April 12, 2008
Project: Add photocell (dawn to dusk switch) to existing outdoor fixture.
Time: 30 minutes
Benefits: Eco Friendly, power saver, time saver, esthetically appealing
Cost: $5 – 10 depending on you collection of tools.
Today’s Watthack covers adding a photo cell to a patio light. This light is on our front porch and we typically turn it on when we get home, and turn it off in the morning. That’s just our routine so we don’t forget, but this wastes power as the days get longer. While visiting my big box home center, I picked up a photocell that will mount into the light fixture we have. It’s made as a replacement for Hampton Bay lights with photocells installed, but it’s simple enough to wire into just about any light. And, with a price of 5 – 6 dollars, it’s about half the price of other thread-in photocells.
First let me start off by saying that I’ve tried a few of the screw-in photocells. They are typically more expensive ($10 – $12,) don’t last as long, and generally look like crap when installed in any light with a clear glass globe like ours. Thread in photocells are easy to install, but we get to use power tools with this version; a definite bonus.
The project starts by disconnecting power to the lighting circuit. If it’s a switched circuit, you could just turn off the switch, but if anyone else is home, you are asking for shock treatment. Be safe and take the time to kill power to the whole circuit.
Next, we remove the light fixture by unscrewing the two retaining nuts on either side of the light base. Your fixture will vary, so take your time and locate the hardware you need to remove. Also, if your trusty painter caulked and painted around the light fixture, you may want to locate a utility knife and score the paint between the wall and fixture. This will prevent you from needing to repaint.
Our house was built in 1938, so our wiring is pretty simple. One neutral (white) wire, and one power or hot wire (black.) You may have another wire that is either copper or green which is considered the Ground wire. Disconnect all the wires and pull the fight fixture down. You should have matching colors on your light fixture. If not, take a minute to label each wire so you remember how it goes back together.
Remove any glass that might fall out or get broken while you drill your hole. Also take a look inside your housing and at any bracket that is attached to the electrical box to determine the best location for the photocell on the base of the light. I decided mine would look and perform best if the photocell was at the bottom of the base pointing down. This turned out to be a big mistake. As it would turn out, I didn’t account for the output of the light itself, so the brighter the light got, the more the photocell would try to shut it off. The result was a dimly flickering bulb that was far from useful. To correct this, I will need to move the photocell into an area that is shaded from the light.
I happen to have a drill press in the woodshop, so that’s where I headed to make my hole. However, a handheld drill will work just as well.
Double check you drill bit size – you only get one shot at this, so don’t make your hole too big. After all, the beauty of this photocell project is that it will be hardly noticeable once complete.
You may want to have some blocking to help keep the fixture level while you drill. Start drilling and take your time. The harder you press the hotter the bit gets and you risk denting your fixture. Spray a little WD-40 on the bit or use cutting oil if you have it.
Once your hole is drilled, be careful to not cut yourself on the sharp edge. I used a small file to knock down some of the sharp edges. This step is not necessary since the edge will not be exposed once the photocell is installed – just be careful.
Remove the retaining nut from the photocell and uncoil the wires. This will be a lot easier and safer before the photocell is secured in place. From the inside of the light, slide the threaded shaft of the photocell through the hole you just made and thread the retailing nut back on. If your photocell has adjustments or wiring diagrams on its housing, be sure that this is facing out so they are accessible.
Pay attention to the wiring instructions on the packaging or the body of the photocell. Ours indicated that one of the black wires should be connected to the light, and the other to the black wire coming from the wall. So power would run from the house, into the photocell, then into the light. The photocell acts as a secondary switch that opens and closes depending on the amount of light. One nice feature of the photocell that I purchased is that is actually dims – that is, the more light outside, the lower the light output. Conversely, the darker it is outside, the brighter the light output. Pretty cool!
Connect the black wires based on the directions that came with your photo cell.
Connect the white wires together making sure to tuck them back into the electrical box.
Connect the green/copper wires together making sure to tuck them back into the electrical box.
Replace or tighten any mounting brackets that you removed or loosened to remove the light fixture.
Install retaining nuts that hold the fixture to the electrical box.
Turn your breaker back on and wait for dark. Really, that’s all there is too it. If you are like me and can’t wait, you can block off light to the photocell to see the light turn on.
This was a simple and inexpensive project that anyone with the right tools can do. Not only is it more convenient because we don’t need to remember to turn it on, it save power each day by matching its output with the sun’s. I have a hunch I will be adding a few more of these around the house. If you want to purchase the photocell that I’m
using, the sku is 594-135 and can be located in the lighting section of Home Depot. I hope you found this guide useful and are now contemplating adding photocells of your own.
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