This weeks EYE on NPI is a sensor with a magnetic personality and we’re really attracted to it…You guessed it – we’re looking at the latest 3D magnetic field sensors from Melexis, the MLX90395.
These are some of the few high-magnetic-field sensors available, with up to +-120mT, that’s 1200 Gauss! Incredible when you consider many of our common magnetometers for IMU usage top out at +-50 Gauss. The sensor also has high precision, with 16-bit output and built in over-sampling since magnetometers can be a little noisy.
This sensor isn’t great for IMU usage — you’ll want to stick to ~1 Gauss ranges for detecting Earth-level fields. But it is excellent for magnetic field sensing such as that of a rare earth magnet.
These chips are often used for 3D motion sensing of an object, when it has a magnet embedded in it. Especially joysticks and other user controls, you get the environmental robustness of optical with the cost of mechanical. Plus you get Z axis motion, which optical doesn’t like as much. With a little bit of math you can detect various motions, positions, twists and distances, all without any mechanical wear.
The sensor is available in both 50 and 120mT ranges, and in a few packages. We happen to like the QFN because it’s pin-compatible with the earlier MLX90393. Note that it is not code-compatible with the ‘393.
For interfacing you can use I2C or SPI, with free-running or one-shot modes. There’s an interrupt pin for data ready checking, and a trigger pin if you want to trigger readings with GPIO rather than requesting over I2C/SPI.
We whipped up a driver over the weekend for people to use to get readings with an over-sample filter to help smooth out the readings.
It’s great to see revisions of sensors come out that give us better accuracy and precision, with wider ranges and lower prices and the MLX90395 does not disappoint. When ordering, check the last few digits of the product order code since there are two versions. The -10x series is 120mT and the -00x series is 50mT, you’ll get a trade-off of precision and range.
See more from the manufacturer video below: