wondering about the electrical relay..?

[sonaiko]

i have heard about the electrical relay but never seen or used one.

What i know is, it has to have an input voltage, so it can turn a switch ON or OFF between 2 terminals. is this true?

can i use the input levels as 5v (to make the switch close) and (0v) to make it open? if yes plz tell me what relay model i should get.

thanx.

 

[Pyroandrew]

There are hunderds, if not thousands of different relays. The way they work is as follows;

You pass a current through the coil (the inputs, does not matter which way in most). This causes a magnetic field to develop and this attracts an armature. On the end of the armature are contacts which make up the switch.

Most relay's coils are rated at either 6V or 12V, but 5V is enough to switch a 6V coil and usually enough to switch a 12V one.

This is a very simple 5V relay
**broken link removed**
It is about as cheap as they come and has a clear top so you can see how it works.



There is a bit of lingo that goes with relays.

SPST means single pole single throw. This means that there is a switch that is either on or off. These relays have 4 pins usually, two are inputs (the coil) and the other two are the switch.

The more common SPDT is a single pole double throw, this is where the pole (one of the pins of the switch), is connected to one of two other pins. It is connected to only one at a time, meaning it is exactly like a SPST except when it is off the pole is still connected to one of the throws.

You get C, NC and NO pins. These are the 'Common' or the pole, 'Normally Closed' (contact is made between the Common and this pin when the coil is not on, when it is on this pin is disconnected from the Common), and then 'Normally Open' (when the coil is off there is no contact between this pin and the common, when it is on this pin is connected to the Common).

You get DPDT and MPDT, these are double pole double throw and multi pole double throw, but you can probably work these ones out yourself.

 

[sonaiko]

thanx dude, very much.