Hands down, light sensors are a treasure trove. Looking into how these scientific wonders work allows us to deploy them with higher operational efficiency. In the process, you become effective enough to expand your world like never before.
The truth of the matter is we don’t just need light. Rather, we need ample light.
Too much heat from the sun can scorch our skin, and if unchecked may even cause skin cancer. And yet, too little sun in our lives can also lead to health complications. Having the right amount of light is, therefore, paramount.
This is where light sensors come in handy. They save us the trouble of guessing by determining how intense light is within our surroundings.
In this post, we’ll walk you through how all that happens and how such a wonderful instrument as a light sensor has helped countless people before you—with great benefit. Read on.
How Light Sensors Work
By definition, a light sensor is a photoelectric instrument that gauges the amount of light (or light intensity) in a given area. Essentially, the device does this by converting light energy (photons) into electrical energy.
The Science Behind Light Sensors
At its very core, light sensors rely on the photoelectric effect. It’s simple really.
The photoelectric effect states that electromagnetic radiation (such as light) can cause electrons in a metal to get excited when bombarded
As electrons in the metal get excited, electrical activity is produced. The stronger the amount of incident light, the greater the electrical output.
Image 1: Electrons in a metal plate getting excited when hit by light energy.
Now, to be able to measure light intensity, we must be able to quantify light energy. And today, there are three ways to do just that:
| Unit of Measurement | Definition | Symbol |
|---|---|---|
|
1.Candela |
Luminous intensity equivalent to one candle. | cd |
|
2.Lux |
The total amount of light that falls on a surface of 1 square meter. | lx |
|
3.Lumen |
The total amount of light emitted in all directions by a light source. (e.g., lamp) | lm |
Table 1: Ways to Measure Light Intensity
For instance, a flashlight that could generate 1 cd (candela) of light intensity may have 12.5 lm (lumen) of luminous intensity in all directions. But if you cover half of its lamp, said flashlight will still maintain a 1 cd light intensity but will have only 6.25 lm—half of its original luminous intensity.
On the other hand, the amount of light said flashlight generates on a table nearby can be measured in lux. Another term for this is illuminance.
Light Sensor Types
Basically, there are two main light sensor types. Though both react to the presence of light, one uses the amount of electric current produced while the other relies on electrical resistance to measure illuminance.
1. Photodiode
2. Photoresistor
Another common light sensor type is the phototransistor. However, it’s essentially a photodiode on steroids—armed with greater capabilities. Although it’s much more complex in design, phototransistors operate much like photodiodes.
Most Common Applications of Light Sensors
Our ability to measure the intensity of light allows us to deploy just the right amount of light. In this regard, light sensors play a huge role in expanding our world by showing us illuminance. Below are some of the most common ones:
Photography
There may not be work that’s more reliant on proper lighting than photography. With light meters, photographers can determine incident light on a subject or reflective light on a background. Doing so allows them to adjust lighting accordingly, not to mention choose the most spot-on shutter speed and f/stop.
Engineering & Construction
Engineers and architects can make the most of light meters to determine the best window or lighting placement. On your end, you can use the device to choose the best lighting fixture for home improvement.
Consumer Electronics
Light sensors are central to how smart devices operate. You may be wondering how your smartphone detects motion. And the answer lies in these devices using light sensors such as phototransistors, measuring the presence of light or lack of it to adjust accordingly.
For Security Purposes
It’s surprising but light sensors are central to the function of a smoke detector. Placed at a certain angle inside the smoke detector chambers, a light sensor detects when the light from an LED is disrupted (presence of smoke). This way, these amazing devices are your first line of defense.
Public Spaces
With inadequate lighting in a public space (e.g., parks, streets, highways), you invite disaster. A car park that’s dimly lit will encourage criminals to operate endangering people’s lives and properties in the process.
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Light sensors can play their part by ensuring adequate lighting for everyone’s safety.