情境
A home automation system uses an ESP8266 GPIO to control a 5V relay through an NPN transistor, with an SPDT switch to manually override the relay state.
這張圖裡有什麼
看懂背後的決策。
01
Use an NPN transistor (2N2222) as low-side switch for relay coil
02
Include flyback diode across coil to protect transistor
03
SPDT switch selects between MCU GPIO (Auto) and +5V (Manual On)
04
Relay contacts switch an AC lamp with fuse protection
Reusable for any ESP8266/ESP32 relay driver circuit where a manual override or test switch is needed.