[Barrow4491]

Well, don't know if that will be a good idea, the readings of the temp / hum sensor will be largely influenced by the heat produced by the Nano and the voltage regulator.
Actually the temperature reading isn't used by the software for any calculation, but the readings of the air moisture are used on the calculations of the PM2.5
Current investigations also seem to reveal that air moisture affects CO2 readings, so in future software releases, the RH may also be used by the CO2 calculations.

Werk,

The fact that I had no temperature sensor plugged in i thought may be causing the weird high temp and RH readings, so i disabled the line"use_RH comp" in the config and recompiled and that fixed it, but still no data being sent to the Rx.

I then decided to use the new board, which had since arrived, and powered the HTU21D from the 3.3 volt pin on the nano as suggested by Uncle_bob. Powered it up and everything seemed to be as expected and I am receiving data on the Rx about every 35 seconds or so, except that yesterday the CO2 readings weren't coming through. Ran the serial monitor and it reported that the readings were incorrect, so I have since disabled it and ordered a new one.
The cause of the regulator failure is a mystery as the same temperature sensor on 3 volts is working fine with the new board and it is now transmitting reliably with the same components.
Regards
Jim

Attached are some photos of the assembly and the Stevenson screen which will mount outside. The screwed cap on the top is to access the usb for program updates

[hornychz]

Attached are some photos of the assembly and the Stevenson screen which will mount outside. The screwed cap on the top is to access the usb for program updates

Very nice box! Congratulations.

[JT118]

I have not seen a radiation screen like this before, where did you get it? Is it home made? Very neat.
Yellow will get hotter than white so your ambient temperature will be a bit higher than it really is. It should not matter for the AQI.

[Barrow4491]

I have not seen a radiation screen like this before, where did you get it? Is it home made? Very neat.
Yellow will get hotter than white so your ambient temperature will be a bit higher than it really is. It should not matter for the AQI.

Thanks,I 3D printed it myself and will paint it white before installation although it will not be in direct sunlight but on our first floor balcony
Regards
Jim

[werk_ag]

... It should not matter for the AQI.

I think it matters. Temperature affects how internally the sensor calculates RH.
And RH is used to compensate PM readings.

PM readings should be compensated in function of RH, Sharp even sugests this function:

beta = Humidity factor
if (rh > 50.0) beta = 1- 0.01467 * (rh - 50.0);


WeatherDuino AQM usis this:
if (Humidity > 50.0) beta = 1.0 - (0.016 * (Humidity - 50.0));
PM2.5 = PM2.5_raw * beta


However, as the enclosure designed by Barrow4491 allows a great air flow, the heat produced by the Nano and regulator shouldn't affect greatly the readings.

By the way:
Barrow4491, you did a nice work.

[Barrow4491]

... It should not matter for the AQI.

I think it matters. Temperature affects how internally the sensor calculates RH.
And RH is used to compensate PM readings.

PM readings should be compensated in function of RH, Sharp even sugests this function:

beta = Humidity factor
if (rh > 50.0) beta = 1- 0.01467 * (rh - 50.0);


WeatherDuino AQM usis this:
if (Humidity > 50.0) beta = 1.0 - (0.016 * (Humidity - 50.0));
PM2.5 = PM2.5_raw * beta


However, as the enclosure designed by Barrow4491 allows a great air flow, the heat produced by the Nano and regulator shouldn't affect greatly the readings.

By the way:
Barrow4491, you did a nice work.

Thanks
When I was designing the screen I wanted the centrepanel vertical with the sensors on one side so that both got a good clear airflow and the pcb on the other side with the HTU21D at the bottom to avoid any heat effect from the regulator or Nano.
Regards
Jim

[JT118]

I was not referring to the heat generated by the Nano, more the heat absorbed from the sun by a yellow screen, but if it is to be painted white it does not apply. Yes I know the calculation for the AQ relates to temperature but that is to compensate for the air temperature entering the sensor. Therefore hot or cold the temperature will be compensated for within the formula.

[Barrow4491]

The AQ index appears as a co loured scale with a pointer: what is the numerical range?
Jim

[werk_ag]

WeatherDuino AQI index scale follows U.S. Environmental Protection Agency standard.

https://www3.epa.gov/airnow/aqi_brochure_02_14.pdf

Range is from 0 to 500

[Barrow4491]

Werk,
The AQ monitor has been going reliably but this morning the attached images show what happened; I rebooted the unit and it came good. Any ideas??