Gas boilers are usually equipped with a simple sort of controlling element, but they regulate the amount of heating by measuring the water temperature inside the system. Without a proper room thermostat, that works on the principle of measuring the air temperature, is actually a waste of energy.
This project offers a very simple and cost efficient solution for that.
Hardware
The heart of the unit is an 8 bit PIC16F74 microcontroller from Microchip.
It’s main task is to constantly monitor the room temperature trough a 1–wire digital thermometer IC, a DS1820 from Maxim, and to switch a relay on or off, that controls the gas boiler accordingly.
The system also features a color LCD, which was removed from an old mobile phone, a few LED’s, an LDR sensor for night mode and a couple of pushbuttons.
For correct operation of the LCD, a supply voltage of 2.9V is needed. I’ve used an LM317L voltage regulator and two resistors to achive this. For data and control lines, a few simple two resistor voltage dividers were used.
For more detail: Room thermostat with colour LCD
