Week 09

This is my 9th week at FabAcademy. This week I have learnt about input devices. The assignment of the week consisted of:

group assignment: probe an input device’s analog levels and digital signals individual assignment: measure something: add a sensor to a microcontroller board that you have designed and read it

Group Assignment

This week we used the osciloscoper to check a load cell with a digital amplifier (checking both the analog native signal and digital transform) plus the digital pulses of a temperature & moisture sensor, check out the details here https://fabacademy.org/2025/labs/aindustriosa/week09.html

Individual Assignment

Regarding the individual assignment, I tested several input devices in a board designed and fabricated by me, in summary I tested the following input devices:

Button that modifies led behavior.
Temperature & moisture sensor.
Accelerometer.

In the folloiwing I explain the process till make the sensors working.

Regarding the first input device, the button, did not worked properly for me. I fabricated a PCB that allows for button input an used this input to modify the behavior of a led. My code reads as follows:

const int buttonPin = 8;
const int ledPin = 10;

int buttonState = 0;
int ledDelay = 1000;

void setup() {
  Serial.begin(9600);
  pinMode(ledPin, OUTPUT);
  pinMode(buttonPin, INPUT);
}

void loop() {
  buttonState = digitalRead(buttonPin);

  // Ajustar el retardo según el estado del botón
  if (buttonState == HIGH) {
    ledDelay = 100;
    Serial.println("Botón pulsado");
  } else {
    ledDelay = 1000;
    Serial.println("Botón no pulsado");
  }

  // Control del LED
  digitalWrite(ledPin, HIGH);
  delay(ledDelay);
  digitalWrite(ledPin, LOW);
  delay(ledDelay);
}

Altough the code seems to be correctly coded, there was some kind of problem with my input button or welding that the button did exactly the opposite for the what it was programmed, i.e. in my code the button was intended to delay the flashing of the led and it happen to produce the opposite, the led was flashing faster when pushing the button. Here you can see a photo of my button and PCB. Even I welded again the button but it did not work

Next I tested a temperature and moisture sensor (in my case a DHT11 sensor), for that I firstly I installed the DH library in Arduino IDE and used a 3 pin connector using the digital pin D0 for transferring the data from the sensor to my ESP32C3 processor, however it did not work. After researching about it I realized that the problem is that when using the D0 for sensor data it may be an interference causing error in readings in the ESP32 as this pin is commonly used to connect it with the PC. Then I switched the temperature sensor to the 4 pin connector which uses two different pins for data reading and it worked properly. The code I used for temperature monitoring reads as follows:

#include <DHT.h>

// Definición del pin y tipo de sensor
#define DHTPIN D5       // Pin digital al que se conecta el DHT11
#define DHTTYPE DHT11    // Tipo de sensor: DHT11

DHT dht(DHTPIN, DHTTYPE);

void setup() {
  Serial.begin(9600);
  dht.begin();  // Inicialización del sensor
}

void loop() {
  float temperature = dht.readTemperature();
  float humidity = dht.readHumidity();

  if (isnan(temperature) || isnan(humidity)) {
    Serial.println("Error al obtener los datos del sensor DHT11");
    return;
  }

  Serial.print("Temperature = ");
  Serial.print(temperature);
  Serial.println(" °C");

  Serial.print("Humidity = ");
  Serial.print(humidity);
  Serial.println(" %");

  delay(1000);
}

Here you can see the connection of the DHT11 sensor in my PCB

Thirdly, I generated a code for implementing and accelerometer (in my case the ADXL345), which needs a 4 pin connector for working (2 data, power and ground). This sensor also needs preinsallation of a library, in my case the Adafruit_ADXL345 library. The code for making it working reads as follows:

#include <Wire.h>
#include <Adafruit_Sensor.h>
#include <Adafruit_ADXL345_U.h>

Adafruit_ADXL345_Unified accel = Adafruit_ADXL345_Unified(12345);

void displaySensorDetails(void) {
    sensor_t sensor;
    accel.getSensor(&sensor);
    Serial.println("------------------------------------");
    Serial.print("Sensor:       "); Serial.println(sensor.name);
    Serial.print("Driver Ver:   "); Serial.println(sensor.version);
    Serial.print("Unique ID:    "); Serial.println(sensor.sensor_id);
    Serial.print("Max Value:    "); Serial.print(sensor.max_value); Serial.println(" m/s^2");
    Serial.print("Min Value:    "); Serial.print(sensor.min_value); Serial.println(" m/s^2");
    Serial.print("Resolution:   "); Serial.print(sensor.resolution); Serial.println(" m/s^2");
    Serial.println("------------------------------------");
    Serial.println("");
    delay(500);
}

void setup(void) {
    Wire.begin(6, 7);  // SDA = GPIO6, SCL = GPIO7
    Serial.begin(115200);
    while (!Serial);

    Serial.println("Accelerometer Test\n");

    if (!accel.begin(0x53)) {
        Serial.println("❌ Its not detecting the ADXL345... Verify the connections.");
        while (1);
    }

    accel.setRange(ADXL345_RANGE_16_G);
    displaySensorDetails();
}

//without graphic
/*
void loop(void) {
    sensors_event_t event;
    accel.getEvent(&event);

    Serial.print("X: "); Serial.print(event.acceleration.x); Serial.print("  ");
    Serial.print("Y: "); Serial.print(event.acceleration.y); Serial.print("  ");
    Serial.print("Z: "); Serial.print(event.acceleration.z); Serial.print("  "); 
    Serial.println("m/s^2");

    delay(500);
}
*/

// Plot acceleration
void loop(void) {
    sensors_event_t event;
    accel.getEvent(&event);

    Serial.print("X:"); Serial.print(event.acceleration.x); Serial.print(" ");
    Serial.print("Y:"); Serial.print(event.acceleration.y); Serial.print(" ");
    Serial.print("Z:"); Serial.println(event.acceleration.z);  // Usa println solo en el último valor

    delay(100);
}

Here you can see a demonstrative video with X, Y and Z accelerations:

Files for download and replication

Here you can download all the files of the assginment including the Arduino file for the button input Button, temperature and moisture reading THRead and acceleration read Acceleration.

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