[werk_ag]

Hi Jim,

Not to be deterred i replaced the regulator again and reloaded with V6 software and turned it on with no sensors plugged in and it came to life again with the 5 volt rail reading 4.9 volts
I plugged the sensors in one at a time with no issues until it came to the HTU 21D but it refused to reboot. Unplugging the module solved the problem and it rebooted OK. It has now been running for 20 hours with no regulator issues.

Now you know what have damaged the voltage regulator. The original board wasn't defective.
By the way, seems that the new AQM board wasn't arrived yet, so you should get it very soon.

1   I then noticed that the HTU21D sensor has a maximum vcc of 3.9 volts but the circuit provides 5 volts. I have searched the internet looking for a 5 volt version to no avail, and as per the screen shot the temp and Rh values are 998.0 because of the lack of a sensor.

Here is a link to the 5V version, it's very common

https://www.ebay.com/itm/HTU21D-Temperat...SwW9ZZccVf

2   The values for PM 2.5 and PM 10 are negative and the AQ Index value is 0

Check the connections of the sensor with the board. You can activate the debug functions on the software to check if the sensor is being read correctly.

3   It took overnight ??? for any values to appear in my Rx and only the CO2 is shown.

If there are problems reading any of the sensors, you may not receive any data at all. Otherwise, after an initial period of 3 minutes, data is sent to RX, more or less at each 35 seconds.