R7
Resistance
120 Ω
Saillor Hat SH-ESP32
R1
Resistance
200000 Ω
Over-temp alarm.
External 5V power source for alarm buzzer.
+5 V
R3
Resistance
330 Ω
Transistor and relay to drive alarm buzzer.
Voltage divider for Thermistor.
RC circuit to convert PWM signal to analogue.
Buzzer
1N4007
U2
Thermistor
Optocoupler
2N2222
Relay