Thingy91 thermometer gets heat up after couple of minutes

[Karol Grodzicki (Speeron)]

We'd like to use Thingy91 to measure temperature, but it looks like the thermometer (BME680 onboard) gets heat up, when Thingy91 is running for some time.

I placed the device next to analog thermometer showing 19°C. The device wasn't powered on for a day, so should have the same temperature. When I powered on Thingy91 (on battery) with Asset Tracker v2 app, it started to send data to cloud and at start it was indeed 19°C, but after two minutes it got to 23.5°C (see image below). I took out the board from the plastic box, so it's not the proximity of the battery - it probably is heated by circuits around

How could we work around this issue? Is it possible to somehow calibrate the sensor or should we apply the correction ourselves?

[Kazi Afroza Sultana]

Hello Karol,

The increase of the temperature is basically coming from two points, GPS and Charging:

1. Default settings in Asset Tracker v2 will turn ON the GPS in specific intervals and that will increase the temperature on the PCB close to the sensor. To disable the GNSS just disable the module in the configuration file "prj.conf" [CONFIG_GNSS_MODULE=n]

2. Charging the device can also increase the temperature. To fix that you would only power the Thingy:91 with the battery (USB disconnected) or disconnect the battery and power the Thingy:91 with the USB only"

Our team is currently working on a pull request to enable some other libraries to get more accurate temperature and inclusion of the Air quality measurements. You will be informed when the test and the verification of results are done. Our team will contact you. Till then you do not need to apply any correction by yourselves. 

Thanking you.

Best Regards,

Kazi Afroza Sultana

[Karol Grodzicki (Speeron)]

Thank you, I've added CONFIG_GPS_MODULE (not GNSS, this didn't work) and also added low-power overlay (disables LED, logging etc.) and we got 21.9°C, which is definitely better

I've tested everything on battery-only, probably we'll remove batteries on production then. I'm looking forward to new features

[Martin Lesund]

Great to hear that it worked out.

The reason, why CONFIG_GNSS_MODULE did not work for you, is because that name change came in nRF Connect SDK v1.9.0 that was released yesterday. 
(nRF Connect v1.8.0 uses CONFIG_GPS_MODULE)

There is now a Pull request out that shows how to include the BSEC library so you can include the Air quality readings by enabling the library. Instructions on how to set this up are included in the commit as well.
(The BSEC library needs to be downloaded from this page) The Air quality parameter will show up on nRF Cloud dashboard when enabled.

If you have any questions don't hesitate to ask