UNO + HB100 + LCD

Hi guys. My name is Bernardo, from Argentina.

I am on a speed radar project for private neighborhoods.

The materials I use are:
-Arduino uno
-HB100 by limpkin
-LCD display 12x2
-Battery 12v 7ah

I have tried several codes, using libraries, or not. Inside the house it works, running or walking, but when I take it to the street, sometimes it works, sometimes it doesn’t. Is it a hardware or code problem? Or is the sensor not suitable for this project?

Code

#include <FreqPeriod.h>
#include <Wire.h>      // libreria de comunicacion por I2C
#include <LCD.h>      // libreria para funciones de LCD
#include <LiquidCrystal_I2C.h>    // libreria para LCD por I2C

LiquidCrystal_I2C lcd (0x27, 2, 1, 0, 4, 5, 6, 7); // DIR, E, RW, RS, D4, D5, D6, D7

double lfrq;
long int pp;

void setup() {
Serial.begin(9600);
  FreqPeriod::begin();
  lcd.setBacklightPin(3,POSITIVE);  // puerto P3 de PCF8574 como positivo
  lcd.setBacklight(HIGH);   // habilita iluminacion posterior de LCD
  lcd.begin(16, 2);     // 16 columnas por 2 lineas para LCD 1602A
  lcd.clear();      // limpia pantalla

  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 ");
  //lcd.setCursor(0,0);
  Serial.print(lfrq/19.49);
  Serial.println( "km/h");
  lcd.print(lfrq/19.49);
  lcd.print( "km/h");
  delay(200);
  lcd.clear(); 
}
}

I want it to work like in this video
And the code that Markus shares, I modified it to show on the display, it works running or walking (at a distance of 3 meters), but with cars it does not seem to work.

At that time I was with 9v batteries, now it is with 12v directly to arduino (I would be missing a stepdown)

What readings do You get when trying to radar measure on cars? What Readings do get when there is no car moving?

Using 12 volt instead of 9, check the temperature of the 5 volt regulator on the UNO.