Investor · Tewksbury, MA · Member since 2010 · 59 posts · 17 votes
I am wiring some new porch lights on my triple-decker that I would like to come on automatically at dusk. Does anyone know of a standalone or box mounted light sensor? This will control three LED lights wired in series.
Ultimately, this would be weatherproof with conduit connections or be able to be wired into a waterproof box.
Investor · San Jose, CA · Member since 2015 · 76 posts · 64 votes
10y
I've used the Intermatic k4221C 120v stem and swivel dusk to dawn photo sensor. It's inexpensive on Amazon. Around $10-$15. It uses a 1/2 knockout with a rubber gasket, so it's easy to mount to a junction box. Make sure the junction box is weatherproof and use wire rated for a wet location such as THWN. Good luck!
Blue Springs, MO · Member since 2015 · 481 posts · 313 votes
10y
I've used one that was shaped like this before, even though it wasn't that exact model. It worked OK for controlling an incandescent floodlight, and later a compact fluorescent floodlight.
In my application, I could mount it on the same cover as the lamp socket; it was one of those cast aluminum outdoor covers with 3 holes in it. One hole had a plug, one hole had the lamp socket, and one hole had the photocell.
There is another one that's designed to poke through a single hole in the middle of a box cover plate; a plastic nut screws down to hold it in. I've never used one like this, but I've seen them at the store.
Note that all of these need a neutral; they can't be used in a switch loop. In other words, if the power comes to the lamps first, and then to the switch (inside), it's not going to work (unless you wire the switch loop with 3-wire cable, instead of the common 2-wire). If the power comes to the switch (inside) first, you're in better shape.
I did something different on my previous house, where the front door was in a kind of alcove. If I had put a photocell anywhere close to the front door, it would have always "seen" the reflected light from the porch light, and made the light blink on and off. I used an earlier version of a timer like this to replace the wall switch inside the front door. It has a "astronomic" feature, which means you program it with your approximate latitude, and then it "knows" when sunrise and sunset are, and turns the lights off and on appropriately. There's also a manual switch on the front that you can push whenever you want. It won't come on by itself if there is a thunderstorm or some other reason for it to be dark before sunset. This timer does not need a neutral, but it does use a battery; on the one I had 10+ years ago, it took one AAA, which would last about a year.
Investor · San Jose, CA · Member since 2015 · 76 posts · 64 votes
10y
I've seen that kind of switch before. If its going to be in the elements, make sure it is rated for at least damp applications. Weatherproof would be better. Typically we wire lights in parallel so that a malfunction on one light doesn't effect the rest of the lights on the circuit (ie. old Christmas lights that go out when one bulb is unscrewed). Almost all sensor, motion, timer, wireless fan switches, ect will require a neutral for the internal circuit to function. They get around this by using a battery like you mentioned. What exactly are you trying to accomplish?