Hi all!
We are pleased to announce a new firmware release for the SCK2.X series (2.1, 2.2 and 2.3). This release has some new features and an important change on the SEN5X: Release 0.9.11 · fablabbcn/smartcitizen-kit-2x · GitHub
Firstly, we have introduced a new correction method for T/RH readings. You can read more and give us feedback here: New firmware feature - Temperature and relative humidity corrections or via issues on the firmware repository.
In addition, a small couple of fixes were introduced for the OLED display to fix some minor details.
However, the most important issue that we solved is the SEN54 and SEN55 sensors firmware. This was firstly fixed by a PR by @pylonsoft (big thank you for that!): Fix continuous mode readings by pylonsoft · Pull Request #92 · fablabbcn/smartcitizen-kit-2x · GitHub
This PR addressed a problem for the SEN54 and SEN55 in what we called continuous mode. These sensors have a VOC (SEN54) and a VOC + NOx Index (SEN55) sensor in parallel to the PM sensor that the SEN50 has. They also include T and RH sensors.
In continuous mode, the SEN54/5 are operated always on, but a bug in the firmware made the readings be updated erratically, making these sort of graphs (see the squaredness of the signal).
These erratic readings were returned every time the VOC or NOx index were enabled, making PM readings also wrong. In a SEN54 or a SEN55 we did not have these metrics enabled by default, and this issue was not present in SEN50 (as there is no VOC or NOx index). If you have enabled the VOC or NOx indexes by hand, the data was not right.
Thanks to @pylonsoft’s PR, we have solved this, making the readings work as they should (see the graph above and how the signals look like).
However, there is an additional improvement that was introduced on this firmware release. The so-called continuous mode operated the sensor in what Sensirion calls MEASUREMENT_MODE, which basically means, always on. This meant that we had the PM sensor fan always on, with a significant power consumption and heating up the SCK.
In a separate PR, we fixed this by allowing the transition between MEASUREMENT_MODE and the RHTGAS_ONLY_MODE. This mode turns off the fan, doesn’t return PM, but allows the NOx or VOC sensor to be on so that the internal algorithm works well in the sensor itself.
This means several improvements:
- Lower power consumption (see battery improving from some 12-14h to a couple of days):
- Lower heat build-up on the device (by a couple of degrees):
- No impact on PM readings, and or other metrics.
With this, we have now changed the defaults to enable VOC or NOx index if you have a SEN54/5. Before, they needed to be turned on by using the shell.
Finally, a small advice. If you are using the VOC index, take into account that the SEN54/5 has an internal algorithm were the sensor “learns” and stabilizes its readings. We keep track of the algorithm state in the SCK, and if there is a short power interruption, we feed it back to the sensor. However, we have seen that the sanity reset affects these readings. If you are interested on the VOC index, you may want to switch the sanity reset off in the Shell.
config -sanity off
Hope this works for all you! Let us know via comments or issues!