In this project a Doppler radar motion sensor (type RCWL-0516) is applied to trigger an Arduino to light a LED. The LED stays on until a button is pressed. Normally this would be simple to achieve. The challenge here is that the motion detector has an OUT pin that, when the detector senses something, carries a signal for two full seconds. As the RCWL-0516 acts autonomously we need an Arduino to control the LED’s performance in software. A touch switch whose state is continuously monitored by the Arduino is used to turn the LED off. An 128*64 OLED presents visual information about the state of various parameters. Through this we have an Arduino version at hand of a stairway – basement – cupboard proximity lighting system.
Motion detection typically is the domain of security systems, car protection, lighting applications and wildlife photography. This type of detection can be accomplished in several ways, for instance with a passive infrared detector (PIR) that senses temperature changes in the body heat range. A completely different way to detect movement or displacement is through Doppler radar sensing. This can be helpful in situations where moving objects do not project a significant amount of heat (imagine a big cold blooded lizard, say a T-Rex, peeking around the corner or an electric car driving up your driveway).
Figure 1. RCWL-0516 breakout board. Shown is the upper surface with the electronic components, the ‘active’ face that must preferably be directed towards the area to be monitored. In the current project we need only pins VIN, OUT and GND. CDS is for day-night operation selection while the pin marked 3V3 is an auxiliary pin that continuously provides 3.3V power.