Low-Budget Room Monitoring with JeeNode

Having several JeeNodes around the house, and some of them as RoomNodes with the quite pricey (~20€) SHT11 Sensor, I was looking for quite some time for a cheaper replacement.

That is primarily because I don’t need the movement sensor (PIR), which by the way draws quite a lot of juice from the batteries. And I am running all my nodes on LiIon-Batteries that I took from old mobile-phones of mine, or from compact digital cameras.

But let’s get back to the intended topic:

DHT11 front

DHT11 front

I recently bought two cheap sensors, AOSONG AM2302 also known as DHT22 and a similar one from AOSONG called DHT11, both sporting a capacitive humidity sensor and a thermistor and some simple controlling electronics that give you the measured values with a defined protocol.

These sensors differ only by the range and precision of measurement for humidity and temperature. Generally speaking the DHT22 is the more precise one of both, and also the more expensive one.

And the good thing is that someone already developed a library. And this time around I got the library from ladyada and tried it with a JeeNode on a breadboard.

Luckily both sensors work quite good, and none of the restraints (precision, slowness) that the sensors have, are a problem for my intended use.

What I am now up against is the task of build some sort of plug to mount the DHT’s and from there on write some code to make the combination of JeeNode and DHTplug usable like a RoomNode. Hopefully with the same success in energy saving, low-power, and so on!

DHT11 sensor back

DHT11 sensor back
as you might see it has an operating voltage
from 3.3V up to 5V, great for low-power
operation on JeeNodes.

Continue to the second part of this post for a look at the Plug and the code for using it.



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