here is an old project i did in early 2005. it’s a basic stamp based thermostat to heat an epoxy storage cabinet. i use a lot of expensive epoxy for this project, and it needs to stay above a certain temperature to be usable. it uses an incandescent light bulb and small fan to keep it above 80 degrees F.
i could have used an off the shelf thermostat from home depot, but i was surprised how much they were. i also wanted to add some features, like a photocell to detect when the bulb burns out and sound an alarm.
it’s built on a basic stamp 1 project board. it uses a ds1620 temp sensor, triac solid state relay, and 12v pc fan with photocell. if the reading of the ds1620 drops below 80 deg, the bs1 lights up the opto-isoloator on the triac, this powers the 120v light bulb. a 12v dc fan helps circulate the air, and is turned on at the same time with a simple switching transistor. when the temp hits 95 deg, the bs1 turns off the light bulb and fan. a photocell on the fan detects if the bulb is burnt out and the bs1 sends an audible alarm to a piezo speaker.