Hook up esp32 and QTR-MD-08RC Reflectance Sensor Array


As i searched a lot this information, i share here my wiring cables between esp32 devkit and QTR-08RC :slight_smile:

QTR Gpio Esp32
1 12
3 14
5 4
7 16
9 17
11 5
13 18
15 19
VCC 5.5v

What i did not undestand is the CTRL pin : it seems that it does not have effect on IR led (can’t see them through camera although i can see other remote controls…)

If anyone can share this info, could be great :slight_smile:

I also put a led on Gpio13 (i do not have a builtin led) to see when calibrating is starting and finishing

The example code is slightly modified as below:

#include <QTRSensors.h>

QTRSensors qtr;

const uint8_t SensorCount = 8;
uint16_t sensorValues[SensorCount];

void setup()
// configure the sensors
qtr.setSensorPins((const uint8_t){12, 14, 4, 16, 17, 5, 18, 19}, SensorCount);


void loop()
// read raw sensor values

// print the sensor values as numbers from 0 to 2500, where 0 means maximum
// reflectance and 2500 means minimum reflectance
for (uint8_t i = 0; i < SensorCount; i++)



Other than defining an emitter control pin, it does not seem like your program is doing anything with that. By default, the QTR-MD-08RC board pulls the CTRL pin high turning on the emitters with the board’s default (full, 30mA) LED current.

If you want to try adjusting the LED emitter brightness, I recommend reviewing the Second-generation QTR/QTRX sensor array details section of the Pololu QTR Reflectance Sensor Application Note (particularly, the details under the “Emitter control” header) and using the appropriate functions form our Arduino library, like setDimmingLevel().

- Patrick