Sensors - components used and cost

[vucalur]

Hi folks, I came across an article stating, that the cost of your sensor would be very low, i.e. 35 PLN and below. Is that a correct quote?

For an unit equipped with wifi connectivity, battery, that would be an insanely low price. PMS5003 sensor alone costs twice as much. Could you share some details which components do you use along with where to get them from?

Best, vuc.

[Nuanda]

Hello. Yes, the "quote" (or, precisely speaking, the prototype cost estimation) was around that figure, back in December 2016. It was based on an extremely cheap Sharp GP2Y1010AU0F (then: $5.39), and the other elements (WiFi esp8266, ATtiny13A, DHT11) were around $3.5 taken together. This, however, did not take into account the casing and the batteries - just the bare electronics put together and made to work, in a matter a couple of hours (it was a hackathon). We were still, however, aiming at the <100 PLN mark.

I am not sure if you can still get them - there may be some updated (and, perhaps, more costly) versions available now. But please keep in mind you need to put all this together by yourself.

As to our plans, we have run some extensive tests of the cheap Sharp sensor quality over the 2016 and, unfortunately, the results were not really convincing, even after a complex calibration, when compared to the official PM readings. So a part of our team decided to go ahead with another, laser-based, costlier (but also - more reliable) solution and we ceased to pursue the "lowest price possible" target.

[vucalur]

Thanks. If the info about the components you use is not classified, I think it would be good to share it either here in some wiki/*.md docs or on a blog/website if you run one. Along with the findings regarding Sharp sensor dependability.

After all, if I got it correctly, you aim at individuals constructing sensors and contributing readings from numerous locations to your map. Calibration might be an issue, but I think it's still a better idea than selling sensors for 1000pln, which certainly puts off most of individuals. That's what some other company does, I'm sure we both know who we're talking about.

But please keep in mind you need to put all this together by yourself.

Indeed. Time required for assembling and programming along with learning how to do that is the biggest cost, hence using a reliable sensor is more important than saving some 50pln. It's second source stating that Sharp sensor, being a led-based, isn't that much reliable.

[Nuanda]

Not classified, as I've just posted it on this public GitHub project :). The old Smogathon 2015 website (http://2015.smogathon.pl/ - down :( ) used to have a link to a google drive folder with all our presentations, including the component lists. Smogathon's Maciek Ryś is probably able to point you to the right place (I can't find it now). Anyway, I listed pretty much all components in my previous post.

Regarding reliability testing, we were doing that mainly with Michał Kiełtyka (now in airly.eu), the guy behind our smogathon2015 sensor (I was doing the web and the DB programming, I'm not an electronics person), using our smogmapper platform. In the meantime other people from airly.eu were testing laser sensors, using the same platform, and we were comparing our readings to WIOŚ readings - trying to calibrate the equipment (though I think the laser one hardly required any calibration).

As I wrote, in autumn 2016 they decided to drop the cheaper solution and went ahead with their business using the more expensive one. And they moved to their own data acquisition system, so the bulk data is no longer available to me.

If you are interested in all 2016 readings from the Sharp-based sensor (btw please remember, the final quality of particulate matter readings depend not only on the sensor, but also on the sensor placement, the calibration transform re. humidity and temperature, the casing...), you will need to talk to Michał Kiełtyka. I could be able to send you the raw data itself, but without his input on how that data was really measured, I think it is useless.