SIMPLE CENTRAL HEATING CONTROLLER

Device is perfect for very simple systems that have one common pump for heaters and heater exchanger. In base version ventilator is without software, becouse in there's no ventilator in that system. Additional output with tiac make easy to modify program and add regulation of ventilator. Controller have got two modes:
- summer when it's mostly responsible for warming water and pump works only when temperature on stove is higher than on exchanger,
- winter when pump work always when temperature on stove is highest then minimum.
Extra function on the controller is temperature measure on stove, boiler, balance tank, and house. You can set the minimum temperature, alarm temperature and change work mode.
Schelude:

Brain of controller is microcontroller U1 (ATMega8) with quartz resonator X1(16MHz) and condensers C1, C2 (both 22pF ). Condensers C3 (220uF) and C4 (100nF) filtrate power voltage, that should goes to power pin (ARK2) from second board. Potentiometer P1 (10k) allow to regulate display contrast W1(LCD 2x16).Thanks to transistor T1(BC556) and resistor R2(3,3k) we have possibility to turn on LCD backlight. Resistor R1 (47R) cut voltage at diodes. Buzzer BUZ1 (5V) is a alarm. Alarm starts thanks to transistor T2 (BC556) and resistors R3 (3,3k) and R4 (3,3k), when temperature is higher then limit that we set.
S1...S3 buttons works as a keyboard.

Executive chipset

In executive chipset we have voltage stabilizator U1 with condensers C1 and C2. To power connector (ARK) we need to plug 7-15V. As a execuitev elements we have triacs TR1 and TR2, resistors R2 R3 R5 R6. As a overloading secure we have varistors WR1 and WR2. A guard against shorting is F1 (2A) fuse. TRO1 (ARK) and TRO2 (ARK) are voltage output for pump and ventilator. Optotriacs OPT1 (MOC3041) and OPT2 (MOC3041) make separation between high voltage circuit and low voltage circuit.

Full description at:
https://www.elektroda.pl/rtvforum/topic1476530.html?sid=cfcc1fc45329ee3012e116b08080d43f