Aga gas tap timer
We inherited an Aga when we moved into our house; it used to be coke fired but had been converted to gas. Generally speaking it's great and I enjoy cooking on it (and it heats our water for us) BUT it uses a lot of gas.
This scheme uses an arduino type microprocessor with a servo to turn the temperature control right down at night and during the day. The Aga takes about three hours to heat up or cool down but I reckon it must be saving quite a bit of gas (data to appear here when I have collected and analysed it!)
The sketch is basically a clock with two buttons (mode and setting) a short press on either increments and a long press sets to zero. Modes are:
hour, day, first_start, first_stop, second_start, second_stop, holiday_days, toggle_on_off. After adjusting anything the current values are saved in EEPROM. Power off or reset starts seconds and minutes from zero but loads everything else from EEPROM.
As well as the servo output I put in an extra digital output which switches a transistor on the ground side of the servo power supply. I put this in because the servo made a buzzing noise even when it wasn't really doing anything.