Issue with MH-Z19 sensor !!

[vincen]

Hi,

Trying to use the MH-Z19 sensor on my ESP unit but encounters a problem. I have updated my ESP to ESP 2.0 dev 11 so to get MH-Z19 implemented in it.
I declare it this way:

and list of all devices in my system (first one is disconnected right now so normal it has no value !):

If I wire it same way as wiki I get these errors in log of ESP:

19535 : MHZ19: Read error : CRC = 81 / 33 bytes read => 255/255/255/255/255/255/40/140/33/
19538 : MHZ19: Shifted 2 bytes to attempt to fix buffer alignment

and if I reverse TX/RX lines from MHZ to ESP, I got that:

383777 : MHZ19: Error, timeout while trying to read
383778 : MHZ19: Unknown response: 0 0 0 0 0 0 0 0 0

so it looks like wiring of Wiki is correct (which makes sense) but what are these CRC errors ??

Vincèn

[LisaM]

Pics of the wiring?

[LouiS22]

I have the exact same problem Briefly I was able to make it work but all of a sudden it's just not working anymore. I'm on dev11 as well.

[LisaM]

Code: Select all

718891021 : MHZ19: PPM value: 612 Temp/S/U values: 20/64/10360.00
718891022 : EVENT: MH-Z19#PPM=612.00
718891103 : EVENT: MH-Z19#Temperature=20.00
718891183 : EVENT: MH-Z19#U=10360.00

Working reliable for some time now...

[vincen]

Pics of the wiring?

Well I followed indication of Wiki:
3.3V from ESP -> Vin MH-Z19
GND -> GND
2 GPIO declared to RX and TX or reverse

Crossed and uncrossed TX/RX but not really much more luck out of error log different but not working !

[grovkillen]

And you are sure the sensor is not broken?

[vincen]

And you are sure the sensor is not broken?

it's brand new but I have only one so difficult to know if it's working or broken

[grovkillen]

As it seems that you have wired it correctly and also the settings seems fine I'd like to try another sensor instead of starting to turn more stones.

[LisaM]

Pics of the wiring?

Well I followed indication of Wiki:
3.3V from ESP -> Vin MH-Z19
GND -> GND
2 GPIO declared to RX and TX or reverse

Crossed and uncrossed TX/RX but not really much more luck out of error log different but not working !

How long are the wires?
CRC errors might point to a wiring problem.
Where is the 3.3v coming from?

[vincen]

How long are the wires?

15cm approximatively

CRC errors might point to a wiring problem.
Where is the 3.3v coming from?

3.3V is coming from the ESP board and I used it previously to power some pressure and temperature sensor without problems !

[LisaM]

3.3V is coming from the ESP board and I used it previously to power some pressure and temperature sensor without problems !

MH-Z19 sensor technical parameters:
Working voltage 4.5 V ~ 5.5V DC
Average current < 85 mA
Interface level 3.3 V

I have mine connected to 5V, yours is starving...

[grovkillen]

The wiki started (wrongfully) 3.3V, I have now fixed it (5V).

The logics are 3.3V based though, no level converter is needed.

Thanks Lisa!

[vincen]

The logics are 3.3V based though, no level converter is needed.

Just to be sure it means I still need really 5V to power correctly the sensor right ?

[grovkillen]

Yes, communication is 3.3V based.