PMS7003 stays at 0

1

Hi,
I can’t remember if I have already asked here.
The Respire Community in Paris as a full batch of customized sensors which are distributed to its supporters in France.
It is basically SC sensors with a screen and a PMS7003 instead of the SDS011.
Some of these sensors where built quite a long time ago (more than 1 year) and are still being distributed. A long story…
Already for 1 year, I have seen a sensor staying àt 0 for quite a longtime (actually forever, we had to replace it). For the past few weeks it happens very often. Some come back to life after a while but some others are really blocked at 0.
Today a test with a cigarette (I was on phone checking on our online dashboard) produce some high values but it came back to 0 after a while.
According to my experience, it seems that all these broken sensors where at first connected to very bad PSU sometimes for a few days (and the person could not succeed to type a password the right way…). Do you think that the under amperage can damagne the PMS7003?
Has someone such experience?

Screen Shot 2023-08-11 at 22.52.54
Screen Shot 2023-08-11 at 22.52.541422×328 29.3 KB

And again this intermittent stuff… It happens only in France!

2

The PMS sensors need some resistors when using the UART interface. I couldn’t find the datasheet, but the PMS1003 is similar and needs high potential on the reset pin (low is reset) and on the set pin (low is sleep mode). So there should be 10k resistors between 3.3V and the mentioned pins at the PMS sensor.

3

You mean this?
Screen Shot 2023-08-12 at 07.55.42

The small board is on the PMS and for most of the sensors no issue. Maybe a connection issue because the sensor were shaken by Respire…

It is a first idea.

4

The mentioned connections are really important. Set and reset need to be on high level, without high level the sensor will either be in sleep mode or reset the whole time…

5

We have over 200 units with PMS7003 installed. A couple were found dead on arrival, but most work for years in power-switched mode. Sometimes they fail and come down to zero readings - but usually it is a board failure due to poor housing or corrosion. One sensor was found stuck on high readings - it shows ~10x amplified values, that’s really odd.
Now just notes:
poor PSU can cause malfunction of the whole system but cannot damage the sensor;
PMS7003 work perfectly with Set and Reset pins left floating, they have internal pull-up resistors;
you can always test the PMS7003 with any UART adapter as they are set by default to send the readings each second