OLED display, 128x64, 0.96", SSD1306, I2C with PIC16F628A. Oled is driven by software (bit banging) I2C. Setting the room temperature by 2 buttons.
Output transistor is to drive a relay or directly 24VDC input to a central heating boiler. Hysteresis is 0.5 degree. Update of the temperature is every second.
Temperature range is -55 to 100 centigrade.