We have a 13'x10' room that was a screened in porch, until I enclosed it with windows. I'm putting a drier vent in one wall, without the flapper and with finer screen, and a 4" duct fan from the ceiling into the attic. I'll have flappers on the inside of both of those. So Drier vent gets air from the cooler side of the house and the duct fan will push the hot air into the attic.
What I want to make is a circuit that measures inside and outside temps. It will activate when two conditions are met:
1 - Inside air temp is above a certain level (comfort zone or 66-75 F, 18-23 C)
2 - Outside air temp is lower than inside temp.
I'm fine with a +/- 5 degrees F (3 degrees C?) on each of these measurements. I'm wondering if I can get there with fairly cheap sensors (thermistor or similar).
Seems like if I use the same sensor, then I have a differential amp with each other and a differential for inside with a setting.
I do have a couple Maxim chips for thermocouples, but it feels like overkill for this.
Can I get close to accuracy I want without going higher tech. Or has anyone seen something that can be adapted to this on the cheap. I'm seeing + $200 units for process control, when I look at differential temp controllers.