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Old 01-30-2013, 08:16 PM   #1
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Electrical 120v relay for DC control


I'm a newcomer here, and did a quick search but didn't find my topic so hope I'm not repeating anything here.

I have been searching via Google for an electrical relay that will accomplish the following objective:

I have an intercom/gate controller box mounted on the front wall of my garage which contains LED keypad lights powered by 12v DC. These lights are on all the time as there is no timer or photocell to turn them off in the daytime. No big deal, but I'd like to turn them off to extend the life of the little LEDs (there are 4 of them on 2 circuit boards mounted around the keypad). Coincidentally, I have soffit lights over my garage door that are controlled with a timer switch. I thought if I could find a relay, I could insert it into the power feed to the soffit lights so that when the timer turns them on, the energized relay could close a set of dry contacts that I would wire into the 12v supply lead to the LEDs. So far, I haven't found a simple relay that does this. I planned to mount it in an electrical box installed in the power feed to the soffit lights, and then just run the 12v DC wires from there to the controller box.

I'd appreciate any info on available relays for this type of application. My alternate approach will be to install a separate 12v timer in or near the controller box. The only reason I'd prefer to use the existing timer for the soffit lights is that it can be programmed with GPS coordinates that allow timer to sync with sunrise/sunset etc.

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Old 01-30-2013, 08:55 PM   #2
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Electrical 120v relay for DC control


if the LED's are a part of the circuit board, its not worth the effort. though look up the model of the system and see if there is a way a to program the key pad to turn off unless a button is pushed.

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Old 01-31-2013, 12:56 AM   #3
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Electrical 120v relay for DC control


Quote:
Originally Posted by redman88 View Post
if the LED's are a part of the circuit board, its not worth the effort. though look up the model of the system and see if there is a way a to program the key pad to turn off unless a button is pushed.
Thanks redman. I will check as you say. But the LED's are mounted on dedicated circuit boards placed around the keypad, with 8" 12v and ground wires connecting the 2-board assembly to the DC power strip on the main circuit board at the back of the box. So it would be easy to intercept the 12v wire and route it through a dry-contact relay switch. It is an Aegis 4000 system and I don't remember seeing any info in their literature about being able to program the lights, but will ask the local distributor who sold me the new LED boards. I think there may have been a photocell option, but I'd prefer a timer so they don't stay on all night. There are 4 homes in our development that were built in late 2006, and the Aegis LEDs were dead in all 4 of them. Replacement cost of the light assembly package is about $40, so I'd like to get a longer life from them.
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Old 01-31-2013, 08:52 AM   #4
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Electrical 120v relay for DC control


Grainger would have what you need and if you have a better Radio Shack in the area they would too.
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Old 01-31-2013, 10:21 AM   #5
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Electrical 120v relay for DC control


Search google.com for the words...

contactor 12vdc

The word "relay" is used for those mounted on electronic circuit boards, the word "contactor" is used for relays which can be mounted in an electrical box and used for 120v or higher, and the word "solenoid" is used for automotive relays!

They are all the same except for how they are mounted/connected. They are all "electrically operated switches".
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Old 01-31-2013, 11:32 AM   #6
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Electrical 120v relay for DC control


Quote:
Originally Posted by PoleCat View Post
Grainger would have what you need and if you have a better Radio Shack in the area they would too.
Thanks PoleCat. I had come across Grainger in my recent search, and I think I've found a unit that might work. I just wish they had schematics so I could be more certain which model is right.
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Old 01-31-2013, 11:36 AM   #7
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Electrical 120v relay for DC control


Quote:
Originally Posted by Billy_Bob View Post
Search google.com for the words...

contactor 12vdc

The word "relay" is used for those mounted on electronic circuit boards, the word "contactor" is used for relays which can be mounted in an electrical box and used for 120v or higher, and the word "solenoid" is used for automotive relays!

They are all the same except for how they are mounted/connected. They are all "electrically operated switches".
Thanks Billy_Bob. Your clarification of terms helps. After searching under Contactor 12vdc, I realized that I needed to search under Contactor 120v since the switch will be activated by 120v voltage appearing on the coil, and the switch itself will complete the circuit for my 12v DC wire to the LED strips. I've found some potential candidates, but without wiring schematics I'm still not clear which ones might work. I think I just need a SPST switch for my needs.
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Old 01-31-2013, 11:36 AM   #8
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Electrical 120v relay for DC control


why not just splice in a photo cell that is the correct voltage for the boards, you could get those from Radio shack?
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Old 01-31-2013, 11:44 AM   #9
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Electrical 120v relay for DC control


Quote:
Originally Posted by redman88 View Post
why not just splice in a photo cell that is the correct voltage for the boards, you could get those from Radio shack?
That is one of my options, and I think the unit like the one in the link below (if available for 12v DC) may do what I want. I planned to call them today to see if they have one for 12v DC. My preference is to be able to shut the LEDs off in late evening rather than leaving them on all night until dawn.

http://1000bulbs.com/product/3321/ELEC-K4021C.html
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Old 01-31-2013, 12:06 PM   #10
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Electrical 120v relay for DC control


The relay is easy to find and cheap to buy. Make sure the contact (switch) rating is sufficient as far as DC current.

Your search will be for a 120 volt relay.

This relay pictured below is self contained and requires no base or any other parts to make it work. It can be mounted most anywhere and the connections can be made with wire nuts.

This is only an example of the many differing styles of relays.
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Old 02-01-2013, 06:11 AM   #11
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Electrical 120v relay for DC control


Merged your threads.
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Old 02-01-2013, 08:04 AM   #12
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Electrical 120v relay for DC control


Many of the general use relays have two sets of contacts, NO & NC for normally open and normally closed. You would want to use the NO contacts so no connection is there untill the 120V energizes the coil.
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Old 02-06-2013, 08:17 PM   #13
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Electrical 120v relay for DC control


Update: I finally located the perfect relay. It is model RIBU1C. Costs only $10-14 depending where purchased. Arrived today, did a quick test using an outlet for power and put my meter across dry contacts and it will work perfectly for my application. It only measures about 1" x 2" and can mount directly to a junction box. It can be wired as NO or NC.

Thanks for all the help here guys!
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Old 02-06-2013, 10:03 PM   #14
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Electrical 120v relay for DC control


LEDs have very long life. If in the unlikely event they stop working you can replace them for about $0.03 each. Tear one out of an old electrical discard and they are free.
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Old 02-07-2013, 11:51 AM   #15
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Electrical 120v relay for DC control


I subsequently determined that they may be neon lights, not LED lights. Aegis specs say 15000 hour life. Here is a photo of one of the 2 boards.
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Electrical 120v relay for DC control-padlights.jpg  

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