How Do Solar Powered Motion Lights Work?

Solar-powered motion lights can seem like a hard puzzle to crack. How do they work, standing all inconspicuous, with no power lines attached yet turning on at the precise moment you show up?

Like magic! Of course, they are not magic, and though I would like to leave you to believe they are, I instead prefer that you know the means by which solar powered motion lights work.

Way back in my college days, my friends and I would try to beat the solar-powered motion lights installed just outside our dormitory.

We tried every trick imaginable, and yet the lights caught us every single time as we approached it, thwarting our carefully planned maneuvers over and over again.

Solar Powered Motion Lights Working Process

I remember being very impressed then, and at the same time, my curiosity was piqued, how could the lights turn on every time I approached it?

Why didn’t it work during the day? Was there a switch somewhere? Was the security monitoring camera and turning on the lights whenever I drew near the area?

Subsequently, my curiosity drove me to find out how “the freaky light” worked, and after learning how it worked, I became more impressed. It wasn’t anything I had guessed.

The “magic” of solar-powered motion lights is made possible by three major components: solar panels, motion sensors, and photocell sensors.

Understanding these components is crucial to grasp the means by which solar powered motion lights do what they do.

Solar Panels

Solar panels, all solar powered motion lights have them. Solar panels work by employing particles of light or photons provided by the sun to knock electrons free from atoms contained in the photovoltaic cells that make up the panel, subsequently generating a flow of electricity or direct current (DC).

Basically, a solar panel is made up of an array of connected photovoltaic cells that absorb energy from sunlight or daylight.

These photovoltaic cells convert the energy absorbed into electrical power, which is stored in rechargeable batteries contained in the solar-powered motion light device.

The solar-powered motion light then draws on this stored energy to give light when it is dark.

Solar panels are the reason why solar powered motion lights do not need to be connected to power lines; the energy is drawn from sunlight, provides all the electrical power required to get the lights running throughout the night.

Different solar panels are made from different variations of silicon and boast different efficiencies in storing up the electrical energy needed to power motion lights.

But most solar powered motion lights are outfitted with solar panels (and batteries) that keep the lights functional from dusk till dawn.

Motion sensors

Motion sensors are the “trick” behind the “magic” of motion lights, they tell the motion lights when there’s motion and keep watch to ensure that nothing creeps by a solar-powered motion lights installation, at night, without the exposure of light.

There are many types of motion sensors, contact, microwave, vibration, dual tech, passive infrared motion sensors are some of them.

Most, if not all, solar-powered motion lights you encounter, make use of passive infrared (PIR) motion sensors.

Passive infrared motion sensors work by detecting infrared waves. You can liken them to tiny eyes that detect heat waves radiated by moving objects (a person, bird, car, etc.).

This is the reason why you can never sneak up on a motion-sensing light.

Once activated, PIR motion sensors detect and monitor the infrared energy levels in the surrounding areas, casting a 180 degrees observative frame around a range of 10 – 40 meters (depending on the reach of the sensor).

Once a moving object passes through this range, it contributes its own wave of infrared energy to the surrounding, the passive infrared motion sensor picks up on the change in infrared energy levels and electronically turns on the lights.

Most motion sensing light setups would keep the light on for a preset amount of time, and then the detector shuts off the light unless it keeps sensing movement, in which case it would keep the light on for as long as the detected changes continue.

This way, motion lights are more frugal in their consumption of power than usual floodlights; they do not stay on all the time.

Thanks to the motion sensors, solar-powered motion lights can have batteries that only have the capacity to power the lights for 5 hours but still provide illumination from dusk to dawn, because the stored electrical power is only used when there’s motion, not all through the night like in usual floodlights.

However, it is possible for a moving object to stop within the range of a PIR motion sensor, and it would note that as an end to motion and turn off the lights till movement resumes.

Also, it is common for pets, flying birds, or junk carried by wind to trigger a PIR motion sensor.

Photocell sensors

You might have wondered why it is that solar powered motion lights do not work during the day. Though very active at night, once it’s a day, motion sensor lights cease to provide illumination when you pass by.

How does it know it’s the day? The answer is a simple little thing called photocell sensors. A photocell sensor tells the solar-powered motion lights when it’s the day.

A photocell sensor is a passive device that measures the radiant energy that exists in a very narrow range of frequencies in the light spectrum (infrared to ultraviolet) and uses the measure of radiant energy detected to generate electrical signals that indicate the intensity of light.

Simply put, a photocell sensor measures the ambient lighting in the area of the solar-powered motion light, and once it rises beyond a certain level, it triggers the lights to turn off.

In the same manner, when ambient lighting in the area drops below a certain level, it triggers the motion lights to turn on.

This makes the photocell an automatic switch that controls the activity of motion sensor lights, making it active only when it’s dark.

So, how do solar powered motion lights work?

Having discussed the three major components that enable solar powered motion lights to do what they do, and seeing how they do it, let’s put it all together and draw an answer.

A Solar-powered motion light draws on the energy found in the light of the sun to charge rechargeable batteries within the device. Using this energy it provides light at night.

Whenever an object passes through the “field of observation” of the passive infrared motion sensor, it turns on the light because it detects a change in infrared energy levels, a change caused by heat emitted by the moving object.

The solar-powered motion light keeps the light on for a preset amount of time once the detected motion ends and stays on throughout the period in which there’s motion observed.

A photocell sensor ensures that the solar-powered motion light works only during the night, by measuring the intensity of ambient light around the device.

This enables the device to store electrical energy during the day and supply light when it’s dark.

There you have it, that’s how solar powered motion lights work.