EYE ON NPI - Melexis' MLX90632 Miniature Far Infrared (FIR) Sensors

Adafruit Industries

This week's EYE ON NPI is going to keep an eye on the hot summer temperatures - it's Melexis' MLX90632 Miniature Far Infrared (FIR) Sensors (https://www.digikey.com/en/product-highlight/m/melexis/mlx90632-miniature-far-infared-fir-sensors) a series of low cost, high performance, ultra tiny IR temperature sensors with medical grade accuracy! The MLX90632 comes from Melexis (https://www.digikey.com/short/zvzvp01b) whose expertise is IR temperature sensors. We've been using their sensors like the MLX90614 (https://www.digikey.com/short/b990pn8w) for over a decade! These sensors are specifically good for sensing the temperature of something that they are not touching. There's lots of reasons to use this, for example when something is really hot, so you don't want your circuit to reach the same temperature which would degrade or damage it. Or for sanitation: unlike in-ear or oral temperature sensing, you can point this at someone's head or mouth to measure their temperature without ickyness. Or maybe you're measuring something that is far away or hard to attach a thermocouple to, for example to measure the temperature of a leaf for calculating the Vapor Pressure Deficit (https://en.wikipedia.org/wiki/Vapour-pressure_deficit). For 'single point' measurement, we've used the MLX90614 (https://www.digikey.com/short/b990pn8w), they've also got the MLX90640 (https://www.digikey.com/short/8pf5zrq8) which is more like a camera, with 32x24 pixel IR camera support. Both are way cheaper than a full FLIR camera module, and we love the I2C interface which makes it easy to interface with any microcontroller or microcomputer. However, what we really wanted is something more affordable and hopefully even surface-mount-friendly. After a bit of searching this week we bumped into the MLX90632 (https://www.digikey.com/short/zvzvp01b) which has everything we've wanted! First up, unlike the other IR sensors we've used, the MLX90632 (https://www.digikey.com/short/zvzvp01b) is compact and surface mountable - that makes assembly fast and easy without hand soldering and lead-clipping. Second, it's got an I2C interface so we don't have to do any analog noodling to convert a current to temperature. It's also pre-calibrated so you can use it right 'out of the box' like classic non-IR temperature sensors. There's versions for both 3.3V or 1.8V power/logic, so you can pop it into your circuit with ease. And if you're using for human/animal temperature monitoring, the medical-grade version is factory calibrated with an accuracy of ±0.2˚C within the narrow object temperature range from 35 to 42˚C. Note that both 'standard' and 'medical' grade have different accuracy zones, and as you get to the extremes from 25C, the accuracy in C will rise to +-4C: its a trade-off between range and accuracy. Just note that you need to tell the sensor which mode you want to be in, over I2C Speaking of - this sensor is I2C compatible! So it's easy to interface this using C, Arduino, Python, etc. Check out the register map in the datasheet - you will need to read the pre-programmed calibration constants in order to convert readings to ambient/remote temperatures. There's also built in EEPROM that you can program with offsets or to change the I2C peripheral address, handy if you have device-specific settings that you want to tie to the individual sensor for custom calibration. To make it easier to get going, check out the Melexis C library on github (https://github.com/melexis/mlx90632-library) If you think the MLX90632 (https://www.digikey.com/short/zvzvp01b) is hot-to-trot, then you are in luck because there's tons in stock at DigiKey right now, available for immediate shipment! Order today and you'll get this tiny IR sensor for your own by tomorrow afternoon so you can start getting precision remote temperature sensing added to your design in a jiffy.