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I have a Rpi with 3 DHT22 sensors attached. They share a common VCC/GND and the data lines are plugged into 3 separate GPIOs.

I had the system breadboarded for a while and never had issues, but recently I've noticed that 2 of the 3 DHT22s stop working after a couple of hours and then the 3rd DHT22 stops responding a while after that. A quick shutdown, unplug/replug gets the whole thing working and recording temp/hum again (for a few hours).

The whole setup worked for about a year and then the DHTs started acting a little flakey, so I figured that I'd change the sensor (always a chance that cheap sensors go bad). After swapping out the sensors I started getting the current behavior of DHT22s slowly stopping responding after some time.
I've removed all other sensors/relays/etc from the system so it doesn't seem to be related to inter-component comms.

I'm not sure what else could be causing the problems here.

Does anyone have ideas on what to try?

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As fas as I am aware this is a fairly well known problem with the DHT22 (models such as the DHT11 do not seem to be affected).

After a random amount of time which can vary between seconds and months they stop responding. The only solution I am aware of is a power cycle.

A solution I have used is to power the DHT22 from a Pi GPIO. The GPIO can supply the limited current needed and is within the device specs of 3 to 5 volts. If I detect a number of consecutive timeouts I switch the GPIO off then on again a few seconds later.

An example of such code is my pigpio Python module DHT22.

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  • I'd heard that this was a common'ish issue, I hadn't seen any references to powering the sensors via switchable GPIOs. Makes sense that these sensors are lightweight enough to be able to run off that power. I had thought of running this power connection through a relay that I could switch, but using another GPIO is much simpler, and already wired up. – ChrisC Jan 29 '20 at 17:04
  • I looked into the gpio-pin power thing, but couldn't see that I would be able to get anything greater than 3.3v and my temp sensors are wired with more than 1m of cable (so really need the 5v). Ended up utilizing a relay to depower. Thanks for the helpful advice! – ChrisC Jan 31 '20 at 13:47

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