Why Do Photocells Face North?

Have you ever wondered why photocells face north? Photocells are popular nowadays and more people are choosing to add photocells into their lighting fixtures. There are many benefits that you can get from photocells. However, proper placement is required so that it will work efficiently. This makes one wonder why they should face north. Let us find out the answer to this question below.

Why do photocells face north? One of the reasons why photocells face north is that it provides them with a balanced on and off schedule due to the arc of the sun. A photocell that faces east and has a clear view in all directions will turn the lights on and off early. On the other hand, a photocell that faces west will turn lights on and off late. If you want to install the photocell on the south side, make sure to face it west, east, or to the ground.

Photocells are used to control a light fixture. It is usually used in outdoor security lighting. Photocells automatically illuminate the fixture at night and turn off in daylight. On the other hand, photocells will not work properly unless they are placed in the proper direction. Read the rest of the article to learn more about the topic.

Why do photocells face north
Image by Florian Kurz from Pixabay

Why is Photocell Placement Important?

Photocell placement is important because if it is not placed properly, it will not operate. The main purpose of a photocell is to control lighting systems so that they automatically illuminate the surroundings at night. Avoid placing the photocells in a sheltered or shaded area. It is recommended that you place the photocell in a direction where it faces north and away from sunlight. Moreover, see to it that there are no artificial lights that surround it at night.

Should You Point Photocells South?

If you are located in the northern hemisphere, it is ideal that you should not place the photocells facing south. The reason for this is how the sun arcs. Take note that photocells that face south are exposed to direct sunlight. On the other hand, if they face north, they can be able to detect light without direct sunlight. It is important that you do not expose photocells to direct sunlight because it can burn out the components and damage the photocell.

Should Photocells Face North?

Photocells should face north. Make sure that you place it strategically so that you can get the best control for your light fixture. If you are placing the photocell outdoor, do not face it south because it will pick up the excessive sun that can diminish its effectiveness. If you cannot place the photocell north, you can place it west or east. You can also check out this article titled, are all photocells the same? We have shared tips and ideas that you can refer to.

Where to Place a Photocell?

Photocells are usually placed between six to eight feet of the window area. It should be located centrally to the area that is illuminated by the electrical lighting. Make sure to mount the photocell so that it faces a reflected light and not direct lighting. You can also check out this article that we have written that discusses if a photocell will work in the shade. We have shared tips and ideas that you can refer to.

Where to Place Photocells at Night?

At night, make sure not to place the photocells in a direction where they face artificial light sources like streetlamps. This should be avoided because the artificial light will deceive the photocell and it will turn off because it will sense the artificial light as daylight. Photocells should also not be placed near light reflections because it can cause the light to repeatedly turn on and off.

What are the Features of a Photocell?

A photocell is an electronic component that is a resistor. The resistive value of the photocell changes when light passes across the surface electrodes. Take note that the resistance of the photocell lessens as more light pass across it. When placed in an area that is completely dark, the photocell displays a high resistive value of about 10 megaohms. This enables the photocell component to control the light fixture. We have also shared this article that discusses why dusk to dawn light stays on all day. We have shared helpful tips and ideas that you can refer to.

✅ Video – Photoelectric Cells and Their Applications

Physics4students shared the video below on YouTube. It discusses what photoelectric cells are and their applications. A photoelectric cell is a device that converts light energy into electrical energy. Watch the video to learn more about the different types of photoelectric cells.

Are Photocells Adjustable?

Some photocell sensors are adjustable. This is great because it allows the user to choose the light level that will activate the semiconductor. At night, the flow stops, and the light switches on. Because photocells sense the level of light, they will automatically adjust to changes and they are also not affected by daylight-savings time. Hence, photocells are a maintenance-free and energy-efficient addition to your outdoor lighting. You can also check out this article that discusses what causes a photocell to go bad. We have shared an in-depth discussion about the topic.

How to Replace a Lamp Post Photocell

To replace a lamp post photocell, you need to deal with some wiring. This can be a delicate task especially for those who are not that familiar with electrical wiring. You can always hire the services of a professional to handle the task. If your lamp post does not turn on at night, you need to check the bulb. If that does not solve the problem or the light flickers, then the issue might be a bad photocell.

Where Else to Use Photocells?

Photocells are usually used in sound reproduction, exposure meters, burglar alarms, robotics, and automatic lights. Moreover, photocells can also be used as sensors and switches. Photocells are also commonly used as timers to measure the speeds of runners in a race. Aside from that, it can be used as an alternative to variable resistors and photovoltaic cells. Let us learn more about the different uses of photocells below.

Burglar Alarm

Photocells are also used in burglar alarms which are a device that is used as safety against thieves. Burglar alarms are usually used to detect intruders and to keep track of them as well. A photocell and an infrared light source make up a burglar alarm. When the light that comes from the infrared source falls on the photocell, it creates a constant photoelectric effect. Moreover, any deviation in the direction of the infrared light will cut off the light that falls on the photocell. This leads to a no-flow photoelectric effect that activates the relay circuit to sound the siren and alert the household of the intruder.

Sound Reproduction

A common use of photocell is in sound reproduction, especially in movies. With the use of a slim translucent strip, the sound is recorded in the film. This strip is called the soundtrack. How transparent the soundtrack will have to depend on the change in the frequency level of the recorded sound. The projector light of the soundtrack gets in contact with the photocell as the film is projected.  The change in the level of soundtrack changes the intensity of the sound which results in a varied photo-electric current. As a result, the electric current is amplified and directed into speakers.

Exposure Meter

Photocells are also used in exposure meters which are an instrument that is designed with the camera to determine the right time of exposure of the film which is necessary for taking good pictures. The perfect picture requires minimal film exposure when there is high-intensity light and vice-versa. A photocell, connected batteries, and milliammeter are required to construct an exposure mete.

Take note that there is a direct proportion between the light intensity and the photoelectric current that is developed in the cell. In case there is less deflection on the milliammeter, the photoelectric current is also lesser. If there is minimal light intensity, there is maximum exposure. Moreover, if there is more milliammeter deflection, there is also more photoelectric current. This results in high light intensity so that there is minimal exposure.

Where to Mount a Photocell?

It is recommended that you mount the photocell between six to eight feet in the window area. It should be at the center of the area that is illuminated by the electrical lighting that needs to be controlled. See to it that it is mounted in an area where it faces reflected light and not direct light.

How Much Light Does a Photocell Need?

Photocells are usually sensitive to light between 700nm and 500nm light. Photocells are the common CdS cells that are available on the market are not that sensitive to all types of light. You can also read this article that we have shared titled, how does a dusk to dawn photocell work? We have shared an in-depth discussion about the topic.

What do Photocells Do?

Photocells act as sensors that are attached to the lighting fixtures. It automatically turns off the light in daylight and turns it off at night. Photocells work on semiconductor photoconductivity which means that the energy of photons that hits the semiconductor frees electrons to flow. As a result, it decreases the resistance.


In this article, we have discussed why photocells face north. We have found out that it is ideal to place photocells facing north because it provides them with a balanced on and off schedule. If you are planning to use photocells outdoors, make sure that you place them properly so that it operates efficiently. Thank you for reading!

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