Accessing DHT 11 Sensor in Node Red using Raspberry Pi

[Kyaw Zin Latt]

Hi,

I am a student. I would like to know how to access DHT11 sensor data using rpi-gpio nodes in Node Red. I also wanna know the FLOW of nodes in Node Red if possible.

Thanks 

[Mark Setrem]

The DHT11 requires a library to convert the reading to a temperature.

One way of getting the temperature reading into Node-red would be to follow the instructions here: https://www.endian.se/content/?p=127

and then use the "exec" node to execute the Unix command to get the result into Node-Red

alternatively you might be able to read the file with the File Read Node.

[Kyaw Zin Latt]

Thanks for your advice. As I am very new to Node Red, could you please show me step by step?

[Scott C. Lemon]

This is actually a nice little program ... it could be easily modified to output JSON by adding a new "format" type to it ... and then it would come into Node-RED quite easily with EXEC.

Note to self: give it a try this weekend ...  :-)

[Mark Setrem]

Before starting on Node-Red, follow the instructions in the original post, when you have that part working, then you can think about getting the data into Node-Red.

But I'd try something like an "Inject">"Exec">"Debug" flow...

[Kyaw Zin Latt]

Thanks a lot. It is working now. Btw, is there any other way to get sensor data in Node Red using rpi-gpio nodes?

[Mark Setrem]

Glad you got it working.  It depends on the sensor you want to connect.  

For some such as a PIR proximity sensor (on or off) it's easy to link it and read it directly.

For others such as the DHT11, which require a more complex technique, I personally think that life is too short!

[Dave C-J]

Hi

the GPIO nodes are really only for simple digital IO - so reading switches, PIR, that sort of thing. Anything more complex that needs a communications channel (like reading the DHT11 etc) is better off handled by some native code as per the pointers already given. In theory someone could write a native module and then wrap it in a node.js wrapper to help make a node - but that would be a considerable effort for a fairly specific result. Much better (imho) to use the general approach already outlined (ie write to a file, or socket) and then read that into Node-RED.

[Kyaw Zin Latt]

On Tuesday, August 26, 2014 5:12:04 AM UTC+8, Dave C-J wrote:

Hi

the GPIO nodes are really only for simple digital IO - so reading switches, PIR, that sort of thing. Anything more complex that needs a communications channel (like reading the DHT11 etc) is better off handled by some native code as per the pointers already given. In theory someone could write a native module and then wrap it in a node.js wrapper to help make a node - but that would be a considerable effort for a fairly specific result. Much better (imho) to use the general approach already outlined (ie write to a file, or socket) and then read that into Node-RED.

Thanks a lot for your explanation

 

[Kyaw Zin Latt]

Thanks a lot for your discussion.