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Seeed Light Sensor Selection Guide

Here at Seeed, we have released different Light Sensors and this may cause problems for some of you where you don't know which one to pick and which one is suitable for your needs. Here comes the solution! Please check the comparison in this site for more reference.

For all the Light sensors in our bazaar, please click Bazaar Light tag to check.

What is Light Sensor

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 then just its definition. It comes in different types, used in various applications and more!

Glossary of terms

Before we start with today’s’ light sensor guide, we’ll have to understand the following terms that are commonly associated with light. I’ve simplified it for easier understanding:

Candela

  • Originated from the term candles, candela refers to luminous intensity; how strong is the light to a naked eye

  • The higher the luminous intensity, the higher the sensitivity it is to our eyes

Lumen

  • Measures the total amount of visible light from a light source through the relationship between luminous intensity and the angle that a light beam fills
  • Commonly used to rate the brightness of a light bulb
  • To simply put it Lumen = Total amount of light emitted in all directions

Lux

  • Used to measure illuminance, the area where the luminous flux is spread
  • It’s similar to Lumen but it takes into account the surface area
  • To simply put it, Lux = total amount of light that falls on a particular surface

Note

If you’re still confused between Lumen and Lux, here’s a graphical representation:

Reference: Lux vs Lumen

What are the types of light sensor

There are different types of light sensors available; mainly Photoresistor, Photodiodes, and Phototransistors. Sounds technical? I’ll break it down with the explanations below!

1. Photoresistors (LDR)

The most common light sensor type that’s used in a light sensor circuit are photoresistors, also known as a light-dependent resistor (LDR). Photoresistors are used to simply detect whether a light is on or off and compare relative light levels throughout a day.

What are photoresistors made of?

  • A high resistance Semiconductor material called cadmium sulfide cells, highly sensitive to visible and near-infrared light

How photoresistors work?

As its name suggests, photoresistors work similarly to your regular resistors, but instead resistance change is dependent on the amount of light it’s exposed to.

  • High intensity of light causes a lower resistance between the cadmium sulfide cell
  • The low intensity of light results in a higher resistance between the cadmium sulfide cells

This working principle can be seen in applications such as street lamps, wherein the day, the higher light intensity results in lower resistance and no light produced.

2. Photodiodes

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.

Also known as a photodetector, photo sensor.

What are photodiodes made of?

  • Photodiodes are mainly made from silicon and germanium materials and comprise of optical filters, built-in lenses and surface areas

How photodiodes work?

Photodiodes work on the working principle called the inner photoelectric effect. To simply put it, when a beam of light hits, electrons are loosened, causing electron-holes which results in electrical current to flow through.

  • The brighter the light present, the stronger the electrical current will be.

Photodiode light sensor applications

Since current generated by photodiodes are directly proportional to the intensity of light, it makes it favorable for light sensing that requires fast light response changes.

Since photodiodes are responsive to infrared light, it’s applicable for more usages as well.

Here are some of the applications of photodiode:

  • Consumer electronics ranging from compact disc players to smoke detectors and even remote control devices
  • Medical applications such as equipment/instruments used for measuring and analysis purposes
  • Solar energy systems such as solar panels

3. Phototransistors

The 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 doesn’t fair better in low light level detection as compared to photodiodes. Since both light sensor types share a similar working principle, do refer to the previous explanation!

Light Sensors at Seeed

Which One is Best For You

Product Grove - Light Sensor v1.1 Grove - Light Sensor v1.2 Grove - Digital Light Sensor Grove - Sunlight Sensor Grove - I2C UV Sensor (VEML6070) Grove - Light&Color&Proximity Sensor
Thumbnail
Interface Analog Analog Digital I2C I2C I2C
Peak Wavelength 540nm 540nm / 280-950nm 320-410 nm /
Operating Temperature -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -40°C to 85°C -30~85°C
Max. Lux [klx] / / 0.1 - 40,000 LUX / / /
UVA Sensitivity / / / / 5 μW/cm2/step(typical) 60

Quick Insight

Low-cost option: Grove – Light Sensor v1.2

Starting off the list of light sensors available right here at Seeed is the Grove – Light Sensor v1.2! Alongside its low price tag of $2.90, 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 of connecting jumper wires and soldering it on!

Its features include:

  • Dual OpAmp chip LM358 on board
  • Analog module
  • Onboard grove port for easy interfacing
  • Convertable electrical signal output
  • Depends on the ADC on your controller board, E.g. it can output 0-255 for an 8-bit ADC)
  • Small form factor
  • Recognize wider spectrum

Digital signal output option: Grove – Digital Light Sensor

If 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 3 modes to take your reading!

These three modes are infrared mode, full-spectrum, and human visible mode The human visible mode gives you reading close to your eye feelings

Its features include:

  • Wide dynamic range: 0.1 – 40,000 LUX
  • Wide operating temperature range: -40deg to 85deg
  • High-resolution 16-Bit digital output at 400 kHz I2C Fast-Mode
  • Programmable interrupt function with User-Defined Upper and lower threshold settings
  • Selectable detection modes

Sunlight detection option: Grove – Sunlight Sensor

Though it’s Made for direct sunlight detection with UV, this digital light sensor is suitable for a variety of other light sources as well, including visible and infrared light.

Based on the SI1145 sensor from SiLabs, it’s a low-powered, reflectance-based, infrared proximity, UV index and ambient light sensor with an I2C digital interface and programmable-event interrupt output.

Since performance is key, this light sensor offers a wide dynamic and spectrum detection range to top it all off!

Its Features Include:

  • Digital light sensor
  • Wide spectrum detection range
  • Programmable configuration
  • 3.⅗V Supply
  • Detect sunlight directly
  • Grove compatible
  • I2C Interface(7-bit)

Application Ideas

  • Light measurement
  • Light detector
  • Light-controlled switch
  • Smart home device
  • Ambient light sensing
  • Backlight control for display panel
  • Keyboard illumination control

Useful Projects

Grove - Introduction in a Light Sensor:

The Environment Cube! Know the Land Beneath You using Sigfox: A cube with all the necessary sensors, suitable for a wide range of applications like agriculture, monitoring, ,etc.

Seeed LoRa IoTea Solution: An automatic information collection system applied to tea plantation. It is part of intelligent agricultural information collection.

Intel Edison IoT Hydroponic Controller: An IoT enabled Hydroponics Controller using the Intel Edison during the Boston IoT Hackathon.

COI - Light Transmission Meter: The finished product uses the light sensor provided in the Grove Starter Kit Plus to measure change in light intensity.

The Environment Cube! Know the Land Beneath You! A cube with all the necessary sensors, suitable for a wide range of applications like agriculture. Know the land beneath you!

Resource

Tutorials on Grove - Light Sensor v1.1

Tech Support

Please submit any technical issue into our forum.