Hi, I am a novice in electronics. I am trying to follow a tutorial to build a toy car speed checker for my little brother (this one: HERE), but I am using arduino uno instead of adafruit feather since I have it already. the same IR sensors shown in the tutorial are not available where I live, so I am using 2 phototransistors to receiver IR beam. The code I used is this one:
#include <SPI.h>
#include <Wire.h>
#define SENSORPIN1 10 //Sensor 1 is on the right
#define SENSORPIN2 11 //Sensor 2 is on the left
long end_time; // When Sensor 2 is triggered
long start_time; // When Sensor 1 is triggered
long elapsed_time; // End time minus start time
float mph; // Speed calculated
int trigger1 = 0; // Sensor 1
int trigger2 = 0; // Sensor 2
int sensor1State; // Sensor 1 status
int sensor2State; // Sensor 2 status
void setup() {
Serial.begin(9600);
pinMode(SENSORPIN1, INPUT); // Sensor 1 as input
digitalWrite(SENSORPIN1, HIGH); // Turn on the pullup
pinMode(SENSORPIN2, INPUT); // Sensor 2 s input
digitalWrite(SENSORPIN2, HIGH); // Turn on the pullup
// by default, we'll generate the high voltage from the 3.3v line internally! (neat!)
}
// Function to determine speed
void speed()
{
// subtract end time from start time to get total time
elapsed_time = ((end_time - start_time));
// convert mm/s to mph
mph = ((106000 / elapsed_time) * 0.0022);
Serial.print(mph);
Serial.print("mph");
}
void loop() {
// Read the state of the IR sensor 1:
sensor1State = digitalRead(SENSORPIN1);
// See if IR beam of sensor 1 has been broken
if (sensor1State == LOW) {
// Check to make sure both sensors have not triggered
if (trigger1 == 0 && trigger2 == 0) {
// Save time when sensor 1 was triggered
start_time = millis();
// Prevent sensor 1 from triggering again
trigger1 = 1;
}
}
// Read the state of the IR sensor 2:
sensor2State = digitalRead(SENSORPIN2);
// See if IR beam of sensor 2 has been broken
if (sensor2State == LOW) {
// Check to make sure sensor 1 has triggered but not sensor2
if (trigger2 == 0 && trigger1 == 1) {
// Save time when sensor 2 was triggered
end_time = millis();
// Run speed function
speed();
// Prevent sensor 2 from triggering again
trigger2 = 1;
}
delay(1000);
// Reset both sensors
trigger1 = 0;
trigger2 = 0;
}
}
I have also tried to adapt the circuit as best as I can after a lot of research. I used 330 ohms resistors for IR transmitters, and 10K ohms for the IR phototransistors.
The changes I made to the code is deleting <Adafruit_GFX.h> and <Adafruit_SSD1306.h> libraries, and all the commands related to the screen display and replaced them with serial.print().
The problem is I cant get anything to show up on the serial monitor and now I have been stuck for 3 days. Did I make a mistake in wiring the circuit? or in changing the code?
