How to Test a Photocell with a Multimeter

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Automatically controlling the lighting of your home saves both energy and money. Most individuals prefer timers to regulate their interior and exterior lighting. However, there is another alternative. This is where a photocell sensor comes in.

What is a Photocell Sensor?

In case you didn’t know, a photocell sensor is an electrical tool hooking up and communicating with a transformer. These sensors function like a timer switch in that they power light fixtures on and off automatically during a set “time.” 

They also function a bit differently than a timer switch, as these sensors detect the natural light of the sun for regulating artificial light output from lighting fixtures. 

How Does It Work? 

A photocell is composed of a semiconductor; the working of that is dependent on the incident light’s intensity. The semiconductor’s electrons are freed when the amount of lights goes beyond a specific frequency, and a photocell begins conducting. No electrons are freed every time the light is less, and the photocell does not conduct. 

The semiconductor used in a photocell is typical of a high resistance. That enables the photocell to prevent the flow of current when there’s no light. Whenever light falls on the photocell, it sends energy into the cell’s semiconductor part. Further, the frequency of incident light is proportional to the transferred energy. Thus, the more light, the more transmitted energy.

When that energy surpasses a specific level, the electrons of the semiconductor are freed, and the photocell begins conducting. That’s why a photocell conducts every time there’s a high light intensity subjected to it. 

A typical application of a photocell is the light-dependent resistor (LDR). These LDRs are utilized in energy-efficient lighting solutions, streetlights, and light sensors. Also, a photocell plays a very crucial role in effectively using daylight by turning off whenever natural light reaches a normal level. 

Like most outdoor landscape lights with low voltage lighting, photocell sensors inform the transformer to turn off and on based on the amount of light existing. For instance, the photocell sensor allows the transformer to know it’s time to turn the outdoor light fixture on when the sun sets outside, and it begins to get dark. 

Did you know that these sensors can also be utilized indoors in a place with windows? When there isn’t any natural sunlight coming through the window, the sensor powers on the indoor lighting fixtures. Such indoor photocell sensors decrease and increase the artificial light levels to save some energy.

For instance, the artificial light from your fixtures will rise on a cloudy day when natural light is not abundant. On the other hand, your artificial light source lowers when the sun is rising, and natural light is making its way into your room. 

How Do You Test a Photocell Sensor? 

Keep in mind that photocells are sensors allowing you to sense light. They are tiny, cheap, low power, simple to use, and do not wear out. The question now is, how do you test a photocell sensor? 

To check your photocell sensor, you need to use a digital multimeter. Follow the steps below to test your photocell sensor.

  1. Turn on your digital multimeter and set it on the resistance setting. Take note that resistance is normally indicated by the Greek letter omega. If your meter is not one of those auto-ranging, don’t worry. You can always change the knob to a high level like megaohms.
  1. Attach the red probe of your meter on one leg of your photocell while the black probe on the other leg. Its direction doesn’t matter, but you might need to utilize alligator clips to ensure the probes don’t slip from the leads of the photocell. 
  1. Protect the photocell, so no light falls on it. You can do that by putting your hand over it or by covering it. 
  1. Check your reading. It must be quite high. You may need to change the resistance setting down or up a notch to receive a reading. 
  1. Unbare the photocell. Change the knob on the digital multimeter by lowering the resistance setting. The resistance must read hundreds of ohms after a few seconds. 
  1. Do the same process by putting the photocell close to different light sources, like moonlight, sunlight, or a somewhat darkened room. Record the resistance each time. Take note that photocells might take from a few seconds to a few minutes to change when they’re eliminated from a light source then put into darkness. You might need to adjust the resistance settings to receive the correct readings as before. 

Should You Install a Photocell Sensor?

You will find different perks to install a photocell sensor. Some of these are the following:

  • Economical 

The light is turned on when it is dark. The best thing here is that you don’t need to remember to turn off the light on your own. The light is automatically turned off when dawn breaks the light or after there’s enough light from the rising sun.

That saves you from having to pay for unused power usage should you forget to turn off the light. That’s very practical if there’s a photocell sensor installed in your home. 

  • Security

The light can turn on its own after it is dark. That will be a big deterrent for any potential intruders.

  • Convenience

You don’t need to remember to switch off or on the light on your own. That’s because the photocell sensor will do the task on your behalf. Isn’t it amazing?  

Final Thoughts

A lot of people utilized photocell sensors for safety, convenience, and energy savings. Specialty for outdoor lighting, these sensors are an ideal deterrent for a burglar as they can power your lighting off and on when you are not home.

Hence, they are a convenience factor as you don’t need to think about forgetting to turn the lights off. Photocell sensors save energy, saving you money in the end. What’s more, indoor lighting with photocell sensors saves a huge amount of energy with the automatic reduction of artificial light.

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