How do I create a timer? (continued below)

Projects Programming
1

How do I create a timer to time how long the wheels are moving forward before they are stopped by the ultrasonic distance sensor? Then, I would like to store that amount of time in a variable to be used later.

const int trigPin = A3; //Distance Sensor
const int echoPin = A2;
const int drillPos = 4; //Drill Motor
const int drillNeg = 5;
const int rightFrontPos = 12; //Right Wheels
const int rightFrontNeg = 13;
const int rightBackPos = 10;
const int rightBackNeg = 11;
const int leftBackPos = 8; //Left Wheels
const int leftBackNeg = 9;
const int leftFrontPos = 6;
const int leftFrontNeg = 7;
const int sensorPin = A0; //Temperature Sensor
const float baselineTemp = 25.0;
const int redColor = 3; //Red color
const int greenColor = 2; //Green color
float duration;
float distance;

void setup() {
  pinMode(trigPin, OUTPUT);
  pinMode(echoPin, INPUT);
  pinMode(drillPos, OUTPUT);
  pinMode(drillNeg, OUTPUT);
  pinMode(rightFrontPos, OUTPUT);
  pinMode(rightFrontNeg, OUTPUT);
  pinMode(rightBackPos, OUTPUT);
  pinMode(rightBackNeg, OUTPUT);
  pinMode(leftFrontPos, OUTPUT);
  pinMode(leftFrontNeg, OUTPUT);
  pinMode(leftBackPos, OUTPUT);
  pinMode(leftBackNeg, OUTPUT);
  pinMode(redColor, OUTPUT);
  pinMode(greenColor, OUTPUT);
  Serial.begin(9600);
}

void loop() {
  digitalWrite(trigPin, LOW);
  delayMicroseconds(2);
  digitalWrite(trigPin, HIGH);
  delayMicroseconds(10);
  digitalWrite(trigPin, LOW);
  duration = pulseIn(echoPin, HIGH);
  distance = (duration / 2) / 74;
  Serial.print("Distance in inches: ");
  Serial.println(distance);

  if (distance > 100) {
    analogWrite(greenColor, 255); //Set light to green
    analogWrite(redColor, 0);

    digitalWrite(leftFrontPos, HIGH); //Wheels Spin Forward
    digitalWrite(leftFrontNeg, LOW);
    digitalWrite(leftBackPos, HIGH);
    digitalWrite(leftBackNeg, LOW);
    digitalWrite(rightFrontPos, HIGH);
    digitalWrite(rightFrontNeg, LOW);
    digitalWrite(rightBackPos, HIGH);
    digitalWrite(rightBackNeg, LOW);
  } else {
    //Stop all motors
    for (int motorPin = 6; motorPin <=13; motorPin++) {
      digitalWrite(motorPin, LOW);
    }
    delay(1000); //Delay for one second (adjust as needed)

    //Start the drill motor
    digitalWrite(drillPos, HIGH);
    digitalWrite(drillNeg, LOW);

    int sensorVal = analogRead(sensorPin);
    Serial.print("Sensor Value: ");
    Serial.print(sensorVal);

    //Convert the ADC Reading to voltage
    float voltage = (sensorVal / 1024.0) * 5.0;
    Serial.print(", Volts: ");
    Serial.print(voltage);

    Serial.print(", degrees C: ");
    //Convert the voltage to temperature in degrees Celcius
    float temperature = (voltage - 0.5) * 100;
    Serial.println(temperature);
    
    if (temperature <= baselineTemp) {
      //Continue spinning the drill motor
      digitalWrite(drillPos, HIGH);
      digitalWrite(drillNeg, LOW);
    }
    else {
      //Stop the drill motor
      digitalWrite(drillPos, LOW);
      digitalWrite(drillNeg, LOW);
      
      //Set RGB Light to Red
      analogWrite(greenColor, 0);
      analogWrite(redColor, 255);
      
      //Reverse the direction of all wheels
      digitalWrite(rightFrontPos, LOW);
      digitalWrite(rightFrontNeg, HIGH);
      digitalWrite(rightBackPos, LOW);
      digitalWrite(rightBackNeg, HIGH);
      digitalWrite(leftFrontPos, LOW);
      digitalWrite(leftFrontNeg, HIGH);
      digitalWrite(leftBackPos, LOW);
      digitalWrite(leftBackNeg, HIGH);
      
      delay(3000);
      
      //Stop all motors
      for (int motorPin = 6; motorPin <= 13; motorPin++) {
        digitalWrite(motorPin, LOW);
      }
      //Stop the wheels in place for 10 minutes
      delay(600000); 
    }
  }
}
2

Welcome to the forum

Save the value of millis() when the wheels start moving forward.

Save the value of millis() when the wheels stop moving forward.

Subtract one value from the other and you know how long the wheels have been moving forward. Put the value in a variable for use later

1 Like
3

A couple of tips

This wont be super acccurate, as your just timing how long the motor has run for. If theres varying loads on the motor the rpms will be lower.

Also try and get rid of the delays. It might work for your current case but once your adding extra functionality to your project the delays will freeze your program. Look up Blink without delay and state machines

4

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