Relay Application Ques?

Hey guys,

I was researching this board for help with this topic, but it just let me to some other questions.  First let me explain what I am trying to accomplish. I am trying to connect the remote turn on wire from behind my my headunit in my honda to 2 amps and 2 cooling fans.  Here are the questions i have: first, is it really crucial for me to use a relay for this application (can I just splice my remote wire to each accessory or component)?; second, in the diagram that was used, it said that pin 87 was to be connected to a 12v source fused- with the radio there are 2 12 volt sources- the continuous from the battery and the one when the ignition is turned on - not sure which to use; last, i wanted to know what relay to use.  In the relay section it said that I can use an SPDT relay, but I was wondering if I can use an SPST or automotive relay that is 30amps as well.  Thanks for the help.  Sorry if this sounds complicated.

Here is a link to the relay that I am thinking of using from radioshack:

http://www.radioshack.com/product.asp?catalog%5Fname=CTLG&category%5Fname=CTLG%5F010%5F008%5F007%5F000&product%5fid=275%2D226

Sagar

Hi Sagar, you want to use a relay whether it's an SPDT or an SPST (doesn't matter for this application) and you can use either of the two 12V+ wires behind your head unit (preferable the constant 12V+ lead) to connect to terminal 87 of the relay for the accessories you intend to turn on, just be sure to fuse it.

the12volt

Thanks for the reply.  Is it ok to use an automotive relay?  And can I use the relay in the above link from radio shack (that is the only store around me that I know that has them)?  Thanks once again.

Sagar

Oh yeah, i also didnt understand the type of fuse to use?  30amp or 40amp?  Im running 2 fans @ 5amps each and 2 amps (a 1200w that draws 114amps and a 200w that draws 30amps).  Thanks

Sagar

The amplifiers should be fused at the battery and the turn-on lead of each will draw minimal current (less than 200mA) . Since you intend to power the fans off of this relay and you'll likely have the fans near the amplifiers, you can locate the relay near them as well and connect terminal 87 of the relay to your power distribution block with a 10 amp fuse instead of connecting to a 12V+ source behind your head unit. If you were only connecting to the turn-on leads of amplifiers, processors, etc, then I'd say it would be okay to use a source behind your head unit as I described in my previous post. 

the12volt

ok,

lemme go over this to make sure i have the right idea.  My distribution block converts a 2gauge to 2 4 gauge outputs.  So I can connect one of these outputs to the 87 pin on the relay fused with 10amps. Then i run pin 30 to the amplifiers and fans? or just the fans? and if this is the case, then how do i power my 2nd amp considering that my 2nd output from the dist block is now used for the relay?  Sorry for the confusion. I also included a small drawing that has my setup, and i think the way that you you are telling me to hook up the relay.  Let me know if im wrong.  Thanks.