A light that comes on for movement, but only when it's dark. A PIR sensor watches for motion, a light-dependent resistor decides how sensitive to be, a potentiometer sets the threshold, and a servo and an LCD show what the system is doing.
How it decides
In darkness the threshold drops so the faintest movement counts; in daylight it rises so the light stays off. Motion, scaled by the potentiometer, is compared with the threshold: above it, the LED lights and the servo swings its latch to 125°; below it, the LED goes out and the latch returns to 35°. When the potentiometer is set below the threshold, the LCD reads SYSTEM IS OFF.
- PIRIs anything moving?
- LDRHow dark is it?
- ThresholdSet by the potentiometer
- RespondLED, latch at 125°, LCD