here's my setup;
wood stove with a blower in the back and a house fan in the ceiling above that shoots hot air into the 2nd floor. i needed to automate the fans ON/OFF, no need to run them when there is only cold air to more (in the winter). also, i wanted to have a CO detector, the sensor shield is about 3$ so why not? considering the fact that a complete detector is 30-50$ retail here.
- arduino pro mini (youll need a usb to serial if you dont have one)= 3$
- CO detector board MQ-7= 3$ (alarm trigger might need adjustment)
- relay board= 3$
- power supply 5volt=2$? (i used a 12volt one with a 317regulator)
- temperature probe DS18B20=2$
total cost: 10-15$
Arduino: i didnt have any female connector for the arduino, so i soldered directly on the pins, if you have any proper wire just plug them in instead. way nicer.
Temperature sensor: i made myself a bracket, it hold the sensor exactly where you want it, and at the same time adds a bit of mass to regulate the temperature reading. it help conteract the big fluctuation.
House wiring: it is a double plug with connecting links in between the two, i just removed the hot side one (keeping the neutral connected to both outlet) and connected my relay to the now independent socket. the power from the other side of the relay comes from the always HOT, of the switch. If you dont know what your doing STOP RIGHT HERE, this is not for you. DEATH IS IMMINENT!