ok i looked at the code and it seem in general you can set the setpoint with the buttons... the code incorporates a small hysteresis so the heating element does't turn on and off to fast... there are some logarithmic calculations done i guess it's because the thermistor is not linear... to tell you simply why not use a different approach? a made a thermostat for a spider terarrium for my friend once. it uses an LM35 sensor and a potentiometer for setting the setpoint (i used it so the setpoint is the same even if there is a power outtage). and everything is printed to an 2x16 lcd 