Brent nerd sniped me this week with his talk of a non-contact thermal sensor for Leaf VPD measurement on WipperSnapper, as I've been wanting VPD measurements of my Banana plant for a very long time.

Limor then came in with some suitable new sensor alternatives (the TMP007 being obsolete), and my mind wandered through the digikey site briefly, stumbling upon the D6T thermal sensor series from Omron.

Conveniently it uses a very similar cable to my favourite sensors, the JST-GH locking cable, but a 4pin variant. No Problem! Cut the 6pin version right through pin 5 (then removing the 5th wire and contact), and a final extra trim of the locking tab, and hey presto an instant fit!

Easy pinout, as it's I2C, but wants 5volt power/logic. The handy StemmaQT 3v to 5v logic level converter (PID 5649) quickly gets you to stemma and voltage compatibility. Then for software Omron have a library on Github.

Sadly it looks unmaintained, or at least incompatible with ESP32. So a quick fix or two (merge some old community PRs -❤️open-source), rebase it, swap the Wire (I2C) to be a passed argument, and now it's hopefully suitable for all!

This is the connector / pinout details:

Finally, you'll want to know that the library has an ambient temperature, i.e. the device, which runs a bit hotter than ambient, and then also the object temperature (or multiple depending on sensor model).

PTAT measurement (Proportional To Absolute Temperature) is the ambient / unit temperature.

You can grab the latest code from here (tested versions 1.0.0-1.0.4), or it's now findable in the Arduino library registry, i.e. just search D6T in your arduino library manager.

https://github.com/tyeth/omron-devhub_d6t-arduino

And the datasheet is here:

https://omronfs.omron.com/en_US/ecb/products/pdf/en_D6T_users_manual.pdf

Initial feedback:

They appear run a bit hot, and detect hotter than expected when facing up towards underside of leaf in incredible sunshine. Also tested against icecream which read -4c on the container 1-2mins out the freezer (-15c to -18c).

Nothing conclusive and I should do some proper testing against ice / boiling water with a DS18b20/thermocouple and thermal camera comparison.

It might be interesting to test the multiple pixel models of the same family, but until v2 of WipperSnapper we don't have a good way to return that data (>2 of same sensor subcomponent type).