Help Me Set Up A Relay

**Maheriano** · 09-09-2009, 03:50 PM

So I've got my M2-ATX-HV which doesn't power both of my amplifiers sufficiently. It'll power one but I need both, so someone suggested I hook up a relay to it to get the constant 12 volts required by both amplifiers. I'm braindead when it comes to relays, how do I hook one up?

If I were a guessing man from the research I've done, I buy a 12 volt relay, put the 12 volt power into one side of it, ground the other side, then send the 2 outputs to the amplifiers. Is it that simple?

**Curiosity** · 09-09-2009, 05:41 PM

Almost that simple depending on the relay. An amplifier remote-on uses very little power (with the exception of some like RF punch or really old ones). Do you have both amp remotes connected to the M2-ATX and it won't turn them on, but will turn either one on? The problem is that would be less than what it takes to power a standard automotive relay. Most amps are around 25mA and no greater than 50mA. The bosch type relays use over 120mA so you would want a higher ohm coil at least (and clamping diode so you don't blow the remote-on output).
Something like this: http://www.allelectronics.com/make-a...D-RELAY/1.html
Ground one side of the coil, 12V to the other side, plus one side of the contacts (common) and amps to the normally open contact. Diode connects to the 2 sides of the coil as well like gnd ->|- 12V
Another option which would reqiure much less power would be a 200mA darlington optocoupler and resister. It uses an LED and phototransister instead of coil and contacts. It doesn't handle as much power on the output but should work well.

**Maheriano** · 09-09-2009, 07:19 PM

Wow. I don't know what would be easier, researching how to make a relay work myself or researching what you're talking about!

That's right though, I can power either amplifier fine from the M2-ATX, just not both. It's a common thread topic on this forum, just without any real solution.

**Maheriano** · 09-09-2009, 07:36 PM

I spoke too soon, the second amp won't work no matter what I do. And it is a Rockford Fosgate Punch P325.1. So these require more power?

**treetop777** · 09-09-2009, 08:18 PM

Clarify - are you talking about the "amp turn-on" wire or the "power (+12)" wire can't handle both amps?

A relay should work in both cases, just need to clarify the above and see if i can help.

**Maheriano** · 09-09-2009, 08:22 PM

Originally Posted by treetop777

Clarify - are you talking about the "amp turn-on" wire or the "power (+12)" wire can handle both amps?

I'm talking about the remote (switched) wire not being able to handle both. The power/ground wires are fine, I haven't changed them since I got the new parts. It's just an issue with this power supply that there's not enough power from the J6 connector (amp remote turn on) to keep both (of my) amps constantly on. It'll do the 4 channel speaker (MTX Thunder 4244) amp fine but won't in any way turn on the Rockford. I tried to find the required milliamps for the switched input on the Rockford but it's not listed anywhere. What do I do?

**treetop777** · 09-09-2009, 08:51 PM

This will feed pure +12 to both amp turn-on wires (if they can handle it)

**Maheriano** · 09-09-2009, 09:58 PM

Okay so...
1. How do I find out if they're supposed to be getting 12 volts? Is that pretty common?
2. Which kind of relay do I ask for?

**Bugbyte** · 09-09-2009, 10:26 PM

Originally Posted by Maheriano

I spoke too soon, the second amp won't work no matter what I do. And it is a Rockford Fosgate Punch P325.1. So these require more power?

Just to clarify - have you been able to turn the Rockford Fosgate Punch amp on AT ALL? Ever?

Just want to make sure it works.

If it does, then go with Treetop's suggestion, go down to radio shack and buy a 12 volt relay with at least 2 amp capability. They probably sell automotive relays like this one.

A relay is simply an automatic switch that will close or open a circuit when you put power into it (or take power away from it). A mechanical relay uses an electromagnetic coil to flip the swith on and off. That means you need ground and power to operate the coil and then you want to run you wiring through the switch that it controls. Basically, think of how you wire a simple switch. With a relay you wire it the same way BUT you also have to power the electromagnet to turn the switch on and off.

In treetop's diagram, 86 and 85 power the electromagnet. 87 is simply a continuation of the input from 30. That is, 87 and 30 are where the 'switch' part is. Apply power to 86 and 85 and CLICK! Power flows from 30 through to 87.

As the diagram shows, you attach ground to one side of the coil. You attach accessory line to the other side of the coil. You attach 12v constant in to one leg and run the amp turn ons to the other leg.

**Maheriano** · 09-09-2009, 11:28 PM

Originally Posted by Bugbyte

Just to clarify - have you been able to turn the Rockford Fosgate Punch amp on AT ALL? Ever?

Just want to make sure it works.

Yes, it's been part of my system for 2 years. Unless it died for no reason, it should still be working. And if it did die, it wouldn't turn off the MTX amp when the remote wire is plugged into it.

So I can say with complete confidence that the Rockford amp does work fine. I never moved it from its mount point nor fiddled with the wiring at all in 2 years.

Well, we don't have any Radio Shacks in Canada anymore but I'm going to go look for that relay, thanks for explaining it.

EDIT - I forgot to mention, when I swap the M1-ATX back in to the car, the Rockford amp works fine again. So ya, it works.