HC-SR04 quick wiring
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Uno: VCC 5V, GND GND, TRIG 7, ECHO 8
ESP32: VCC 5V(VIN), GND GND, TRIG 5, ECHO via 1k/2k divider to 18
ESP8266: VCC 5V(VU), GND GND, TRIG 5(D1), ECHO via divider to 4(D2)

DHT11: VCC 3V3/5V, DATA GPIO + 10k pull-up, GND GND
LDR: VCC -- LDR -- A* -- 10k -- GND
Button: GPIO -- BTN -- GND (INPUT_PULLUP)
PIR: VCC 5V, OUT GPIO, GND GND
LED: GPIO -- 220R -- LED -- GND
Relay module: VCC 5V, GND GND, IN GPIO (set polarity flag)
