Motion Detector

Snap Circuits® uses electronic blocks that snap onto a base grid to build different circuits. These blocks have different colors and numbers on them so that you can easily identify them. Build the circuit shown by placing all the parts with a black 1 next to them on the clear base grid first. Then, assemble parts marked with a 2. Then, assemble the part marked with a 3. Install three (3) “AA” batteries (not included) into the battery holder (B3). Place the base grid into the blue stand (with either the battery holder or the NPN transistor (Q2) closest to the stand) and carefully stand it up. Position it near the edge of a table, facing across a room.

Turn on the slide switch (S1). The color LED (D8) lights and the horn (W1) sounds for a few seconds on start-up, and then whenever the circuit detects motion in the room.

This circuit will work in the dark, but be careful not to hurt yourself moving around a room in the dark.