There is also a video on YouTube for this article: Arduino Motion Radar

The Doppler radar module for Arduino can detect speeds and movements. Because there are many different radar modules on the market, this guide and library may not be compatible. This module has a voltage of 5 volts and relays the data from the radar with analog voltage to the Arduino. Radar modules are extremely sensitive, so a stable power supply is very important. The 5V USB power supply from the computer is not particularly clean, but is sufficient for test purposes. If the sensitivity of the module can be adjusted, the potentiometer should be turned into the first quarter.

How the doppler radar module works

This AMP 165 doppler radar sensor is from Weidmann electronics and has a controllable gain. The module emits radio waves and evaluates the received signals. If a movement is detected, the module begins to generate voltage differences at the analog output. Depending on the sensitivity, the signals are different, so the tolerance must be specified as a percentage when using the library. The graph represents a detected movement in the form of a voltage difference at the analog input.

#include <Radar.h>

Radar radar(A5); //Radarmodule input at A5

void setup()
{
  Serial.begin(9600);
  radar.settolerance(10); //Set the tolerance from 0 to 100 percent
}

void loop()
{
  radar.measure(); //Read value from radar
  int radarvalue = radar.rtv(); //Get value (0 or 1)
  if(radarvalue == 1){
  Serial.println("Motion detected"); 
  }else{
  Serial.println("No motion"); 
  }
  delay(50);
}