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Discussion Starter · #1 ·
Can I rig a relay to turn on power to an amp that does not have a 12v trigger feature? If so, will it need to actually be two relays (as the 12v trigger output is pretty puny)?
 

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Yes, and I did almost the same thing: I used a 12v. reed relay to control a 120v. relay w/10a. contacts, that in turn controls a 4-pole, 25a. contactor that powers two amps, two sub amps, and other switched electronics. In your case, the 10-amp relay should be sufficient to control the amp directly.


The idea is to place the relays in a box that has a power cord and a receptacle, and a 12v. input for the trigger, and the 12v. relay switches the power relay, which switches the receptacle.


R.S. parts: reed relay , 10-amp relay


Let me see if I can make a schematic. "I'll be back."

Don't crush that dwarf, hand me the pliers!
 

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Okay, I'm back. Here's a diagram:
http://fineelectricco.com/Trigger1.jpg

You may notice the contacts in series on the power relay. Believe it or not, this extends the life of the contacts moreso than paralleling them does.


As a project, I envision using a deep 4"sq. plastic electrical box with a 2-gang cover. One opening could be a regular receptacle, and the other gang with a speaker-terminal insert. A standard 3-wire replacement cord can be brought out of the box using a 3/8" cable clamp (fits a 1/2" knockout).


Most important is making sure the 12v. terminals and their wires to the reed relay are well insulated from the 120v. wiring. I used a little circuit board, shown here , to mount and wire the two relays, and then housed the entire board in a plastic pouch with wires coming out one end.


While I was less than precise on the drawing, you should run the white wire from the power cord to the silver terminal on the receptacle (the neutral), and do all of the switching in the black (hot) wire. The green wire should go to the green ground terminal, and if a metal box and cover are used, this will ground them as well.
 

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Geez, leave it to the master electrician to make it all complicated. Larry, you are incredibly smart, but I think there is a simpler solution.


Why not just go to Sears and buy the duplex plug they make for tablesaws? One plug is an always powered plug, and the other is a switched plug. When current is drawn through the always on plug, then it switches on the switched plug and the same for when you turn things off. No need for the 12 volt relay.


The plug is used for a fan on a tablesaw or router table. When the saw or router is switched on, it turns on the fan automatically to suck out dust. Some people here use these plugs to turn on hush box fans.
 

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I happen to have one of those. I found that my pre/pro didn't draw enough current to trip it; it's not very sensitive, since it's designed to sense the current of power tools.


Plus, the request was for a 12v. trigger.
 

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Discussion Starter · #6 ·
Quote:
Originally posted by Larry Fine
Okay, I'm back.
Thanks Larry, it's pretty much as I had envisioned. Do you know if there's a socket for the bigger relay?
 

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Another option (which I used so that a universal remote would work) is a Monster, or the like, power management/conditioner. Use an AC trigger from a switched outlet on the back of the pre-pro to trigger the switched outlets on the Monster unit. Works very nicely with my Harmony remote.

I did not have a 12V trigger on the pre-pro or power amp (Rotel RSP-985/RMB-1095).


Jeff
 

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Quote:
Originally posted by Larry Fine
Plus, the request was for a 12v. trigger.
He had mentioned that the 12v trigger was puny. So I took that to mean that he didn't have to use it.
 

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Discussion Starter · #9 ·
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Originally posted by Toxarch
He had mentioned that the 12v trigger was puny. So I took that to mean that he didn't have to use it.
What I meant was that the current available on the 12v trigger circuit was perhaps not enough to run from my head end to my amps and energize the coil of a relay switching the 120v to my amp. Ergo, the small step up relay actuating the bigger one.


I greatly appreciate the ideas that have been put forth here.
 

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Is this the sears duplex switch you were referring to: Craftsman Auto Switch


Any idea how much current is required for the device to work reliably? I am trying to find a solution to help a friend cool a 36" CRT in a entertainment center. It fills almost the entire space and there is only three 1.5" holes drilled in the back for ventilation. I wanted something that could be used to turn the fans on only when the TV is on, and he isn't using a receiver or anything else that has switched outlets. This would be perfect to switch a 12V wall wart to power a couple of fans.
 

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Discussion Starter · #11 ·
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Originally posted by BigDanB
Is this the sears duplex switch you were referring to: Craftsman Auto Switch


Any idea how much current is required for the device to work reliably? I am trying to find a solution to help a friend cool a 36" CRT in a entertainment center. It fills almost the entire space and there is only three 1.5" holes drilled in the back for ventilation. I wanted something that could be used to turn the fans on only when the TV is on, and he isn't using a receiver or anything else that has switched outlets. This would be perfect to switch a 12V wall wart to power a couple of fans.
Check out some of the 12v computer case fans. Some are very low noise and would be perfect to exhaust aire from around the TV. They do not draw much current either.
 

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Quote:
Originally posted by pepar
Can I rig a relay to turn on power to an amp that does not have a 12v trigger feature? If so, will it need to actually be two relays (as the 12v trigger output is pretty puny)?
Xantech sells the XAC1 outlet, which has a 15A outlet and 12V trigger. $60-$70 from worthdist.com.


Home brew solutions (try a solid state relay) will be much less expensive.
 

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Discussion Starter · #13 ·
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Originally posted by Drew Eckhardt
Xantech sells the XAC1 outlet, which has a 15A outlet and 12V trigger. $60-$70 from worthdist.com.


Home brew solutions (try a solid state relay) will be much less expensive.
WOO HOO! I'll gladly pay more for an off-the-shelf solution! Thank you.
 

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Discussion Starter · #14 ·
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Originally posted by Drew Eckhardt
Xantech sells the XAC1 outlet, which has a 15A outlet and 12V trigger. $60-$70 from worthdist.com.


Home brew solutions (try a solid state relay) will be much less expensive.
I went to Worth Distributor's website but they want a password to view an product specs. I Googled "Xantech XAC1" and got two other sites, but they only seem to have the IR gear. Guess I'll call Worth tomorrow.
 

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Quote:
Originally posted by pepar
I went to Worth Distributor's website but they want a password to view an product specs. I Googled "Xantech XAC1" and got two other sites, but they only seem to have the IR gear. Guess I'll call Worth tomorrow.
What you are not a ----> "dealer"
 

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Discussion Starter · #16 ·
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Originally posted by ScottF200
What you are not a ----> "dealer"
 

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Quote:
Originally posted by BigDanB
Is this the sears duplex switch you were referring to: Craftsman Auto Switch


Any idea how much current is required for the device to work reliably? I am trying to find a solution to help a friend cool a 36" CRT in a entertainment center. It fills almost the entire space and there is only three 1.5" holes drilled in the back for ventilation. I wanted something that could be used to turn the fans on only when the TV is on, and he isn't using a receiver or anything else that has switched outlets. This would be perfect to switch a 12V wall wart to power a couple of fans.
Yes, that's the one, and a large TV should draw enough to trigger it.
 

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Quote:
Originally posted by pepar
Thanks Larry, it's pretty much as I had envisioned. Do you know if there's a socket for the bigger relay?
Yes, see here .
 

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Discussion Starter · #20 ·
Quote:
Originally posted by Larry Fine
Yes, see here .
Thanks. I've decided to throw money at it and go wth a Xantech AC1.
 
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