Hi! I am trying to develop a speed measurement system based on the distance sensor VL53L0X. The idea is to set the sensor in one side of the object whose speed I want to measure. The object would move along a corridor with a number of protrusions, separated by equal distances of 20,0 cm (this distance is modifiable, but it should not be much greater than this, because the corridor would be too long!).
The sensor gives me back the distance measure, which -using an ''if'' function- I use as 0-1 to calculate the time consumed between consecutive protrusions. The distance and velocity measures appear on a screen.
I have been able to measure velocity, but at a very slow pace (no more than 0,2 m/s) that is not enough for my application.The distance measurement is accurate, but I guess the sensor is not good at calculating sudden changes at high speed (from 200 mm to 500 mm aprox. in less than a second). I suppose the problem has something to do with this, but I am not sure if it could also be related to the library I use and the variable that saves the distance value.
Has anyone tried to make a similar project with this sensor? Have you found these problems?
I would be very grateful if someone could help me with this.
I attach here a copy of my code.
#include <Wire.h>
#include <VL53L0X.h>
#include <MedianFilter.h>
#include <LiquidCrystal_I2C_AvrI2C.h>
VL53L0X sensor;
MedianFilter test(10, 0);
LiquidCrystal_I2C_AvrI2C lcd(0x27, 20, 4);
unsigned long timeBefore = 0; //Time reference to compare
unsigned long timeConsumed = 0;
int faraway=HIGH;
float speedmm=0; //Speed in mm/s
float distance=0.2; //distance between protrusions
float speedm=0; //speed in m/s
// Uncomment this line to use long range mode. This
// increases the sensitivity of the sensor and extends its
// potential range, but increases the likelihood of getting
// an inaccurate reading because of reflections from objects
// other than the intended target. It works best in dark
// conditions.
//
#define LONG_RANGE
// Uncomment ONE of these two lines to get
// - higher speed at the cost of lower accuracy OR
// - higher accuracy at the cost of lower speed
#define HIGH_SPEED
//
//#define HIGH_ACCURACY
void setup()
{
Serial.begin(9600);
Wire.begin();
sensor.init();
sensor.setTimeout(500);
lcd.begin();
lcd.backlight();
lcd.setCursor(0, 0);
lcd.print("WELCOME");
#if defined LONG_RANGE
// // lower the return signal rate limit (default is 0.25 MCPS)
// sensor.setSignalRateLimit(0.1);
// // increase laser pulse periods (defaults are 14 and 10 PCLKs)
// sensor.setVcselPulsePeriod(VL53L0X::VcselPeriodPreRange, 18);
// sensor.setVcselPulsePeriod(VL53L0X::VcselPeriodFinalRange, 14);
#endif
//
#if defined HIGH_SPEED
// // reduce timing budget to 20 ms (default is about 33 ms)
// sensor.setMeasurementTimingBudget(20000);
#elif defined HIGH_ACCURACY
// // increase timing budget to 200 ms
// sensor.setMeasurementTimingBudget(200000);
#endif
// Clear the buffer.
}
void loop()
{
int o,r = sensor.readRangeSingleMillimeters();
test.in( r );
o = test.out();
if (sensor.timeoutOccurred()) { Serial.print(" TIMEOUT"); }
lcd.setCursor(0, 0);
lcd.print("DISTANCE ");
lcd.setCursor(0, 1);
lcd.print(o);
if(o>500){ //No-protrusion
lcd.setCursor(0, 2);
lcd.print("FARAWAY... ");
faraway=1;
}
if(o<500 and faraway==1){ //Protrusion
timeConsumed = (millis()-timeBefore); //It calculates the time between protrusions
lcd.setCursor(0, 2);
lcd.print("NEAR... ");
faraway=0;
speedmm=distance*1000000/timeConsumed;
speedm=speedmm/1000;
lcd.setCursor(0, 3);
lcd.print(speedmm);
Serial.print(speedmm);
Serial.println();
timeBefore=millis(); //Time actualization
}
}
. Has anyone done some test with this sensor and could help me to get better conditions for measurement? Do you have more ideas of what could be going wrong?