MH-Z19 only reports temperature when connected to ESP-01

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ix-trader
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MH-Z19 only reports temperature when connected to ESP-01

#1 Post by ix-trader » 17 Jan 2022, 00:24

Hello ESPler.,

Hoping sombody had the same problem with an solution.

I try to us an MH-Z19C Sensor with an ESP-01 Board with fimrware ESP_Easy_mega_20211224_normal_ESP8266_1M.bin. (I also tried older fimware with the same result)
The sensore only reports the correct temperature an always reports PPM value of 5000 sometimes (500). The Temperature is changing as you can see in the log:

Code: Select all

501427: MHZ19: PPM value: 5000 Temp/S/U values: 20/0/0.00
1501855: WD : Uptime 25 ConnectFailures 0 FreeMem 17424 WiFiStatus 3 ESPeasy internal wifi status: Conn. IP Init
1503425: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1505427: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1507425: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1509425: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1511425: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1513426: MHZ19: PPM value: 5000 Temp/S/U values: 21/0/0.00
1515425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1517425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1519425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1521426: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1523425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1525425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1527425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1529425: MHZ19: PPM value: 5000 Temp/S/U values: 22/0/0.00
1531425: MHZ19: PPM value: 5000 Temp/S/U values: 23/0/0.00
1531855: WD : Uptime 26 ConnectFailures 0 FreeMem 17424 WiFiStatus 3 ESPeasy internal wifi status: Conn. IP Init
1533425: MHZ19: PPM value: 5000 Temp/S/U values: 23/0/0.00
An ESP12E DevKit connected to the same MH-Z19C hardware but with firmware ESP_Easy_mega_20210503_normal_ESP8266_4M1M.bin the PPM Value is reported correctly.

Is it possible that the memory of the ESP-01 is not sufficient?
Should I use a different firmware?

Kind regards
Martin

TD-er
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Re: MH-Z19 only reports temperature when connected to ESP-01

#2 Post by TD-er » 17 Jan 2022, 10:14

ESP-01 does have a very limited amount of pins available, so I wonder what pins do you use?
Is it the same pins as for Serial-0?
If so, make sure that you have "Use Serial" unchecked at the tools->Advanced page.

ix-trader
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Posts: 2
Joined: 17 Jan 2022, 00:01

Re: MH-Z19 only reports temperature when connected to ESP-01

#3 Post by ix-trader » 22 Jan 2022, 19:33

I disabled the the settings as proposed. But with no effect.

After some Inverstigation I found the Solution. The MH-Z19 needs 5V Input Voltage to work properly.
I was confused by the Technical data stated "Working voltage 3.6 ~ 5.5 V DC". But this dose not mean that it can work with this voltage range but has the serial interface at 3.3 Volt and the Input Votage of at 5V.

Thanks for your support!

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