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