A perfSONAR User's Group

Temp/Humidity with Raspberry Pi

 

Found myself answering this question at the recent Internet2 Tech Exchange in Indianapolis —

Can you add temperature and/or humidity sensors to these small devices easily?

I have done this with Raspberry Pi more than once. I took old ribbon cables from floppy drives, shortened one connector with a hacksaw, and then cut the other one off, giving individual wires to play with.

Once you have a way to break out the pins —

(you may rather do something like: http://www.adafruit.com/products/914 )

the DS18B20 :
http://www.adafruit.com/search?q=ds18B20&b=1

allows you to sense N > 1 temperatures per 3-wire connection on a bus,

and the DHT22:
http://www.adafruit.com/search?q=DHT22&b=1

gets you temp/humidity one-per-3wire-connection.

The attached graphs are from sensors at my house — the 5-line graph is a chain of DS18B20’s and the 3 line graph is temp and hum from a DHT11 (the cheaper version of the DHT22 I mention above), with calculated dewpoint. I would reach for the DHT22 if I did more sensors, given the aliasing noise you see on the graph.

Pins on the Raspberry Pi differ from model to model and can be really
confusing.

http://wiringpi.com/pins/

Once you get the connections right, regular old Raspian, the default
Linux for Raspberry Pi, has a kernel module for Dallas 1-wire to read
the DS18B20’s and AdaFruit.com has source code for the DHTnn devices.

BeagleBone white/black also have the capacity to read pins, probably
duplicate each of the above, but I have RPi’s at home, and all my BB
belong to the UH, so I’ve done more interfacing with the personal stuff…

-Alan Whinery

dht11day

week-ng

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