Thursday, February 7, 2013

Fan controller

As mentioned in the previous post, I am busy with changing a radiator here in the house, and, as part of my investigations into heat distribution efficiency and space efficiency, I decided to try a radiator built in the ceiling with forced air circulation.

This will be placed in the bedroom, in the ceiling, so out of sight, apart from the ventilation grills, in the attic.

The radiator receives the heat from the standard hot water circulation system, and uses a ventilator fan to take the heat to the room.

This particular unit has a 24V DC motor, whose speed is controlled by a 0V to 10V signal, so, like I mentioned before, I built an amplifier which takes a 0 to 3.3V filtered PWM JeeNode output and multiplies it by 3, giving me a nice 0-9.9V. Here is the schematic, made using Fritzing:

It works, a basic test with a very slow sweeping output turns the motor on slowly, ramping it up to maximum speed, and back again to off.
The controller in the JeeNode will read the input and output temperatures using a pair of good old DS18B20's, and controlling the speed accordingly. I am still developing the algorithm for that (will certainly pass by some sort of PID controller).
I don't really plan on using the JeeNode radio for the control part, but will certainly be feeding back statistics later on!
The regulation of the water will be by means of the FHT8V which has now been serving in the room for the last 5 years or so!

This weekend I'll disconnect the current radiator, which takes a huge amount of space in front of the windows, and start the process of assembling the new one. We'll move to a spare room for thermal confort!!