Using Relays To Control Lights Furd's Way


Old 03-16-13, 10:04 PM
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Using Relays To Control Lights Furd's Way

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I am interested in the system you built for triggering the lights from both the doors through relays. Can you give a detailed description of how you set it up and which components you used.

Thank you

Last edited by ray2047; 03-16-13 at 11:14 PM.
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Old 03-17-13, 12:05 AM
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I'll give an overview and then you can write back if you are interested in proceeding.

I installed concealed magnetic switches in the door jambs with magnets in the edge of the door. From these magnetic switches I ran low-voltage wiring to a 6x6x4 inch steel box that contained a 12 volt "wallwart" power supply and a timing relay. I used a Potter & Brumfield model CNT relay but there are others that may be a bit less expensive as the P&B is between $70 and $90 last time I checked. This relay has a plug-in base that made the wiring easier.

The power supply secondary wires go to the relay's power input terminals and the wires from the magnetic switches are paralleled and go to the control contacts. The "hot" lead to the light fixture(s) go to the relay's common and normally open contacts while the neutral leads of all the line voltage are connected together.

The relay is set up according to the instructions for a timed power on and then off one-shot cycle for each time the control contacts (the magnetic switches) change state. This means that as long as one of the doors is open the relay will be closed and the light on. After both doors are closed the timing function will start and after the time-out the relay releases, the light(s) go out and the relay resets for the next cycle.
Old 03-17-13, 06:20 AM
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As they say... there are two ways to skin a florescent light... or something like that.

If you're less into building your own solution, you could use something like this
INSTEON Wireless Open/Close Sensor - Smarthome
Old 03-17-13, 06:30 AM
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Old 03-17-13, 07:01 AM
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I like the Insteon stuff. I bought some for some wall sconces I needed to control on a circuit I couldn't easily install a switch on.

I have some other projects in mind to use it for in the future. We always seem to leave the house and forget to turn on the front light for when we come home. I can install one of their switches for the light and have one of their battery operated remote switches in the car. That way when we pull up, I can hit the switch in the car like a garage door opener. I could also install more of the switches and control several lights with the remote switch.
Old 03-19-13, 05:01 PM
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Okay, I lied. The CNT universal timing relay now costs around $180. I had mine in my junk box. Often you can find time delay relays in surplus for less than $20. I did find a solid state module that sells for about $42 but it is limited to 300 seconds delay. A wallwart supply is ten bucks or less surplus and the magnetic switches are about ten bucks or less. You need to be careful to get switches that are open when in the proximity of the magnet and closed when away from the magnet, just the opposite of most alarm system magnetic switches.

The Insteon system looks good if you don't want to do any work beyond peeling double-sided tape, installing a battery and changing the switch but it isn't cheap. I count up $50 for the wall switch, $40 for the "access point" receiver and then $35 for the magnetic door switch for a total of $125 in parts and NO time delay.

I like my system better and no battery to periodically change. Not that it really matters because the original poster seems to have lost interest.
Old 03-20-13, 06:50 AM
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I do like your solution Furd. I've done many a project with magnetic switches. The problem is that ever since I was young, I've wanted a fully automated house. Now I just have to keep telling myself that not every light in the house has to be networked.

Maybe my next house though...

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