Basic Questions about relays

[ibrahim03]

Can anyone please tell me the difference between a 5 pin relay and an 8 pin relay. How do i find out the pinout information of both.
Moreover can I use an ordinary 5V relay to drive a motor in common water pumps?
Also what is the difference between an ordinary relay and a power relay?

 

[v_c]

Can anyone please tell me the difference between a 5 pin relay and an 8 pin relay. How do i find out the pinout information of both.

To figure out the pinout (which will tell you about the difference) you probably need to know the part number of the relay -- can you see any numbers or marks on the relay?

Moreover can I use an ordinary 5V relay to drive a motor in common water pumps?

I think it all depends on how much current you need to carry. Take a look at this


From https://www.acroname.com

The energy the coil takes to close the contacts of a relay is part of the specifications for that relay. This current must be within the range of the logic circuit driving the relay. Many small relays are available that can be driven directly from logic currents of ~20 mA. If the relay being used has a higher current rating than the logic can provide, a transistor can be used to amplify the current from the logic circuit to drive the relay.

One other consideration when using relays is the current spike created by the coil. When a coil of wire has current running through it, a magnetic field is created. This closes the contacts of the relay. When the current is removed from the coil, the magnetic field collapses and this causes current to flow through the wire until the magnetic field is completely collapsed or gone. This can cause a damaging voltage spike back towards the logic circuit. This is called flyback and is avoided in the above circuit with a flyback diode.

Also what is the difference between an ordinary relay and a power relay?

Power rating.

 

[IanP]

It is possible that the 5-pin relay has one set of switch contacts (SPDT) and the 8-pinner has two sets of switch contacts (DPDT) ..
5 --> 2=power 3=change-over contact (see picture below)
8 --> 2=power 3 + 3
but without data sheets one can only speculate ..
See also: "Choosing a relay" in: http://www.kpsec.freeuk.com/components/relay.htm

Regards,
IanP