Posted by Doug Root on 18th Jul 2020

What Is a Photocell Sensor and Why It Matters

At Atlanta Light Bulbs, unsurprisingly, light bulbs get most of the press. It’s a big part of our business model stressing the importance and significance of the vast lines of light bulbs we sell, from plain old incandescent bulbs to circline fluorescent bulbs, LED lights, HID lamps, UV bulbs, specialty lights and everything else in between.

We also stress to our customers that we are the source - a one-stop-shop, really - for important fixtures, ballasts, drivers, and accessories that make it possible to build lighting solutions into a location so that they work as intended.

All of that is important, including the accessories. Something you will come across in our online store that you might have never seen before is something called a photocell sensor - something that, without a background in electrical engineering, might sound somewhat alien.

They’re actually fairly simple devices, and believe it or not, with a little background information you’ll probably actually be surprised to discover that you already knew what they were, although you may not have known what they were called.

How It Works

In its most basic form, a photocell sensor is a resistor the resistance of which changes in response to its exposure to ambient light. We’ll need to parse this a little bit more for it to make sense.

A resistor is a device that offers resistance; it is built into an electrical circuit in order to regulate the current of electricity through the circuit at a specific point. All materials, at least theoretically, present a degree of electrical resistance.

To keep things simple, we must then offer some explanation of what resistance is, however brief. Electricity is, simply, the flow of electrons along a conductor. Resistance is a quantitative measure of how much a material ‘pushes back’ against a flow of electrons, measured in ohms, which are equal to the voltage divided by the current of a circuit. The higher the resistance is, the harder it is for electrons to flow in that direction against resistance or against a resistor.

Back to photocell sensors - they are resistors that offer varying resistance in accordance with the light that shines on them. When it is bright out, the light hitting the resistor lowers its resistance and closes the circuit. When it gets dark and less light shines on them, the resistance increases until the circuit is opened (shut off) and electrons are no longer free to flow.

It is important to note that though the principle behind these types of sensors is fundamentally the same, sensors all offer their own degrees of sensitivity to light, so some are more suitable to lighter environments and some to darker locations.

What Are They Used For?

That’s all well and good, scientifically, because that’s how a photocell sensor works. But what does this mean on a practical level? What are the uses of these devices as respects light and lighting?

Think of a situation wherein you would need to control the usage of energy, remotely and passively. A situation wherein you would need light at certain times, generally at certain times of the day, but not at others.

Think of streetlights and security lights that don’t have the types of switches to which most consumers are used. These types of lights need to be controlled remotely, and sometimes due to energy efficiency concerns, they need to be controlled passively as well. Therefore, these types of devices employ the use of a photocell sensor to operate them.

They actually have a lot of different uses, but think of it this way. If a sensor of this nature was built into the circuit that controlled the operation of a streetlight, for example, it would enable the streetlight to be switched into operation as soon as it was dark out. This enables streetlights to draw power only when needed and shut off the power when not needed. It also makes it practical for them to work during odd hours of the day when it gets suddenly dark, such as during storms, for example.

That is the basic purpose of most photocell sensors, which are fairly simple but have very important economic value. Check out our collection of these types of sensors at the link above.

Give Us A Call

If this simplified explanation of what a photocell sensor was not detailed enough and you would like some more specific information on the way they work and how they are put to use, don’t hesitate to reach out to our team at 1-888-988-2852. We’d be more than happy to clear up any confusion on the matter, to go over product details, or just to help you settle on the lighting, fixtures, and accessories for which you might have a need. Investigate our collection of sensors, and if you have any questions at all, give us a shout.