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Topic: Speed Radar Questions (Read 348 times) previous topic - next topic

mherupineda

Hi, I'm new here  :) i had a small project regarding measuring the speed of vehicles so i had to create a speed radar just like those speed radar signs on the road. What i'm doing now is creating a speed radar circuit which is for experimentation only. I had used a GH-100 Microwave Doppler Sensor and had able to interfaced it on arduino using the frequency library.

What i want to ask for those who had created or experienced how the speed radar works is that, can the speed radar detect a car which is behind it (even its not on its cone detecting range)? And if it detects the speed of a car that is reversing towards the back of the speed radar?

Example, we have a road and it has two (2) directions which is x and y, let's say x-direction is towards east and y-direction is towards west. Theres a speed radar sign perpendicular to the road and it is facing on x-direction (east) meaning it now measures the speed of cars coming from x-direction going y-direction.

My question means, Can the speed radar detect the speed of the car that is coming from the y-direction (west) going x-direction (east)? And can speed radar detect the speed of the car that is in reverse-mode coming from y-direction going x-direction?



I hope you can help me. React please if you had an idea with these. Thank you very much.

robtillaart

> can the speed radar detect a car which is behind it (even its not on its cone detecting range)?
No,

> And if it detects the speed of a car that is reversing towards the back of the speed radar?
No,

>  Can the speed radar detect the speed of the car that is coming from the y-direction (west) going x-direction (east)?
yes

> And can speed radar detect the speed of the car that is in reverse-mode coming from y-direction going x-direction?
yes

but as the answers above will probably trigger more questions,
please study the theory how Doppler radar works here - https://en.wikipedia.org/wiki/Doppler_radar

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

mherupineda

> And if it detects the speed of a car that is reversing towards the back of the speed radar?
No,

> And can speed radar detect the speed of the car that is in reverse-mode coming from y-direction going x-direction?
yes

but as the answers above will probably trigger more questions,
please study the theory how Doppler radar works here - https://en.wikipedia.org/wiki/Doppler_radar


Hi Sir,


      Thank you very much for the reply, i had already study the theory of how Doppler radar works that's why I'm confused on the output of the sensor i had made. The circuit i had made was the example on its datasheet which is a continuous wave circuit and my code on the arduino is like this:

Code: [Select]


#include <FreqMeasure.h>

 int count=0;
 double sum=0;
 
void setup() {

 Serial.begin(9600);
 FreqMeasure.begin();
 Serial.println("Frequency Read Begin");

}


void loop() {

   if (FreqMeasure.available()) {
      
   sum = sum + FreqMeasure.read();
   count = count + 1;
  
       if (count > 30) {          // average 30 readings together
    
           float frequency = FreqMeasure.countToFrequency(sum / count);
          
           float speedValue = frequency / 19.49;            // from the formula Fd = 2V(ftarget/c)cosTheta
                                                                          // where V(km/h) = Fd/19.49 and V(mi/h) = Fd/31.36
           if (speedValue < 1.00) {
      
                Serial.print(frequency);
                Serial.print(" Hz  ");
      
                speedValue = 0.00;
      
                Serial.print(speedValue);
                Serial.print(" kph ");

           } else {
      
                Serial.print(frequency);
                Serial.print(" Hz  ");
                Serial.print(speedValue);
                Serial.print(" kph ");
      
           }
        }
    
    sum = 0;
    count = 0;

    }
}



      The output i had after seems fine (though i had yet to buy a tuning fork) when i applied it practically on the road, when theres a car in moving in reverse towards the back of my sensor, it sense a lot of frequency, greater than the frequency of a moving car heading towards the front of my sensor (detecting range of the sensor).

       i had search studies but what i experience seem hadn't happened on others (that's why i even like to see a true speed radar on the road, and test some activities to see output. Dumb luck but theres no any speed radar on our area). Any explanation sir?

robtillaart

do you have a link to the datasheet of the GH-100 Microwave Doppler Sensor ?
Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

mherupineda

#4
Feb 13, 2016, 07:08 am Last Edit: Feb 13, 2016, 09:39 am by mherupineda
do you have a link to the datasheet of the GH-100 Microwave Doppler Sensor ?
thank you for the reply, http://pub.ucpros.com/download/GH100Datasheet.pdf?osCsid=vs1q4b4cdvohrm5i2ls257ts80 here's the datasheet link sir.

MarkT

#5
Feb 13, 2016, 12:36 pm Last Edit: Feb 13, 2016, 12:38 pm by MarkT
Doppler radar cannot sense forwards v. backwards, only the absolute value of the component of velocity
along the light-of-sight.  Remember than all metal objects reflect radio waves and radar works most reliably
in open terrain with no radio-reflecting surfaces other than the vehicle you are measuring.  You would expect
erroneous behaviour in a crowded urban environment for instance.

The other thing is the radar gun must be stationary during a measurement, you mustn't move it
or you'll get lots of artifacts from the speckle pattern.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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