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Old 04-22-14, 03:45 PM   #29
Daox
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Lately, I've been having some issues with my thermal differential controller. The fans will turn on and off a LOT unless it is really hot up in the attic. What I believe is happening is there is noise on the long sensor wire run to the kitchen which makes the temperature signal bounce around. I originally had this problem, so I put a small capacitor on the wire and it seemed to work... for a while.

Now, I am going about doing it the right way. I am reprogramming the controller to filter out the noise on the lines. This will be a completely free fix and require no new hardware, no soldering, no physical changes at all. The fix is pretty simple. I take a bunch of sensor readings and average them. This isn't a super precision thing, so it'll work just fine.

I did some quick and dirty reprogramming last night where I took 5 temperature readings and did some very poor 'averaging' just as a quick test and it made it 90% better than before. The fans kicked in and stayed on until it got close to the differential set point. Then, it started to turn on and off a bit. Not much, but a little better programming should virtually eliminate it all. This also means that I'll be able to get more heat out of the system because the fans will be running full tilt versus on and off.

Anyway, I am finishing up the programming soon and I'll post the new code when I find that it works good. I'm thinking 10 temperature readings should work out great, and get a true average of them. This also will eliminate the need for the capacitor shown in the schematic making wiring a little easier.
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