that position
with typically 75 per cent of its nominal-rated voltage.
- Power consumed by a relay coil during this
holding time equals V²/R, where R is resistance of the relay coil and V
is the voltage. Here resistors R2 and R3, transistor T2 and capacitor
C1 lower the power consumption after actuation by applying less than the
normal operating power
- When power is applied, capacitor C1
momentarily shorts resistor R2 and allows full voltage across the relay
to pull the pole contact, and then slowly the current through the
capacitor drops.
- Resistor R2 takes care of the current,
ensuring it is just sufficient to hold the relay. The constant current
mechanism formed by transistor T2 and resistors R2 and R3 effectively
drives the relay at very less power.
Components
Diode D1 - IN4001
Transistors T1,T2 - BC547 npn.
Resistors - 1/4 th watt.
R1,R3 - 47k ohm.
R2 - 47 ohm.
capacitor
C1 - 220 micro farad 25v.
Relay - 12v, 400 ohm IC/O Relay
