Dusk-to-Dawn Photocell Switch for Outdoor Signs, 120-277V

A photocell is a small light sensor that switches power on when it gets dark and off when it gets light. Wired to a sign, it turns the sign on at dusk and off at dawn, every day of the year, with no clock to reset when the seasons change. You may also see it sold as a photo eye, a photo control or a dusk-to-dawn sensor.

This photocell is outdoor rated and works on 120 to 277 V AC. It goes on the line-voltage side of the sign, before the sign's power supply, so it switches the power that feeds the supply. It does not go on the 12 V side between the power supply and the letters.

A licensed electrician installs it. Most photocells of this kind have three leads: line in, load out to the sign, and neutral. Commonly the colors are black for line, red for load and white for neutral, but follow the wiring diagram for the unit in hand.

Where you aim the sensor matters. It needs to see the evening sky, not the sign. If light from the sign or a street light reaches the sensor, the photocell can think it is daytime and switch the sign off again, so the sign blinks on and off at dusk. Face the sensor away from the sign and from street lights; many photocell makers recommend facing it north so the sun does not shine straight into it.

A photocell alone keeps the sign lit all night. If you want it off at closing time, pair it with our sign timer: the photocell turns the sign on at dusk and the timer turns it off at the hour you choose.

Expect some natural variation. On a dark, stormy afternoon the photocell may switch the sign on early, and it follows the seasons on its own. Keep the sensor window clean and clear of snow, dust and webs; a covered sensor reads darkness and keeps the sign on in daylight.

One photocell can switch more than one sign power supply, as long as their total load stays within the rating printed on the photocell. When you order new letters, you can also have us wire a photocell into the sign; it is an option in the price estimator.

A photocell is the right control when you want the sign lit every night from dusk on. If you want it off at a set hour, add the timer; if you want to switch it from a phone, look at the Wi-Fi switch for indoor 12 V signs.

Before the electrician comes, pick the spot for the sensor: somewhere it sees open sky, out of the sign's own glow and away from street lights and porch lights, ideally facing north. Tell the electrician the circuit voltage the sign will use; this photocell handles 120 to 277 V, but the sign's power supply must match that voltage too.

If the sign has several power supplies, add up their input load and compare it with the rating on the photocell.