Facing problem in interfacing HB100 doppler radar sensor with arduino

Using Arduino Sensors
1

Hello experts. Please help me as I am new at this platform. I am using arduino mega whose D8 pin is connected from amplifier output of HB100 doppler sensor. I have made this amplifier as per suggested in the HB100 datasheet. I found this code from somewhere in internet. But nothing is showing up in the serial monitor.
#include <FreqPeriod.h>

double lfrq;
long int pp;

void setup() {
Serial.begin(9600);
FreqPeriod::begin();
Serial.println('FreqPeriod Library Test');
}

void loop() {
pp = FreqPeriod::getPeriod();
if (pp) {
Serial.print ('period: ');
Serial.print(pp);
Serial.print(' 1/16us / frequency: ');

lfrq = 16000400.0 /pp;
Serial.print(lfrq);
Serial.print(' Hz ');
Serial.print(lfrq/31.36);
Serial.println( ' Mph ');
}
}

hb100 amplifier ckt.png

2

Please use code tags when posting code. For instructions, see "How to use this forum".

Please post a link to the "FreqPeriod" library, and to the HB100 data sheet.

This won't work. You need double quotes, not single quotes, around a character string.

    Serial.print(' 1/16us / frequency: ');
3

Yes double quotation is required and I have changed them accordingly.. Now the code looks like..

#include <FreqPeriod.h>

double lfrq;
long int pp;

void setup() {
Serial.begin(9600);
  FreqPeriod::begin();
  Serial.println("FreqPeriod Library Test");
}

void loop() {
  pp = FreqPeriod::getPeriod();
  if (pp) {
    Serial.print ("period: ");
    Serial.print(pp);
    Serial.print(" 1/16us / frequency: ");

  lfrq = 16000400.0 /pp;
  Serial.print(lfrq);
  Serial.print(" Hz ");
  Serial.print(lfrq/31.36);
  Serial.println( " Mph ");
}
}

Now in the serial monitor only showing 'FreqPeriod Library Test'
this is the link forfreqperiod library

HB100_Microwave_Sensor_Application_Note.pdf (149 KB)

HB100_Microwave_Sensor_Module_Datasheet.pdf (868 KB)

4

That would suggest that the mysterious library is not getting whatever input it might expect.

5

Why do you think the "FreqPeriod" library can be used with the HB100?

It seems to be intended for a completely different sensor, and for something called "Agro-Shield".

6

Actually I found it on a web page where they are using freqperiod library. Can you suggest me which library should I use in place of that and what modification should I do to the code accordingly?

7

No, because I have no idea what you want to do, or why.

For advice on how to get help from this forum, I recommend to read the "How to use this forum" psot.

8

I want to measure frequency and speed at the same time which will be printed on serial monitor as it can be seen from the code.

9

This code is working for me. But the frequency range is always showing 270 to 280Hz and speed 14km/hr to 16km/hr irrespective of any movement near hb100.. what is the reason

// Below: pin number for FOUT
#define PIN_NUMBER 47
// Below: number of samples for averaging
#define AVERAGE 4
// Below: define to use serial output with python script
//#define PYTHON_OUTPUT
unsigned int doppler_div = 19;
unsigned int samples[AVERAGE];
unsigned int x;

void setup() {
  Serial.begin(115200);
  pinMode(PIN_NUMBER, INPUT);
}

void loop() {
  noInterrupts();
  pulseIn(PIN_NUMBER, HIGH);
  unsigned int pulse_length = 0;
  for (x = 0; x < AVERAGE; x++)
  {
    pulse_length = pulseIn(PIN_NUMBER, HIGH); 
    pulse_length += pulseIn(PIN_NUMBER, LOW);    
    samples[x] =  pulse_length;
  }
  interrupts();

  // Check for consistency
  bool samples_ok = true;
  unsigned int nbPulsesTime = samples[0];
  for (x = 1; x < AVERAGE; x++)
  {
    nbPulsesTime += samples[x];
    if ((samples[x] > samples[0] * 2) || (samples[x] < samples[0] / 2))
    {
      samples_ok = false;
    }
  }

  if (samples_ok)
  {
    unsigned int Ttime = nbPulsesTime / AVERAGE;
    unsigned int Freq = 1000000 / Ttime;

    #ifdef PYTHON_OUTPUT
      Serial.write(Freq/doppler_div);
    #else
      //Serial.print(Ttime);
      Serial.print("\r\n");
      Serial.print(Freq);
      Serial.print("Hz : ");
      Serial.print(Freq/doppler_div);
      Serial.print("km/h\r\n");
    #endif
  }
  else
  {
    #ifndef PYTHON_OUTPUT
      Serial.print(".");
    #endif
  }
}