We’ve got an outside light in back that’s currently switched by two three-way switches. The circuitry is laid out so the final run of wire to the light is a simple two-wire (with, of course, ground, too) run, from a junction box that’s got the line power for the circuit. LOML has periodically mentioned a desire for a motion detector, but I like being able to turn it on before leaving the house.
Is there any reason that I can’t wire in a motion detector to run in parallel to the switching by the 3-way switches, so that if either the motion detector or the 3-way switches are on, the light is on?
It seems like voltage is voltage, and if both switch and motion detector are on, it’s all fine; and if just one is on, it won’t in some way feed back through the other. But I keep thinking I’m missing something (not uncommon at 61).
Bill Houghton
Replies
The motion detector lights I have allow you to flip the switch on and off twice within 3 seconds which puts the light in dusk to dawn mode until dawn, when it resets to motion detecting... so if you are leaving the house just flip it twice and it will stay on until the next morning.
You can easily do that. Just mount the motion detector on a separate outdoor box. Disconnect the cable from the light and run it to the motion detector box. Then run a two wire cable from the motion detector box back to the light. Hook up the wires as instructed inside the motion detector box.
Use the switching feature as the other poster mentioned to turn the light on permanently if you want.
Make sure you get a sensor with a photo cell feature so it won't go on when it's light out.
Edited 10/10/2009 4:30 pm ET by BoJangles
Thanks. If I understand you, though, you're proposing that I hook the motion detector up in series with the switch, not in parallel. There are times that I want the back light on even if there is no motion about, at least not close enough to the motion detector to set it off.One of the issues here in our not quite rural but definitely not urban town is that we get a lot of night wandering critters - raccoons, possums, the occasional skunk, cats. I need to be able to set the motion detector sensitivity to notice people but not smaller animals, or the light will be on all night.So, if I run, in effect, a wire to the light from the motion detector and a separate wire to the light from the switch loop, both powered by the same circuit, do I run into any problems?
I was assuming that you might want to use the light fixture that you already have instead of buying an (ugly) typical motion sensing combo fixture...and also that you may need to aim the motion sensor in a different direction. My answer covered all bases.
If you just want to replace the existing light with a combo floodlight/motion sensor, you can get that at any store and it will do what you want it to right out of the box.
The motion sensor has selections for different functions. Range, time the light is on, etc. It should also have a photo eye to keep it from coming on in the daytime. If you want the light to turn on and stay on ( like a regular light ) you just flick the light switch off and on in a period of a few seconds and the light will stay on.
If you do want to keep a more decorative light and may want the light to come on when you are approaching from a different direction, I do what I first suggested.
They sell replacement motion sensors for the combo lights. I buy a sensor and mount it on an outside weatherproof box of the same color. I do most of these in new construction where people want a really nice outdoor light and don't want the motion sensor type combo unit visible on or next to it. This way you can locate the sensor anywhere you want as long as it is covering the proper area. The motion sensor has wires labeled so you can easily wire it up in the outdoor box.
You run a two wire cable from the switch to the motion sensor box and a two wire cable from the motion sensor box to the light fixture. Wire it as usual in the light fixture box and wire according to the labels on the motion sensor wires in the sensor box.
You may not be able to do this because you have no access to the wiring in the walls and if that is the case, just buy the right kind of combo unit and it will do what you want.
What drh said will work the easiest.
To maintain the motion dectector function, it becomes a question of training LOML not to turn either of the 3 way switches "off"........suggest switch guards as a reminder.....
Jim
Drawings always help - something I should have done from the beginning.
What I have in mind is laid out in the schematic attached. Will this work?
Bill Houghton
Bill, you are overthinking this thing!! All you have to do is supply a switched hot wire and the neutral wire to the motion detector box. It doesn't matter if it comes from a single switch, a three way switch or any number of switches. The motion detector doesn't know or care where the feed comes from.
It also doesn't matter if the light is on the same box as the motion sensor or if the motion sensor is in a separate box that is wired to the light in another location.
All of the connections are clearly labeled on the motion sensor wires and all you have to do is hook them up as instructed.
The correct sequence is.....switched hot wire with neutral > motion detector > light fixture.
The motion detector must have a neutral feed to operate.
Bo
He wants two groups to have full and independent control of the light:
1) Him
2) Critters
Standard wiring leaves him at mercy of the motion detector programming with regard to all that double-switch-flipping crazyness and the fact that using that function (on most motion detector/light combos I've owned anyway) disables the standard motion detector function until dawn. I guess you could turn out the light and then go outside and shine a flashlight at the photocel to make it think it is dawn to reset it?
Wonder why they build in that dawn-reset part anyhow?
edit: rednek gramer
Edited 10/13/2009 11:27 am ET by Righty_Tighty
If he wants to turn the light on when it is still light outside, he is out of luck. You can't wire it the way he has in his drawing.
The only alternative in a situation like that is to run a 3 wire cable from the switchbox to a double light. One of the feeds would be live and would work with the motion sensor and one light. The other feed would be switched and would work directly with the other light.
You can't wire it the way he has in his drawing
Since all OP wanted was an .OR. I could not figure out why you would say that.
Until I ciphered a bit more. The diagram has a three wire set-up--B1, B2, W. The logic of it was simple, so "looks like' an .OR. (if B1, then llight; if B2, then light)
The problem being that it was also an .AND. (if B1 & B2 ?)
Seems like what would be needed is a relay. B1 to feed relay or B2 to feed relay. If either or both B1 & B2, then R1 = light.
Given the number of people who want this answer, it's a bit surprising that there is not a product for it. I know I get asked about this for porch lights a lot. MD fixture very handy for not atttracting bugs all night; but not very handy if one is waiting on the pizza dude.Occupational hazard of my occupation not being around (sorry Bubba)
Any idea what specifically is wrong with what you describe as the "AND" scenerio? I don't see what you and Bo are gettig at.
I am not sure what you mean by B1,B2 and W. If B1 and B2 are the 2 3-way switches and W is the motion sensor, then this concept will work.What he is missing is a neutral to the motion sensor.However, with that he has no way of turning off the light if the motion sensor trips too easy or burns out in an On state..
William the Geezer, the sequel to Billy the Kid - Shoe
I don't know what he wants for sure, so I'm really just inferring upon him what I wish he'd try so he can tell us how it worked out!
Seriously though, why do you think he shouldn't wire it that way? What would happen? It's just like wiring it through two single pole switches except one is motion activated. If both are open, nothing. If one open & one closed, light comes on. If both the manual switch and the motion activiate switch are closed, he simply has the same current traveling over two wires before arriving at the same destination.
The only thing I can guess might go wrong is the live hot on the load end of the motion sensor may confuse the electronics (way over my head).
What am I missing?
The most glaring error in his wiring diagram is that the motion detector is not connected to the neutral wire. Since the device is actually a powered switch, it must have both lines to function. Beyond that, there is the other problem you pointed out.
The drawing you had the link to is a really good idea. As you said, it wouldn't work for him, but in new construction it would be easy to do.
I have never had anybody ask about turning the light on manually in the daylight so that it is on when they get home. I really can't figure out why anybody would want to do that if the motion sensor light is working, but apparently there are people that want that feature.
Your drawing would certainly solve that problem.
Wish I'd wired mine that way. Other folks here wire other things in parallel (usual discussion is a single remote bath fan serving two bathrooms). But I don't know that the electronics in the motion dector won't be confused by a live hot on the load terminal.
I don't like using the built-in double-switch-flip override function of my motion lights since it overrides the motion-only function until dawn.
Check this out:
http://www.geocities.com/bonezphoto/misc/Switchable-motion-detector-light.gif
This schematic probably isn't applicable in this case as I don't think it could be made to work with 2 three way switches (ideas?).
However, it is a pretty smart looking alternative where only one switch is used and it would avoid my question of the live hot wire on the load terminal of the motion switch confusing the electronics.
(not taking credit for the scheme, I found it here of all places: http://www.homegardenguides.com/garden-forum/home-repairs-forum/190750-wall-mounted-motion-sensor-light-question-idea.html#post962520)
EDIT: How about if the OP uses the above diagram modified by inserting a 4-way (in place of one of his 3-ways) in line between the motion switch and the 3-way? Sweet, eh? Think I'm gonna do this myself now. THANKS BILL! I had quit brainstorming on this until you brought it up.
Edited 10/14/2009 4:22 pm ET by Righty_Tighty
On this topic I have a kind of similar question. I have an exterior light fixture that uses two separate wall switches. With a regular bulb it works fine and you can turn off and on from either switch. I put in a bulb with motion detector built in and the light will not come on at all from either switch. Is it the triggering mechanism used to adjust motion vs just on failing because of the 2 switches? The motion bulb works just fine in other fixtures, just not the one with 2 wall switches. Any advice would be very helpful!