Explorer phat with DHT22: read values


#1

Hi

I bought the explorer phat to connect analog sensors to my pizero. This works perfect!
I also want to connect a (digital) temperature and humidity sensor (DHT22, a AM2302 th be exact). I already connect it directly to the pi using this schematics. With the software from adafruit, I can read out the sensors values without a problem.

However, with the explorerhat, I cannot set it up directly on the pins. So I connected the wires to 5v, ground and input1. The sensor can handle the 5v according to the datasheet.
Now here’s my problem: With the functions from explorerhat I just get a "high state"on input one (explorerhat.input.one.read()=1). But I want the temperature and humditiy values. In the documentation for the explorer hat (the phat is never mentioned, I assume it works for both?), I read that input 1 is connected to GPIO 23. So It thought I can just read it out with the adafruit software, but this: _sudo python AdafruitDHT.py 2302 23 gets me always a “Failed to get reading. Try again!”.

Can anyone help me get the readings from the digital sensor DHT22 with the explorer phat?

Thank you in adavance and please excuse my writing as I’m not a native speaker.


#2

To isolate the problem: Is it correct that “Input 1” from explorer phat is connected to GPIO23?


#3

yes: http://pinout.xyz/pinout/explorer_phat

I need to pull my finger out and see how a DTH22 read out would work with the Explorer (btw, yes the pHAT would work identically to the HAT in this respect).


#4

Ok. Thanks for the information.
From your answer I guess it is not the same if I connect the digital out to the explorerhats “input 1” or rather direct on the GPIO23?
If this is not the same, I think a solution is beyond my abilities. So I’d be grateful if you know some documentation or examples for that kind of problem. Maybe I can figure it out with some help…

Is this maybe of any use:? https://github.com/adafruit/Adafruit_Python_DHT/blob/master/source/Raspberry_Pi_2/pi_2_dht_read.c


#5

I don’t think the Explorer inputs are particularly adapted for one-wire communication.

Ideally you would use a spare pin on the Pi GPIO. The pHAT is quite ideal for that since you can solder a passthrough header.

If it’s a permanent application then perhaps the most practical would be to solder the AM2302 on top of the pHAT (making sure to use a pin not used by the Explorer)?


#6

This seems to be the simplest solution. Thank you.