I just switched to this sensor, and believe I have wired it up correctly. When I read() the value, however, it usually returns 1024. If I press it very close to a piece of white paper, I can get a value as low as 947 or so. I’m confused because I thought 1023 was the highest value, and I am expecting lower values with white paper.
#define NUM_SENSORS 1 // number of sensors used
#define NUM_SAMPLES_PER_SENSOR 4 // average 4 analog samples per sensor reading
#define EMITTER_PIN QTR_NO_EMITTER_PIN // emitter is controlled by digital pin 2
// sensors 0 through 5 are connected to analog inputs 0 through 5, respectively
QTRSensorsAnalog qtra((unsigned char[]) {0},
NUM_SENSORS, NUM_SAMPLES_PER_SENSOR, EMITTER_PIN);
unsigned int sensorValues[NUM_SENSORS];
void setup()
{
delay(500);
// TURN ON PINS FOR QTR SENSOR
pinMode(13, OUTPUT);
digitalWrite(13, LOW);
for (int i = 0; i < 400; i++) // make the calibration take about 10 seconds
{
qtra.calibrate(); // reads all sensors 10 times at 2.5 ms per six sensors (i.e. ~25 ms per call)
}
// print the calibration minimum values measured when emitters were on
Serial.begin(9600);
for (int i = 0; i < NUM_SENSORS; i++)
{
Serial.print(qtra.calibratedMinimumOn[i]);
Serial.print(' ');
}
Serial.println();
// print the calibration maximum values measured when emitters were on
for (int i = 0; i < NUM_SENSORS; i++)
{
Serial.print(qtra.calibratedMaximumOn[i]);
Serial.print(' ');
}
Serial.println();
Serial.println();
delay(1000);
}
void loop()
{
qtra.read(sensorValues);
for (unsigned char i = 0; i < NUM_SENSORS; i++)
{
Serial.print(sensorValues[i]);
Serial.print('\t');
}
Serial.println(); // uncomment this line if you are using raw values
delay(250);
}
From your code, it looks like you are using the wrong QTR object for your QTRXL-HD-01A sensor; you should be using QTRDimmableAnalog, not QTRSensorsAnalog. You can find more details about the QTRDimmableAnalog class and its methods under the “QTRSensors Methods & Usage Notes” section in the Arduino Library for the Pololu QTR Reflectance Sensors.
I tested your code using an A-Star 32U4 Micro and was able to get meaningful readings. (I modified your code slightly by changing the ground connection from pin 13 to pin 12 and using the correct QTR object as mentioned in my previous post.)
I looked into your Adafruit Feather HUZZAH ESP8266 board further and found the following under the “Analog Pins” description of the “Pinouts” section in its tutorial:
You will need to add a voltage divider, since you’re powering the sensor board with 3.3V from your Feather board. However, I suspect the voltage divider would not work well because the sensor has a high output impedance, making it difficult to measure the signals accurately. You could try adding the voltage divider and see if it works fine for your setup and application. Otherwise, an RC sensor might work better.
#include <QTRSensors.h>
// This example is designed for use with six QTR-1A sensors or the first six sensors of a
// QTR-8A module. These reflectance sensors should be connected to analog inputs 0 to 5.
// The QTR-8A's emitter control pin (LEDON) can optionally be connected to digital pin 2,
// or you can leave it disconnected and change the EMITTER_PIN #define below from 2 to
// QTR_NO_EMITTER_PIN.
// The main loop of the example reads the raw sensor values (uncalibrated).
// You can test this by taping a piece of 3/4" black electrical tape to a piece of white
// paper and sliding the sensor across it. It prints the sensor values to the serial
// monitor as numbers from 0 (maximum reflectance) to 1023 (minimum reflectance).
#define NUM_SENSORS 1 // number of sensors used
#define NUM_SAMPLES_PER_SENSOR 4 // average 4 analog samples per sensor reading
#define EMITTER_PIN 3 // emitter is controlled by digital pin 2
// sensors 0 through 5 are connected to analog inputs 0 through 5, respectively
QTRDimmableAnalog qtra((unsigned char[]) {2},
NUM_SENSORS, NUM_SAMPLES_PER_SENSOR, EMITTER_PIN);
unsigned int sensorValues[NUM_SENSORS];
void setup()
{
delay(500);
Serial.begin(9600); // set the data rate in bits per second for serial data transmission
delay(1000);
}
void loop()
{
qtra.setDimmingLevel(0);
// read raw sensor values
qtra.read(sensorValues);
// print the sensor values as numbers from 0 to 1023, where 0 means maximum reflectance and
// 1023 means minimum reflectance
for (unsigned char i = 0; i < NUM_SENSORS; i++)
{
Serial.print(sensorValues[i]);
Serial.print('\t'); // tab to format the raw data into columns in the Serial monitor
Serial.print (analogRead(2));
}
Serial.println();
delay(250);
}
It sounds like the QTRXL-HD-01A sensor is working with your Adafruit Bluefruit Feather. If not, please elaborate on the issue you are having by providing more details (e.g. error messages, behavior descriptions, and printout of sensor values).
It doesn’t seem to be working correctly yet.
The IR led is indeed emitting, but I don’t get a large range of values returned. even when putting it against white and black paper.
#include <QTRSensors.h>
// This example is designed for use with six QTR-1A sensors or the first six sensors of a
// QTR-8A module. These reflectance sensors should be connected to analog inputs 0 to 5.
// The QTR-8A's emitter control pin (LEDON) can optionally be connected to digital pin 2,
// or you can leave it disconnected and change the EMITTER_PIN #define below from 2 to
// QTR_NO_EMITTER_PIN.
// The main loop of the example reads the raw sensor values (uncalibrated).
// You can test this by taping a piece of 3/4" black electrical tape to a piece of white
// paper and sliding the sensor across it. It prints the sensor values to the serial
// monitor as numbers from 0 (maximum reflectance) to 1023 (minimum reflectance).
#define NUM_SENSORS 1 // number of sensors used
#define NUM_SAMPLES_PER_SENSOR 4 // average 4 analog samples per sensor reading
#define EMITTER_PIN 3 // emitter is controlled by digital pin 2
// sensors 0 through 5 are connected to analog inputs 0 through 5, respectively
QTRDimmableAnalog qtra((unsigned char[]) {2},
NUM_SENSORS, NUM_SAMPLES_PER_SENSOR, EMITTER_PIN);
unsigned int sensorValues[NUM_SENSORS];
void setup()
{
delay(500);
Serial.begin(9600); // set the data rate in bits per second for serial data transmission
delay(1000);
}
void loop()
{
qtra.setDimmingLevel(0);
// read raw sensor values
qtra.read(sensorValues);
// print the sensor values as numbers from 0 to 1023, where 0 means maximum reflectance and
// 1023 means minimum reflectance
for (unsigned char i = 0; i < NUM_SENSORS; i++)
{
Serial.print(sensorValues[i]);
Serial.print('\t'); // tab to format the raw data into columns in the Serial monitor
Serial.print (analogRead(2));
}
Serial.println();
delay(250);
}
Can you replace 2 with A2 when initializing the qtra object and see if that fixes the problem? If not, can you post a video showing how you are testing the sensor and the distance you are holding the sensor from the paper? Also, can you post the values you get when putting the over the white and black paper?
