Wiring a Dusk to Dawn Photocell Sensor





Introduction: Wiring a Dusk to Dawn Photocell Sensor

About: Retired Firefighter 1966 to 1986; Retired Wheat Farmer 1987 to 2003. Drapery Sales 1969 to 1987. 17 year Quintuple Heart Bypass Surgery Survivor; 14 year Melanoma Cancer Survivor. 81 years young.

I bought a photocell sensor on eBay after learning Lowes, Home Depot, and Walmart were either out of stock on them or did not carry them.  No problem, I thought, 3 wires and it should come with instructions.  It arrived, but with no instructions except on the little plastic part (see second photo).  I am NOT an electrician, but usually can handle easy projects.  If it had 2 wires, it should be easy, but with 3......that's a problem.  I went online to instructables, Youtube, and a few other sites.  Although I could not find anything showing what I needed, I did gather enough to attempt it.  Here is my wiring diagram ( third photo) and instructions:


Connect sensor's black wire to black wire coming from house.
Connect red sensor wire to light's black wire .
Connect all 3 white wires (from house, from sensor and from light) together.

Now wasn't that easy. :-)



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42 Discussions

i bought a dusk to dawn flood light a few years ago and out of the box it stayed on all the time so i set it back and used another. today i bought a new sensor for it (hoping that was the problem, but it still stays on all the time, even when shining a bright light dead into the photocell. what do you think the problem is, could the factory have wired it wrong inside the housing. and if so does anyone have a diagram of one. This light is a Uni tech with a vapor bulb and a plug in sensor, and inside looks like a large capacitor is attached.

Thanks! Wife as and I selling rental and had problem with the post lamp. Removed a while back but didn't remember how it was wired when I went to re-install it. You made it easy to do. Thanks!!

The photo above is exactly what I'm installing today. What size drill bit would I need for the light pole?

Their are three wires to and from sensor red black and white I wired each to its color but light still does not work new bulb as well

3 replies

The red wire should be directly wired to the HOT circuit supply wire the black wire should be connected to the black wire on the lamp you are trying to illuminate and the white to neutral.

Either the light is no good or you miss wired the P/C.

The light switch should always remain in the on position for the photocell to operate automatically. Turn the light switch off first to make sure the lights do in fact turn off to isolate the problem to the wiring at the photocell or the photocell itself. If the lights remain on with the switch off (Highly doubtful) you have something messed up.

I will assume the lights do go out when the switch is off.

With the light switch on you need to test the photo-eyes circuit. This type of photo-eye has electronics in it that increase the resistance and stop the flow of electricity when light hits the sensor. Take a bright flashlight, laser etc and shine it directly on the face of the photo-eye for a short time and the lights should go out. If they don't go out you have a defective photoeye. If they do go out then the photo-eye is in a position where it isn't receiving enough daylight to increase the internal resistance to shut off the current flow thru the photo-eye thus turning off the lights. WIth the photo-eye removed from the circuit, and if you have a ohm meter, you can test the ohms thru the black and red wire coming out of the photoeye. When you shine light in the face of the photo-eye you should see a increase in resistance and when you cover up the photo-eye the resistance should drop to close to zero allowing current to pass.

Photo-eyes are pretty reliable and durable, still most likely cause is that its defective.

Hope this helps.

4 replies

That is always a real possibility and most likely the problem. I went on the assumption it was wired correctly because it is pretty straight forward, but then again you never know for sure...

If it's staying on all the time then something's done up wrong. It could just be some sensors turn on for a few mins when initially powered up before turning off and waiting for the light level to drop enough to turn on

Always possible that its too shaded where its at tricking the sensor into turning on.

I had a photocell on my exterior Christmas lights and if the cell was facing into the ground It would turn on much sooner then when I turned it to face away from the ground or wall. So many variables that he really needs to eliminate each problem and making sure its wired properly would be my first step and then covering the sensor with tape or shinning a light into it to determine if the sensor is actually working. I have one on the side of my house for some exterior lights and sure enough the first one I got from the home center was in fact faulty. Noting worse then chasing a problem when the problem is a bad from stock part that one assumes is or should be ok.

How do I wire to one side of a duplex receptacle so that the other side remains hot.

1 reply

Can I use this to wire it in at the beginning of a string of outside lights. I have been looking at a set of 10 outside security lights at a great price but they don't have a photo cell eye to work from dusk to dawn, And if so how would I go about wiring and mounting it to a metal R panel building? Thanks


1 year ago

Will this work when using a 12v battery, solar panel, 12v light, and light sensor to light a flag?

1 reply

Only if the P/C is rated at 12volts DC.


1 year ago

Reading these comments I have but one thing to suggest, open your
wallets and get a skilled tradesman to properly install your P/C's. It
will save your homes and lives.


1 year ago

Thanks—this was quite helpful!

Worked perfectly on my garage lanterns! Thanks for the post!