relay

[jmoreno150 10+ year member]

looking to install 2 amps. can i use the one remote wire to wire all three or would it be better to use a relay?

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[Prowler573 5,000+ posts]

looking to install 2 amps. can i use the one remote wire to wire all three or would it be better to use a relay?

Huh?

All three what? Or was the original 2 a typo?

My general rule of thumb (and this is a personal thing without any real technical specs to support it) is the HU activating two outboard accessories is fine but if you go to three or more then use a relay.

Many people have reported success running 3, 4, 5, or more items straight from the HU's remote accessory activation output but to me a $5 relay is cheap insurance against burning that remote output circuit which I have seen happen firsthand on a friend's setup.

 

[geowick07 10+ year member]

EDIT: sorry prowler, posted at the same time.

Up to and including two amps, daisy-chaining is fine. 3 and up, a relay is recommended.

 

[azbass 5,000+ posts]

use a relay

 

[qtipextra 5,000+ posts]

Don't some relay's coils draw too much current?

 

[Prowler573 5,000+ posts]

Don't some relay's coils draw too much current?

Too much current for what? I'm not getting what you're meaning.

I've been using a very simple 30a SPST relay (Archer-branded, from Radio Shack) for over three years on the same relay now and haven't had any problems.

I've also got a relay controlling my fog lights with no issues.

 

[azbass 5,000+ posts]

Don't some relay's coils draw too much current?

they are switched from low current (ie HU rem) and are able to run a higher current through em.

 

[qtipextra 5,000+ posts]

Too much current for what? I'm not getting what you're meaning.
I've been using a very simple 30a SPST relay (Archer-branded, from Radio Shack) for over three years on the same relay now and haven't had any problems.

I've also got a relay controlling my fog lights with no issues.

Because the only reason you run a relay is not to burn up the remote lead circuit. The reason those burn up is pulling too much current through them. The relay acts as a load on the remote lead wire (depending on coil impedence) and then, when switched on, allows current from your 12v source to flow through the now closed switch. Either way, you still have current draw on your remote lead wire. And some coils have low resistence. Even at 15 ohms, thats 800 milliamps of current. I'm not thinking specifics here, but for the most part, an amplifier remote lead circuit holds a constant current load of a maximum of 40 milliamps IIRC. So at running one relay, it's equivilent to running 20 amplifiers. (That is if my recolection is correct).

 

[qtipextra 5,000+ posts]

After searching a little bit, I find some with as low as 10 ohms, and I find others as high as 500 ohms. It all depends on the relay you get. That's what my first statment in this post was pertaining too.

In this application, a 400-500 ohm would be the best, as current is around 24-30 milliamps on the remote lead wire (pulled by the coil), and allowing however much needed for your amplifier turn on wires (up to 20-40 amps [as in current] depending on your relay)

 

[jmoreno150 10+ year member]

thanks for the replies fellas. its was supposed to be 3 amps. i just purchased my headunit so ill go with the safe way and install a relay. im pretty new to this industry but ive had interest for a while. at the present time im attending mobile tech training to learn all this stuff and take the m.e.c.p. so far its going good i have installed my entire system with no problem. thanks for the help.

 

[phyphoestilic 5,000+ posts]

I'm running 3 remote wires (daisy/split) off the head unit, no problems so far. Been at least 3 months. And I usually run the system for 2-3 hours at a time. Had a 7 hour road trip before too.