A light sensor is a photoelectric device that converts light energy (photons) detected to electrical energy (electrons). Seems simple? There is more to a light sensor than just its definition. It comes in different types and is used in various applications! Hence, in today’s light sensor guide, we’ll be exploring all you need to know about light sensors: Before starting today’s light sensor guide, we’ll have to understand the following terms commonly associated with light. I’ve simplified it for easier understanding: If you’re still confused between Lumen and Lux, here’s a graphical representation: Understood the terms? Let’s now get started! Different types of light sensors are available, mainly Photoresistors, Photodiodes, and Phototransistors. Sounds technical? I’ll break it down with the
explanations below! The most common light sensor type used in a light sensor circuit are photoresistors, also known as Light-Dependent Resistors (LDR). Photoresistors detect whether a light is on or off and compare the relative light levels throughout the day. Photoresistors are made of highly-resistance semiconductor material called cadmium sulfide cell, which is highly sensitive to visible and near-infrared light. As its name suggests, photoresistors work similarly to your regular resistors, but the resistance change depends on the amount of light it is exposed to. High light intensity will cause a lower resistance between the cadmium sulfide cell, while low light intensity results in a higher resistance between the cadmium sulfide cells. This working principle can be seen in applications such as street lamps, wherein during the day, the high light intensity
results in lower resistance, and thus they are not lit up when the sun is still shining brightly. Photodiodes are another type of light sensor. But instead of using the change in resistance like LDR, it’s more complex to light, easily changing light into a flow of electric currents. It is also commonly known as a photodetector or photo sensor. Photodiodes are mainly made
from silicon and germanium materials and comprise optical filters, built-in lenses, and surface areas. How do Photodiodes Work?Photodiodes work on the working principle called the inner photoelectric effect. When a beam of light hits, electrons are loosened, causing electron holes that result in the electrical current flowing through. The brighter the light, the stronger the electrical current will be. Photodiode Light Sensor ApplicationsSince the current generated by photodiodes is directly proportional to light intensity, it makes it favorable for light sensing that requires fast light response changes. Also, they are very responsive to infrared light, thus more projects can be done in that field. Here are some of the applications of photodiode:
3. PhototransistorsThe last light sensor type we’ll be exploring today is the phototransistor. The phototransistor light sensor can be described as a photodiode + amplifier. With the added amplification, light sensitivity is far better on the phototransistors. However, it does not fair better in low-light detection than in photodiodes. Since both light sensor types share a similar working principle, do refer to the previous explanation! Light Sensor ApplicationsConsumer ElectronicsEver wonder what’s behind your smartphone and tablets that allow for auto-screen brightness adjustments? Yes, it’s an ambient light sensor! It measures the ambient light level of your surroundings and determines the suitable brightness of your screen so that your eyes won’t hurt in the dark and you can read messages under the scorching sun! AutomobilesSimilar to how light sensor works on smartphones, it is used in automobiles to support the driver’s field of vision. The present light sensor detects surrounding ambient light, and if it’s getting too dark, it’ll automatically turn on the light systems. It is very helpful when you enter a tunnel or when it starts to rain! Agricultural UsagesWe all know crops need mainly two things for growth; sunlight and water. This is where a light sensor comes to play, helping farmers keep their crops hydrated yet not overhydrating them. Here’s how:
Security ApplicationsLight sensors are connected to circuits and placed inside the cargo during shipments. They can detect whenever a container is accidentally opened, as there will be a change in light exposure. This helps to decrease lost goods and damages. Photoresistors are commonly used in this case. Light Sensors Available at SeeedSince photoresistors, photodiodes, and phototransistors offer versatility at affordable pricing, you can collect illuminance data using Arduino or Raspberry Pi through our selection of light sensors available at Seeed! Low-Cost Option: Grove – Light Sensor v1.2Starting off the list of light sensors available here at Seeed is the Grove – Light Sensor v1.2! Alongside its low price tag of $3.20 comes a highly sensitive and reliable photodiode for your light-sensing needs! Easily parable with your Arduino board through our Grove plug-and-play system, you’ll save yourself some trouble connecting jumper wires and soldering them on! Features:
Phototransistor Option: Grove – Light Sensor (P) v1.1Need a light sensor that uses a phototransistor instead of the traditional light-dependent resistor (LDR)? This option is for you! Similar to the earlier Grove – Light Sensor v1.2, this light sensor is priced at $3.20! Packed with an LS06-S phototransistor, this light sensor module has a much more linear analog output conforming to illuminance, ranging from 0 to the supplying voltage of normally 5V. Features:
Digital Signal Output Option: Grove – Digital Light SensorIf you’re looking for a digital signal output option alongside a selectable light spectrum range, the Grove – Digital Light Sensor is the one for you! Based on the I2C light-to-digital converter TSL2561 that does the digital signal outputting, this light sensor module features dual light-sensitive diodes, where you can switch between three modes to take your reading! These modes are the infrared mode, full-spectrum, and human visible mode. Features:
Sunlight Detection Option: Grove – Sunlight SensorThis sunlight sensor is based on the SI1145, a low-powered, reflectance-based, infrared proximity, UV index, and ambient light sensor with an I2C digital interface and programmable-event interrupt output. Features:
Smart Light Sensor Option: Grove – Heelight SensorPerhaps the most interesting light sensor option on this list is the Grove – Heelight Sensor! Unlike any other light sensor on this list, this only does contactless light control through voice recognition. Based on heelight, a smart colorful bulb controlled by digital sound waves, this sensor does not require any Bluetooth, WiFi, or ZigBee! However, do note that this sensor only recognizes digital voices. If you need human voice recognition, try the Grove – Speech Recognizer. Features:
How to use a Light Sensor with Arduino?We’ve gone through the theoretical side of light sensors, now it is time for our light sensor with Arduino tutorial. For today’s tutorial, we’ll use the Grove – Light Sensor v1.2 module and an LED bar to build a simple circuit that changes based on the light! Here’s What You Need:Seeeduino V4.2Grove Base Shield Grove – Light SensorGrove – LED BarHardware connections:
It should look something like this after the above steps: Software configurations with Arduino Code
If you would like a video tutorial on the above light sensor, you may refer to this instead:
Resources and Going FurtherLight Sensor Projects:Want to go further than just building a light sensor circuit with LED? Try this list of light sensor projects available on our hackster.io page!
Product Resources:For Grove – Light Sensor v1.2 and Grove – Light Sensor (P) v1.1
For documents on the three other light sensor recommendations, you can visit their respective product pages. SummaryThat’s all for today on light sensors. I hope with today’s blog, you get a deeper understanding of what it is, how it works, its usages, and what it takes to build one with an Arduino. To help you easily get started, consider the list of touch sensors I’ve recommended, and hopefully, you will try out your very own light sensor projects today! Continue ReadingWhich type of sensor is most likely to be used in seismology applications?For seismology applications, an accelerometer is used to record seismic signals, performing as a seismometer.
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