Introduction

The digital microwave sensor uses doppler radar to detect moving objects using microwaves. This differs from the method used by a regular infrared (IR) sensor as the microwave is sensitive to a variety of objects that can reflect it's wavefpr,, and its sensor readings are not affected by ambient temperatures. This type of sensor is widely used in industrial, transportation and civil applications such as measuring a vehicle's speed, measuring liquid levels, automatic door motion detection, automatic washing, production line material detection, car reversing sensors, etc. The microwave detection method has the following advantages compared with other detection methods:

  1. Able to detect objects without physical contact
  2. Readings not affected by temperature, humidity, noise, air, dust or light - suitable for harsh environments
  3. Strong resistance to radio frequency interference
  4. Low output, not harmful to the human body
  5. Microwaves have a wide detection range and velocity equal to the speed of light
  6. Supports non-life-class object detection

Specification

Board Overview

Antenna Description

<File:SEN0192-002.png>

Signal Processing

The following diagram demonstrates the working principle of the sensor module. It works by amplifying a tiny signal which is received by the microwave sensor, and then through the comparison circuit it converts the signal into a square signal with a digital output of 0 or 1 which an Arduino or other micro controller can easily handle. <File:SEN0192-001.png>

Signal Detection Range

Detection Angle: The angle of detection is 72 degrees with the antenna in a parallel direction (azimuth) The vertical (pitch) direction of the antenna is 36 degrees. <File:SEN0192-003.png>

Install

Microwaves can penetrate through walls. So sometimes it has inaccuracies when microwaves penetrate through outside walls and detect moving objects in non-target areas. Be sure to choose an installation location to avoid this!

<File:SEN0192-004.png>

Indicators and Output Status

When the microwave sensor does not detect moving objects, the indicator LED remains off. When the sensor detects moving objects, the LED will turn on and the output level will be change from HIGH to LOW. The LED will automatically turn off about after 0.5s and the output level will change from LOW to HIGH. If the microwave sensor detects continuously moving objects the LED will keep flashing on and off. The output level will fluctuate between HIGH and LOW until the object stops moving.

Distance Adjustment

The microwave sensor has a distance range of 2-16m. The detection distance can be adjusted using the potentiometer. If it is turned in the direction on MIN, the detection distance decreases. If it is turned in the opposite direction, the range increases.

Comparison with IR Sensor

Microwave Sensor IR Sensor
Trigger Mode Movement Infrared Reflection
Temperature Influence No Influence Over 40 degrees C can inhibit function
Object Penetration Able to penetrate any non-metallic object Unable to penetrate
Ambient Environmental Requirements No requirements Dusty or brightly lit environments can inhibit function
Working Life more than 100,000 hours about 1000 hours
Stability Very reliable and stable Induction distance will shorten over time

Tutorial

Requirements

Connection Diagram

SEN0192-CON.png

NOTE: Align the antenna surface towards the area you need to detect.

NOTE: The sensor can be adjusted continuously within the range of 2-16m. Turn the potentiometer in the direction of MIN and the detection range decreases. Turn the potentiometer in the opposite direction and the detection range increases.

Sample Code

Please download MsTimer2 library first. Here is tutorial about Library installation.

#include <MsTimer2.h>           //Timer interrupt function library
int pbIn = 0;                    // Define interrupt 0 that is digital pin 2
int ledOut = 13;                 // Define the indicator LED pin digital pin 13
int number=0;                    //Interrupt times
volatile int state = LOW;         // Defines the indicator LED state, the default is not bright

void setup()
{
     Serial.begin(9600);
     pinMode(ledOut, OUTPUT);//
     attachInterrupt(pbIn, stateChange, FALLING); // Set the interrupt function, interrupt pin is digital pin D2, interrupt service function is stateChange (), when the D2 power change from high to low , the trigger interrupt.
     MsTimer2::set(1000, Handle); // Set the timer interrupt function, running once Handle() function per 1000ms
     MsTimer2::start();//Start timer interrupt function

}

void loop()
{
Serial.println(number); // Printing the number of times of interruption, which is convenient for debugging.
    delay(1);
    if(state == HIGH)  //When a moving object is detected, the ledout is automatically closed after the light 2S, the next trigger can be carried out, and No need to reset. Convenient debugging.
    {
        delay(2000);
        state = LOW;
        digitalWrite(ledOut, state);    //turn off led
    }

 }


void stateChange()  //Interrupt service function
{
  number++;  //Interrupted once, the number + 1

}

void Handle()   //Timer service function
{
    if(number>1)  //If in the set of the interrupt time the number more than 1 times, then means have detect moving objects,This value can be adjusted according to the actual situation, which is equivalent to adjust the threshold of detection speed of moving objects.
         {
                   state = HIGH;
                   digitalWrite(ledOut, state);    //light led
                   number=0;   //Cleare the number, so that it does not affect the next trigger
         }
        else
              number=0;   //If in the setting of the interrupt time, the number of the interrupt is not reached the threshold value, it is not detected the moving objects, Cleare the number.
}

FAQ

Q&A Some general Arduino Problems/FAQ/Tips
A For any questions, advice or cool ideas to share, please visit the DFRobot Forum.

More Documents

DFshopping_car1.png Get Digital Microwave Sensor (Motion Detection) from DFRobot Store or DFRobot Distributor.

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