Dust Sensor SDS011 Reading too low

[whatsupskip]

I had set up the Dust Sensor SDS011 about six months ago and it was working correctly. I hadn't used it for a few months and now when I use it the readings are too low. That's is, most of the time PM2.5 is reading 0 to 1 and PM10 2 to 10. I doubt this is a code error as I haven't updated the ESP8266 code since it was last working. I have tried in sleep modes and continuous. Has anyone else had a similar problem?

Otherwise I assume it has died

I am wondering if "sleep time" or the way I configured it, has only been putting the fan to sleep and not the laser diode as that is what fails in these sensors.

[Ath]

Due to the nature of the sensor it seems appropriate to ask if you cleaned it, before putting it back to use?
These kind of sensors seem quite sensitive, and excessive dust inside the sensor sounds like a plausible cause of malfunctioning.

[chemmex]

Before assuming it dead you can test the sensitivity with any kind of smoke. The laser can degrade over about a year if constantly on, but I doubt that is your case.

[TD-er]

As far as I understood the inner working of this sensor, it counts the number of interruptions of a laser beam.
But what if the 'eye' of the sensor (or the laser) is obstructed with dirt, then it may be impossible to detect any interruption.

Not sure if smoke will have an effect, but starting a BBQ for sure is something that will be measured by the sensor.

[whatsupskip]

Due to the nature of the sensor it seems appropriate to ask if you cleaned it, before putting it back to use?
These kind of sensors seem quite sensitive, and excessive dust inside the sensor sounds like a plausible cause of malfunctioning.

It hasn't been exposed to high levels of dust. I can't see any dust around the entrance or exit, but I will get out some magnifying lens to look more carefully. I was wondering if a spider or some other creature has set up home inside it. I have had this happen with smoke detectors before.

[whatsupskip]

Before assuming it dead you can test the sensitivity with any kind of smoke.

I tried this and the peak smoke levels look reasonable with PM10 over 1500 and PM2.5 over 700. The levels then dropped down to what I would have thought were too low, but then came up again to about what I would have thought would be correct (both around 40). This still seem too low though. For the moment it appears to have lost sensitivity with low levels of particulate.

Thanks for all the suggestions.

[Remco v/d Oosten]

Dear Ath and all,
my SDS011 got accidentaly into a heavy dust cloud while working. High peaks, now constant low value 5 for PM2.5, too low values for PM10 by a factor of 5 or so as compared to neighbouring stations that compared very well before.
What would be an appropriate cleaning procedure for the sensor? I don't want to literally blow it up by flushing with a certain overpressure...

Any help and hint is highly appreciated!

Remco v/d Oo.

Due to the nature of the sensor it seems appropriate to ask if you cleaned it, before putting it back to use?
These kind of sensors seem quite sensitive, and excessive dust inside the sensor sounds like a plausible cause of malfunctioning.

[TD-er]

I think blocking the fan and pressured air may be my first guess to clean it. (reason to block the fan is to prevent high voltage damaging the sensor electronics if the fan starts acting as a dynamo)
It all depends on whether the dust was dry or moist.
If it became sticky, then you must probably open it to clear the dust from the laser and/or optical eye.

Very likely you should already order a new one...

[Remco v/d Oosten]

Hello TD-er,

thanks for your swift advice, looks like I need to get a bit deeper into the technical details - and order a back-up or follow-up
Best, Remco

[whatsupskip]

Hello TD-er,

thanks for your swift advice, looks like I need to get a bit deeper into the technical details - and order a back-up or follow-up
Best, Remco

Please let us know how your cleaning and opening went. I looked to try and open my, but couldn't see an obvious non-destructive path.