# Adafruit LTR390 UV Sensor ## Overview ![](https://cdn-learn.adafruit.com/assets/assets/000/098/162/medium800/adafruit_products_iso.jpg?1609265047) The [LTR390](https://www.adafruit.com/product/4831) is one of the few low-cost UV sensors available, and it's a pretty nice one! With both ambient light and UVA sensing with a peak spectral response between 300 and 350nm. You can use it for measuring  how much sun you can get before needing to covering up. ![](https://cdn-learn.adafruit.com/assets/assets/000/098/172/medium800/adafruit_products_LTR390_top_header.jpg?1609268349) Unlike sensors that estimate UV Index readings from visible and IR light levels such as the [Si1145](https://www.adafruit.com/products/1777), the LTR390 incorporates two sensors, one for visible and another specifically designed to measure UV light levels. The sensor's CircuitPython library includes routines to derive the UV Index value from raw UV measurements as well as calculating the ambient light Lux level. The LTR390 also has a much much simpler I2C interface so you can run it on the Arduino or Python microcontrollers/microcomputers with ease. Unlike the [GUVA analog sensor](https://www.adafruit.com/products/1918), the biasing and ADC is all internal so you don't need an ADC. ![](https://cdn-learn.adafruit.com/assets/assets/000/098/173/medium800/adafruit_products_LTR390_STEMMA_side.jpg?1609268360) To make using it as easy as possible, we’ve put the LTR390 on a breakout PCB  in our [Stemma QT form factor](https://www.adafruit.com/?q=Stemma+QT+Sensor) with a sprinkle of support circuitry to give you options when testing. You can either use a breadboard or the[** SparkFun qwiic**](https://www.sparkfun.com/qwiic) compatible [**STEMMA QT**](https://learn.adafruit.com/introducing-adafruit-stemma-qt) connectors, and compatibility with 5V voltage levels as commonly found on [Arduinos](https://www.adafruit.com/category/17), as well as 3.3V logic used by many other boards like the Raspberry Pi or our Feathers. ** ** [**QT Cable is not included** , but we have a variety in the shop](https://www.adafruit.com/?q=stemma+qt+cable&sort=BestMatch) for quick plug-and-play support ![](https://cdn-learn.adafruit.com/assets/assets/000/098/174/medium800/adafruit_products_LTR390_back.jpg?1609268370) - [Next Page](https://learn.adafruit.com/adafruit-ltr390-uv-sensor/pinouts-2.md) ## Featured Products ### Adafruit LTR390 UV Light Sensor - STEMMA QT / Qwiic [Adafruit LTR390 UV Light Sensor - STEMMA QT / Qwiic](https://www.adafruit.com/product/4831) The LTR390 is one of the few low-cost UV sensors available, and it's a pretty nice one! With both ambient light and UVA sensing with a peak spectral response between 300 and 350nm. You can use it for measuring  how much sun you can get before needing to covering up. Unlike the... In Stock [Buy Now](https://www.adafruit.com/product/4831) [Related Guides to the Product](https://learn.adafruit.com/products/4831/guides) ### STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable [STEMMA QT / Qwiic JST SH 4-pin to Premium Male Headers Cable](https://www.adafruit.com/product/4209) This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium Dupont male headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert... In Stock [Buy Now](https://www.adafruit.com/product/4209) [Related Guides to the Product](https://learn.adafruit.com/products/4209/guides) ### JST SH 4-pin Cable with Alligator Clips - STEMMA QT / Qwiic [JST SH 4-pin Cable with Alligator Clips - STEMMA QT / Qwiic](https://www.adafruit.com/product/4398) This cable will make it super easy to use our plug-and-play STEMMA QT boards with boards like Circuit Playground. On one end you get a Qwiic / STEMMA QT connector (technically known as a JST SH 4-pin plug)  into 4 individual wires with grippy alligator clips. We're carrying these to... Out of Stock [Buy Now](https://www.adafruit.com/product/4398) [Related Guides to the Product](https://learn.adafruit.com/products/4398/guides) ### 4-pin JST PH to JST SH Cable - STEMMA to QT / Qwiic [4-pin JST PH to JST SH Cable - STEMMA to QT / Qwiic](https://www.adafruit.com/product/4424) Are you a maker in the midst of a [**STEMMA**](https://learn.adafruit.com/introducing-adafruit-stemma-qt/what-is-stemma) dilemma? This 200mm long 4-wire cable is a fantastic chimera-cable fitted with **STEMMA QT / Sparkfun Qwiic JST SH** on one end,... In Stock [Buy Now](https://www.adafruit.com/product/4424) [Related Guides to the Product](https://learn.adafruit.com/products/4424/guides) ### STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets [STEMMA QT / Qwiic JST SH 4-pin Cable with Premium Female Sockets](https://www.adafruit.com/product/4397) This 4-wire cable is a little over 150mm / 6" long and fitted with JST-SH female 4-pin connectors on one end and premium female headers on the other. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and... In Stock [Buy Now](https://www.adafruit.com/product/4397) [Related Guides to the Product](https://learn.adafruit.com/products/4397/guides) ### STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long [STEMMA QT / Qwiic JST SH 4-pin Cable - 100mm Long](https://www.adafruit.com/product/4210) This 4-wire cable is a little over 100mm / 4" long and fitted with JST-SH female 4-pin connectors on both ends. Compared with the chunkier JST-PH these are 1mm pitch instead of 2mm, but still have a nice latching feel, while being easy to insert and remove. In Stock [Buy Now](https://www.adafruit.com/product/4210) [Related Guides to the Product](https://learn.adafruit.com/products/4210/guides) ## Related Guides - [Adafruit Pixel Trinkey](https://learn.adafruit.com/adafruit-pixel-trinkey.md) - [Adafruit CH334F Mini USB Hub Breakouts](https://learn.adafruit.com/adafruit-ch334f-mini-4-port-usb-hub-breakout.md) - [Adafruit RS232 Pal](https://learn.adafruit.com/adafruit-rs232-pal.md) - [Adafruit Data Logger Shield](https://learn.adafruit.com/adafruit-data-logger-shield.md) - [Integrating Color Sensors with itsaSNAP and HomeKit](https://learn.adafruit.com/integrating-color-sensors-with-itsasnap-and-homekit.md) - [Adafruit TB6612 1.2A DC/Stepper Motor Driver Breakout Board](https://learn.adafruit.com/adafruit-tb6612-h-bridge-dc-stepper-motor-driver-breakout.md) - [Adafruit RS-232 Full Pinout Level-Shifter Breakout](https://learn.adafruit.com/adafruit-rs-232-full-pinout-level-shifter-breakout.md) - [Adafruit Motor Shield V2](https://learn.adafruit.com/adafruit-motor-shield-v2-for-arduino.md) - [Adjustable Breadboard Power Supply Kit](https://learn.adafruit.com/adjustable-breadboard-power-supply-kit.md) - [Adafruit Voice Bonnet](https://learn.adafruit.com/adafruit-voice-bonnet.md) - [Storage humidity and temperature monitor](https://learn.adafruit.com/storage-humidity-and-temperature-monitor.md) - [Adafruit PCA9546 4-Channel I2C Multiplexer](https://learn.adafruit.com/adafruit-pca9546-4-channel-i2c-multiplexer.md) - [Adafruit QT Py ESP32-C3 WiFi Dev Board](https://learn.adafruit.com/adafruit-qt-py-esp32-c3-wifi-dev-board.md) - [Color Sensing Music Player](https://learn.adafruit.com/color-sensing-music-player.md) - [Adafruit 4-Channel ADC Breakouts](https://learn.adafruit.com/adafruit-4-channel-adc-breakouts.md)