# micro:bit Lesson 4. Sensing Light ## Overview In this guide, you will learn how to sense the light level using a micro:bit.  By use of a clever bit of coding the micro:bit's display LEDs can be used to measure the light level, without the need for any extra hardware. However, this feature is only available when using the JavaScript blocks editor.  You can however attach a resistor and photoresistor to the micro:bit and use an analog input of the micro:bit to measure the light level. This has the advantage that once you know how to do this, you can attach other analog sensors to your micro:bit and make measurements with them. ![](https://cdn-learn.adafruit.com/assets/assets/000/051/034/medium800thumb/temperature___humidity_photoresistor.jpg?1518684353) - [Next Page](https://learn.adafruit.com/micro-bit-lesson-4-sensing-light-and-temperature/parts.md) ## Featured Products ### BBC micro:bit [BBC micro:bit](https://www.adafruit.com/product/3530) The British Invasion is here! No, not music...microcontrollers! New to the USA is the newest and _easiest_ way to learn programming and electronics - the **BBC micro:bit**. Designed specifically for kids and beginners, the  **micro:bit**  is a... No Longer Stocked [Buy Now](https://www.adafruit.com/product/3530) [Related Guides to the Product](https://learn.adafruit.com/products/3530/guides) ### BBC micro:bit Go Bundle [BBC micro:bit Go Bundle](https://www.adafruit.com/product/3362) Discontinued - [**you can grab** micro:bit v2 Go Bundle - Batteries and USB Cable Included **instead! **](https://www.adafruit.com/product/4834) The British Invasion is here! No, not music...microcontrollers! New to the USA is the newest and _easiest_ way to... No Longer Stocked [Buy Now](https://www.adafruit.com/product/3362) [Related Guides to the Product](https://learn.adafruit.com/products/3362/guides) ### Photo cell (CdS photoresistor) [Photo cell (CdS photoresistor)](https://www.adafruit.com/product/161) CdS cells are little light sensors. As the squiggly face is exposed to more light, the resistance goes down. When it's light, the resistance is about ~1KΩ, when dark it goes up to ~10KΩ. To use, connect one side of the photocell (either one, it's symmetric) to power... In Stock [Buy Now](https://www.adafruit.com/product/161) [Related Guides to the Product](https://learn.adafruit.com/products/161/guides) ### Small Alligator Clip to Male Jumper Wire Bundle - 6 Pieces [Small Alligator Clip to Male Jumper Wire Bundle - 6 Pieces](https://www.adafruit.com/product/3448) When working with unusual non-header-friendly surfaces, these handy cables will be your best friends! No longer will you have long, cumbersome strands of alligator clips. 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Out of Stock [Buy Now](https://www.adafruit.com/product/1008) [Related Guides to the Product](https://learn.adafruit.com/products/1008/guides) ## Related Guides - [RGB Matrix Portal Room CO2 Monitor](https://learn.adafruit.com/matrix-portal-room-co2-monitor.md) - [DIY Trinkey No-Soldering USB Air Quality Monitor](https://learn.adafruit.com/diy-trinkey-no-solder-air-quality-monitor.md) - [Temperature and Humidity Sensing in Home Assistant with CircuitPython](https://learn.adafruit.com/temperature-and-humidity-sensing-in-home-assistant-with-circuitpython.md) - [CircuitPython BLE Multi-Temperature Monitoring](https://learn.adafruit.com/circuitpython-multi-temperature-ble-monitoring.md) - [Adafruit AS7262 6-channel Visible Light Sensor](https://learn.adafruit.com/adafruit-as7262-6-channel-visible-light-sensor.md) - [Adabox 001 Temperature Alarm](https://learn.adafruit.com/adabox-001-temperature-alarm.md) - [Using Melexis MLX90614 Non-Contact Sensors](https://learn.adafruit.com/using-melexis-mlx90614-non-contact-sensors.md) - [AD8495 Analog Output K-Type Thermocouple Amplifier](https://learn.adafruit.com/ad8495-thermocouple-amplifier.md) - [Adafruit MLX90632 FIR Remote Thermal Temperature Sensor](https://learn.adafruit.com/adafruit-mlx90632-fir-remote-thermal-temperature-sensor.md) - [No-Code Indoor Grow Monitor with PPFD and VPD Measurements](https://learn.adafruit.com/no-code-indoor-grow-monitor.md) - [Introducing Adafruit CLUE](https://learn.adafruit.com/adafruit-clue.md) - [Monster M4sk Is Watching You](https://learn.adafruit.com/monster-m4sk-is-watching-you.md) - [Adafruit AMG8833 8x8 Thermal Camera Sensor](https://learn.adafruit.com/adafruit-amg8833-8x8-thermal-camera-sensor.md) - [Adafruit MCP9600 I2C Thermocouple Amplifier](https://learn.adafruit.com/adafruit-mcp9600-i2c-thermocouple-amplifier.md) - [Make an AI Freezer Monitor](https://learn.adafruit.com/ai-freezer-monitor.md)