4841 Switches and Relay

What is a switch use for
A switch is basically use to make or break a circuit


Switch Electronics abbreviation
SPST = single pole, single throw 

SPDT= single pole,double throw

DPST=double pole,single throw

DPDT=double pole,double throw

Relay
Relay is a switch that operates electrically.

How it works
Picture on the right. The top spring is connected to a leaver that holds it connected to the outer right leg, when voltage is pass through the coil it creates a magnetic field when the correct voltage passes through the coil  (you can buy relay that responds to 6v or 12v) the magnet gets strong enough to attracts the armature and the leaver which connects to the middle leg, depending on how you connect the relay to the circuit this make or breaks the circuit.






http://en.wikipedia.org/wiki/Relay

85  Negative coil 

86  Positive coil

30,87  Terminals Switch normally open (NO)

30, 87A   Terminals Switch normally closed (NC)

85  Negative coil 

86  Positive coil

30,87  Terminals Switch normally open (NO)

Relay with diode

On some relays there is a diode build in to protect circuit components from back EMF (electromotive force)  produced by the relay coil a diode is installed next to the coil.

Car alarm Signal light

Four 4 pin relays switching electric window motor by Roman B

Two 5 pin relays switching electric window