How to test a relay whether it's working or not?

How to test a relay whether it's working or not ?

 Relay is an electromagnetic device. Basically it has a 5 pins,more pins also available it depends on the type of relay. For industrial purpose,they use 8 pin relays.But all relays working in a same principle. Here we will study about 5 pin relay. This is we used in our projects. The 5 pin relay is shown in fig.

RELAY

Normally, relays are used to turn on the 230v with the help of 5v(different values are available). The testing methods are:

METHOD 1: 

• This is using multimeter. put your multimeter in resistance measurement.
• Make sure your multimeter is working ( By connecting the 2 leads ,it shows zero resistance) 
• The relay shown in fig,we have 3 leads in same line on top of the relay.In that 2 leads on the both sides are coil leads.The center lead also we call as center.

• Measure the resistance of the coil in relay.Normally ,the relay coil resistance is 350ohm + 10% tolerance.  If it shows in between range of that,then your relay is working otherwise it is not.

METHOD 2:

12v relay

• This method is depends on the voltage rating of your relay.
• If you use 5v relay, then take 5v power supply(or choose variable supply to 5v)
• connect the positive and negative leads of power supply to the coil leads. Then the relay changes it n/o ,n/c contacts( You can identify this by hearing "tuk" sound ). 
• If you remove supply,it goes back to the normal state.
• continuously oscillating relays are also not working.

 Identifying N/O and N/C contacts:

• N/O- Normally open.
• N/C-normally close.
• Put your multimeter in continuity,make sure your multimeter is working by connecting the 2 leads of multimeter(it gives beep sound).
• In normal condition,connect positive lead to center of the relay and place the -ve lead in other 2 leads(Any one at a time) in bottom of the relay.
• If beep sound occurs,then it is N/C contact
• Other lead is   N/O contact.
• By connecting supply to the coil,the continuity changes from N/C to N/O contact. 

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