This tutorial will cover how to use a Bluetooth thermal printer with an ESP32 and a DHT11 sensor. The Bluetooth thermal printer is used to print temperature and humidity data obtained from the DHT11 sensor. Using the ESP32 as a microcontroller, we can control the thermal printer and DHT11 sensor and transmit data via Bluetooth.
Components Used
Below is a list of components used in this project along with purchase links at the Golite Store:
- ESP32 Development Board
- Printer Thermal Bluetooth
- Sensor DHT11
- Push Button
System Scheme
Fritzing Scheme
Pinout Configuration
- ESP32 -> Printer Thermal Bluetooth
- VIN -> VCC
- GND -> GND
- TX2 -> RX
- RX2 -> TX
- ESP32 -> Sensor DHT11
- VIN -> VCC
- GND -> GND
- D4 -> Data
- ESP32 -> Push Button
- GND -> S1
- D18 -> S2
A brief explanation of the system schematic: The ESP32 is connected to a Bluetooth thermal printer via a UART serial connection, and also to a DHT11 sensor to read temperature and humidity data.
Program Arduino/ESP32
#include "Adafruit_Thermal.h"
#include "BluetoothSerial.h"
#include "DHT.h"
#define button 18
#define DHTPIN 4
#define DHTTYPE DHT11
DHT dht(DHTPIN, DHTTYPE);
BluetoothSerial SerialBT;
Adafruit_Thermal printer(&SerialBT);
uint8_t address[6] = {0x66, 0x32, 0x75, 0x31, 0x23, 0x41};
String name = "RPP02N";
char *pin = "0000";
String data;
void setup() {
Serial.begin(115200);
dht.begin();
pinMode(button, INPUT_PULLUP);
pinMode(2, OUTPUT);
SerialBT.setPin(pin);
SerialBT.begin("ESP32test", true);
Serial.println("The device started in master mode, make sure remote BT device is on!");
if (SerialBT.connect(address)) {
Serial.println("Connected Successfully!");
} else {
while (!SerialBT.connected(10000)) {
Serial.println("Failed to connect. Make sure remote device is available and in range, then restart app.");
digitalWrite(2, 1);
delay(500);
digitalWrite(2, 0);
delay(500);
}
}
if (SerialBT.disconnect()) {
Serial.println("Disconnected Successfully!");
}
SerialBT.connect();
printer.begin();
printer.feed(1);
printer.setDefault();
digitalWrite(2, 1);
}
void loop() {
float h = dht.readHumidity();
float t = dht.readTemperature();
float f = dht.readTemperature(true);
if (isnan(h) || isnan(t) || isnan(f)) {
Serial.println(F("Failed to read from DHT sensor!"));
return;
}
float hif = dht.computeHeatIndex(f, h);
float hic = dht.computeHeatIndex(t, h, false);
if (!digitalRead(button)) {
Serial.println("PRINT START");
// Print the data to the thermal printer
printer.justify('C');
printer.println("IDRUS PROJECT x GoLite Store");
printer.println("-----------------");
printer.print("Temperature: ");
printer.print(t);
printer.println(" C");
printer.print("Humidity: ");
printer.print(h);
printer.println("%");
printer.print("Heat Index: ");
printer.print(hic);
printer.println(" C");
printer.feed(2);
}
delay(100); // Adjust delay as needed
}