QTR-1RC Reflectance Sensor - Problem reading data with Arduino Mega

Other Hardware Sensors
1

Hi all,
I am trying to read the sensor values from a QTR-1RC Reflectance Sensor to an Arduino Mega.
I have been following instructions on
http://forum.pololu.com/viewtopic.php?f=6&t=3696&start=0&st=0&sk=t&sd=a&sid=90e60dca175a22c8f8d9c3c626220b12
but just can't seem to get it working.

I simplified the code to:

#include <PololuQTRSensors.h>

/* 5V = Vin
SENSOR_PIN = VOUT
GROUND = GROUND-Arduino[POWER]
*/
#define SENSOR_PIN 3
#define LED 13
PololuQTRSensorsRC qtr((unsigned char[]) {SENSOR_PIN}, 1, 2000);

unsigned int sensorValues[1];
unsigned long time;
void setup()
{
pinMode (LED, OUTPUT);
pinMode (SENSOR_PIN, INPUT);

Serial.begin(9600);
}

void loop()
{
qtr.read(sensorValues);
Serial.print(sensorValues[0]);
delay(50);
Serial.println();
}

But always just get the value "2000" in the serial monitor.

I am also including the photo of how I wired the sensor.

If anyone can point out what I'm doing wrong I'd be very thankful.

All the best
Frank

CIMG1988.jpg
CIMG1988.jpg3072×2304 944 KB

2

First off you need a resistor in line with that LED, you are endangering both the LED and the arduino. Yes they have that LED wrong on the Pololu site as well.

Next it looks like you have the wiring of the sensor wrong. It is hard to see but the marking on the sensor appears to show a ground where you have the sensor, check the wiring because it is hard to see.

3

Thanks for the message!
I think you are right and have now switched the black and the white cable.
But I still get the same "2000" result all the time.

Thanks a lot
Frank

4

You might have blown it. =(

Look with an electronic camera viewfinder, do you see one of the LEDs lit up?

The main problem is the use of the library you can't see what is going on.

5

Hello!

I tried it again with a new sensor that can't be broken.
I did everything as described above - but with the white and black cable switched.

Still I only get the value "2000" all the time in the serial monitor.....

Any ideas ?

Thanks!
Frank