I was reading the DIY for an alarm that was done and noticed they used a relay for the alarm. On the 5701, it doesn't show why one would be needed. Is it only for multiple sirens due to the extra power needed to run the additional siren?

 

Yeah, it's only for multiple sirens. I myself use a relay because I have an interior piezo or two, under-hood DEI 514C in a visible-but-hard-to-reach area, and going to stuff a DEI 514C in the bumper foam. Also if doing the relay thing it's best to have an inline fuse (I used 2 amp, didn't have 1 amp around) going from the relay to the siren (I also did a 15 amp from the power lead to the relay) so that if any siren is cut and grounded out it won't send 40 amps of power to the ground. :-)

 

My question wasn't worded right but at least you figured it out lol. I understand the other relays but why is it needed for the sirens? Is it too much for that much current to split to all three sirens? I'm having the main one under hood and one piezo inside. I figured I could just split the two into the siren + side on the alarm. Correct my thinking if I'm wrong.

 

For a DEI alarm you can use a standard siren and a piezo without any issues. The reason relays are used for multipe sirens is to direct a full amount of current to the sirens without causing the alarm brain to be overworked and to ensure they produce the volume when set off.

 

Ok. That's what I was thinking. So for the 5701, it shouldn't be too much for two sirens correct? Rather do it right the first time.

Thanks again!

 

Just connect the red wires to the brown wire from the brain, ground each siren as you wish, and you should be fine.

 

Correct - I ran a 514C and eBay (but functional) piezo against my Matrix 1 (low end 1-way alarm, $120 at the time) with no issue. One reason I like the relay thing I have set up now is that I'm sure the 2-amp inline fuse will blow now, rather than silencing the interior piezo. With the on-board siren lead I was not sure if it could even do 2 amps of power total.

I do remember that when I was messing around once and put like, 6 mini-piezos together, the brain did not like it. So this should give room for expansion.