3 way (SPDT) Switch to alternate light sources?

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Old 02-26-19, 01:12 PM
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3 way (SPDT) Switch to alternate light sources?

Hey guys, quick question...

Instead of using multiple 3-way switches for one run of lights, can you use one 3-way switch to alternate between 2 light sources?

I assumed so but I figured I'd double check...

I want to wire a switch in the garage so it turns a ceiling light on/off, but when it's "OFF" I want power to go to a small motion detector light. I could just run the ceiling light from one "traveler" lug and the motion light from the other "traveler" lug, correct? As long as the neutrals are all connected in the switch box?

Thanks
Brian
 
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Old 02-26-19, 01:27 PM
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It will work as you have described it.
 
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Old 02-26-19, 04:12 PM
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Yes that will work. It is called common instead of traveler.
 
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Old 02-27-19, 11:15 AM
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Is there any way to do this involving 2 switches? As in, two switches to control one light, but when that light is off, another would be powered? Getting complicated here... lol

Thanks
Brian
 
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Old 02-27-19, 12:40 PM
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Is there any way to do this involving 2 switches? As in, two switches to control one light, but when that light is off, another would be powered? Getting complicated here.
Actually this one is not too difficult. Use a pair of double pole double throw switches, which are each like two 3 way switches in one device with a shared toggle.

You will need extra large boxes, namely 28 cubic inches for 14 gauge wiring with power coming into one box and the light wiring going out of the other box.

Note: In a typical 3 way switch the dark terminal is the common terminal and the lighter colored terminals are for the travelers. For each of the two DPDT switches you need to first identify the two sides each with one dark terminal and two lighter terminals..
 

Last edited by AllanJ; 02-27-19 at 12:58 PM.
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Old 02-27-19, 02:25 PM
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Are DPDT switches the same as a standard 4-way from the box store?

I've worked with DPDT switches in guitars but never in a wall switch. Not sure what to look for.

Thanks!
Brian
 
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Old 02-27-19, 03:30 PM
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Are DPDT switches the same as a standard 4-way from the box store?
No. The switches contain internal jumpers and there is no off position.

Not sure what to look for.
You need DPDT center off. Look for a rating of at least 15a at 200v.
 

Last edited by ray2047; 02-27-19 at 05:26 PM.
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Old 02-27-19, 04:48 PM
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Not just DPDT. That won't work. You need DPDT center off.
I don't think center off is necessary, although that might be easier to find.

You can achieve what the op wants by using one side of DPDT switches for ceiling fan light and the other side for motion sensor light. Treating each as 3 way switch.
Center off is necessary only if both ceiling fan and motion sensor light needs to be off.
 
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Old 02-27-19, 05:27 PM
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I have edited my post to eliminate "center off".
 
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Old 02-27-19, 06:57 PM
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If no "off" position is needed why wouldn't a 3-way connected to a 4-way work? Power to the common of the 3-way. Two travelers from there to feed the 4-way. Then then other two terminals of the 4-way could go to the light and motion detector light.
 
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Old 02-28-19, 02:49 AM
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Power to the common of the 3-way. Two travelers from there to feed the 4-way. Then then other two terminals of the 4-way could go to the light and motion detector light.
That would actually work.
 
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Old 02-28-19, 09:07 AM
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Old 02-28-19, 09:21 AM
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You could also use a photocell to control power to the motion detector light. Then you'd just need a single pole to control the garage light.
 
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Old 02-28-19, 09:59 AM
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Be aware that many motion detectors go into different test modes when being turned off then back on again in under a minute. The ones I've seen will either switch to always on, or a test mode where the motion sensor is on regardless of time of day and turns on the light for only 5 sec at a time.
To reset it back to its normal motion detection, you need to turn it off for over 1 minute, then back on.

I can see that potentially being an issue if you turn on the light to get something, then turn it off. You may be able to get around this by switching the light after the motion detector. Or possibly find a motion detector that doesn't do this.
 
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Old 02-28-19, 01:32 PM
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You could also use a photocell to control power to the motion detector light.
I thought about that as well, but if a lamp bright enough to light up the room is installed on the motion sensor light, photocell will detect that and turn itself off.
 
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