With intense use, the CPU may heat up, especially if it is mounted without a heat sink. If 65 ° C is exceeded,one GPIO pin goes to 1 to control the power on of a fan.
pin 7: Orange Pi Zero 2
pin 12: Orange Pi One Plus
pin 7: Raspberry 4B
After 30s of inactivity, no more web client connected, radio signal processing stops, CPU temperature drops rapidly.
First of all. It is a PNP transistor in your schematics, while 2n2222 is npn. This scheme is not working. The pin 7th don’t go 0 on Orange pi after 65C
On the schematic, it’s a NPN . Over 65°C, the pin goes 1. It can take 30s to switch from 0 to 1 or 1 to 0.