Relay wiring

[touringcamry]

I am not familiar with relays and just want to make sure I am hooking up this relay correct. I want to use the remote wire from my stereo to run a couple things. I am using this relay so I don't burn out the HU and will draw power directly from the battery.

I drew this diagram from the back of the packaging of the relay.



My understanding is that when the coil is powered, it will throw the switch so I should connect the remote wire to one end of the coil and ground to the other. The remote wire will power the coil and throw the switch.

The com pin should be connected to power and the Normaly open pin should be connected to the positive connection of what I want to turn on when the HU turns on. When the switch is thrown by the coil, this should complete the circuit on the positive end to run the device.

[Anshu]

have you bought your relay yet?
your concepts are correct, but the application is a little differernt
the relay has 4 pins on it which are the contacts, get those hooked up right and dont worry about the coil etc.

[touringcamry]

I have the relay already. It actually has 5 pins, but I won't be using the normally closed pin. I'll put some electrical tape over it.

What do you mean that the application is different?

[Anshu]

ah
i was just saying that in the few times that ive wired one up, if just worried about getting the numbers right,
is the relay numbered?

[touringcamry]

There's no markings on the relay other than on the top where it has some part numbers and voltage markings. This is not one of those relays normally sold as "automotive relay" that is a little black cube and has 4 or 5 1/4" tabs on the bottom.

I just needed to make sure I knew what I was I was doing.

[Anshu]

thats weird, there should be some near the tabs

when i wired my first one up, i got a 9v battery and a test light. Best way to learn IMO

[touringcamry]

I have a 12 power adapter somewhere, I'll mess with that first and my multimeter since I don't have a test light. The coil needs 12 VDC.

Thanks.

[88 LE]

Originally Posted by touringcamry

My understanding is that when the coil is powered, it will throw the switch so I should connect the remote wire to one end of the coil and ground to the other. The remote wire will power the coil and throw the switch.

Correct.

One end of the coil has to be positive (remote turn on lead from hu) and the other has to be negative (ground).

It doesn't matter which side of the coil is positive or negative.

The com pin should be connected to power and the Normaly open pin should be connected to the positive connection of what I want to turn on when the HU turns on.

Yup.

You can connect the com (common) pin or normally open (NO) pin to constant +12V. It doesn't matter which pin is connected to constant +12V, since these 2 pins connect together when the relay is triggered.

Just don't connect both to constant +12V.

Originally Posted by Anshu

the relay has 4 pins on it which are the contacts

That would be a SPST (single pole single throw) relay.

Theres also SPDT (single pole double throw) relays, which have 5 pins.


You can use either one. Just that on the SPDT relay, one of the pins is not used.


http://www.nteinc.com/relay_web/R51.html

[touringcamry]

The relay I have is SPDT. I just won't be using the normally closed pin.

The relay not like those ones that you provided a link to. It is slightly larger than one regular 4x2 Lego block.

[touringcamry]

The relay is going to piggy back off of the constant +12V and remote wires on the amp, read in parallel. The constant +12V has a 80A fuse by the battery and is 4AWG.

Since I'm going to be wiring up this relay with 18 AWG wire is it a good idea to put a fuse on the 18 AWG wire between the amp and the Com pin on the relay. The contact on the relay is rated for 10A @ 24VDC. I will need 4W @ 12V so a 500ma fuse should suffice I think. Is this neccessary or just redundant?

[Anshu]

i would, what are you wiring up
Always better to be safe then sorry