This might just be the fastest project I’ve ever done. Saturday morning I started the hardware build, by Saturday evening I had also begun the software. By Sunday afternoon I was halfway through. Sunday evening saw it 90% completed. Monday was finishing touches and adding some extras just because. Tuesday I finished it. This afternoon I installed it.
Some of the things that aren’t obvious in a still photo: The the block above the screen has two RGB LEDs behind it. These aren’t programmable, but one cycles through the colours slowly and the other does so quickly. Together they provide a sort of swirly multi-colour effect that I think is reminiscent of ST:ToS effects.
The red circle ‘red alert light’ is wired to the XBee’s RSSI so when the XBee receives a wireless command, the red light comes on for a few seconds.
The white gridded rectangle is the DHT22 sensor (temperature and humidity). I felt it would ‘blend in’ enough that it should be mounted right up front for all to see. The little black hole to the right of the DHT22 is for the light sensor.
Why is there a light sensor? Why not? Also: because I had an extra one laying around.
The screen display is mostly self-evident. Time, day, date. Heat/Cool. Run/Hold/Override. Target temp (small) and actual temp (large). Fan status (on/auto) and humidity.
The last line is EV (exposure value) and free memory. That’s 657 bytes. Not kB or MB, just bytes. It probably won’t ever change but it’s there just because there was space for it.
The following images have some more build details / information:
The sketch code, and a text file with lots of my design and build notes, can be downloaded here: Thermostat_3.zip