05.20
I’d put the attic fan controller on the back burner for awhile, but now that the long, wet, cold Connecticut spring is finally winding up, its time to get working on this again. As I write this, its approximately 85 degrees F in the living areas, and an attic fan will definitely help alleviate some of the heat seeping into the house.
I’ve been advocating using the Jeenodes to control this thing, and Jean Claude at Jeelabs has done some similar work, a thermostat for his reflow heater. Essentially implementing the P and D part of a Proportional Integral Derivative (PID) Controller, what he had to say is after the jump…
This is part 6 of my reflow controller series. Let’s see if we can get the reflow grill to a stable 150°C.
It’s not trivial: this grill has a slow startup time and a very noticeable lag in its response curve. Turning on the grill and turning it off at 150° is not the way to do it, since the stored heat will lead to a huge overshoot.
The proper way to do this is to use a PID control algorithm. PID stands for Proportional Integral Derivative. It’ll be interesting to try that, but first I want to try something simpler (actually, it is still PID, but just P and D).
So its off to the code foundry to hammer out some bits, couple the code with the TMP-421 temperature sensor, and make it all call home. So watch this space for further details in the coming days.
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