bcm2835 lib version 1.69 and node-red rpi-dht22 error

[fa-schmidt]

Hello all,

I am just a user, no developer. So I apologize in advance for my incompetence :)
I followed this tutorial :

DHT22 + Node-RED on Raspberry Pi = Humidity and Temperature Logging (ruk.ca)

to get my Raspberry Pi 3B version 1.2 and node-red up and running with a DHT22
sensor.

Instead of the mentioned version 1.58 i used the newest 1.69 lib of bcm2835.

Everything compiled and installed without (visible) error.

I can run node-red with some test nodes but whenever using the dht22 node
the message payload is:

object

_msgid: "a85c66ec.cca5e8"

payload: "0.00"

topic: "rpi-dht22"

humidity: "0.00"

isValid: false

errors: 4

location: "Test"

sensorid: "dht22"

Testing my sensor on that exact system with a small Python program that uses the
Adafruit lib is succesfull.

So how can I get helpful information on what goes wrong?
I would appreciate any info.

T.i.a. Frank 

[Mike McCauley]

Hello,

Did you try it with http://www.airspayce.com/mikem/bcm2835/bcm2835-1.58tar.gz
as suggested in the instructions for your project?

On Tuesday, 6 April 2021 23:27:36 AEST fa-schmidt wrote:
> Hello all,
> I am just a user, no developer. So I apologize in advance for my
> incompetence :)
> I followed this tutorial :
>
> DHT22 + Node-RED on Raspberry Pi = Humidity and Temperature Logging (ruk.ca)

> <https://ruk.ca/dht22-node-red-raspberry-pi-humidity-and-temperature-loggin
> g>

>
> to get my Raspberry Pi 3B version 1.2 and node-red up and running with a
> DHT22
> sensor.
> Instead of the mentioned version 1.58 i used the newest 1.69 lib of bcm2835.
> Everything compiled and installed without (visible) error.
> I can run node-red with some test nodes but whenever using the dht22 node
> the message payload is:
>
> object
> _msgid: "a85c66ec.cca5e8"
> payload: "0.00"
> topic: "rpi-dht22"
> humidity: "0.00"
> isValid: false
> errors: 4
> location: "Test"
> sensorid: "dht22"
>
> Testing my sensor on that exact system with a small Python program that
> uses the
> Adafruit lib is succesfull.
>
> So how can I get helpful information on what goes wrong?
> I would appreciate any info.
> T.i.a. Frank

--
Mike McCauley VK4AMM mi...@airspayce.com
Airspayce Pty Ltd 9 Bulbul Place Currumbin Waters QLD 4223 Australia
http://www.airspayce.com 5R3MRFM2+X6
Phone +61 7 5598-7474

[fa-schmidt]

Thanks for the answer.
Yes, I followed the instructions very carefully and did not encounter any error during this.

In the end I "solved" the problem by buying a new DHT sensor.

The sensor I used was unlabeled, of unknown origin.
It worked fine with Python but not with NodeRed and the BCM lib.

The new sensor is a labeled one. It is an DHT22 / AM 2302 model . Plus I got a DHT11 
as well.

Both new sensors work !

Problem now is: Both work inreliable.
After hours, but always within a day, the values are tagged "isValid = false".

The values freeze to the last known good one.

To overcome this I have to cut off power. Reboot does not help. 

So I think there is something else going on which has nothing to do with the lib.

In order to finish my project, which is about monitoring room conditions over a long
time continously, I now bought a BME280 sensor and use the NodeRed bib someone has created.

Lets see where this goes. Maybe I do some more test. Monitoring CPU core voltage or so
or digging deeper into logs but I have to finish my project at first.