Interacting with a motion sensor unit

The motion sensor unit detects an object or a human’s emitted heat energy using a passive pyroelectric IR detector. The device is passive based on no external power supply being needed to operate the detector. The pyroelectric crystal serves as the heat or IR detection element within the motion unit. When the pyroelectric crystal detects heat or IR, the surface of the crystal produces an electric charge. This electric charge is sent to an electronic switch that controls a visual signaling device, such as an LED. Figure 2.38 shows the M5Stack motion sensor unit:

Figure 2.38 – An M5Stack motion sensor unit

Note

The change in a material’s surface charge in response to temperature variations is known as the pyroelectric effect.

When the motion sensor unit detects an IR source, the device’s output pin turns on. The output signal stays on for approximately 2 seconds. When the IR source is...