Measure speed with two photoresistors

In this project I show you a simple way to measure the speed of objects passing by.

May 25, 2022

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speed

velocity

photoresitor

Components and supplies

Arduino Mega 2560

Resistor 10k ohm

Photo resistor

Project description

Code

arduino

1void setup(){
2  Serial.begin(9600);
3  delay(100);
4}
5
6
7void  loop(){
8  int x = analogRead(A0);
9  delayMicroseconds(100);
10  if(abs(analogRead(A0)  - x) > 2){
11    unsigned long t = micros();
12    while(1){
13      x = analogRead(A1);
14      delayMicroseconds(100);
15      if(abs(analogRead(A1) - x) > 2){
16        Serial.print(360000.0/(micros()  - t));
17        Serial.println(" km/h");
18        delay(500);
19        break;
20      }
21    }
22  }
23}

void setup(){
  Serial.begin(9600);
  delay(100);
}


void  loop(){
  int x = analogRead(A0);
  delayMicroseconds(100);
  if(abs(analogRead(A0)  - x) > 2){
    unsigned long t = micros();
    while(1){
      x = analogRead(A1);
      delayMicroseconds(100);
      if(abs(analogRead(A1) - x) > 2){
        Serial.print(360000.0/(micros()  - t));
        Serial.println(" km/h");
        delay(500);
        break;
      }
    }
  }
}

Downloadable files

Schematics

Connect everything as shown in this picture. It is very important that the two photoresistors are 10cm apart from each other. Otherwise you will get wrong speed measurements.

Schematics

Connect everything as shown in this picture. It is very important that the two photoresistors are 10cm apart from each other. Otherwise you will get wrong speed measurements.

Schematics

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galoebn

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