Interfacing Multiple DS18B20 Temperature Sensors to Microcontroller:
In this project we will learn about Interfacing Multiple DS18B20 Temperature Sensors to Microcontroller ATmega328. Simply we will connect Multiple DS18B20 Temperature Sensors to Microcontroller pin and display the temperature values of all the sensors in degree celsius or Fahrenheit. Only one digital pin of Microcontroller ATmega328 is required to connect several temperature sensor. We can connect maximum of 1024 sensors using I2C Protocol. But here i have shown connecting 3 DS18B20 Temperature Sensors to Microcontroller ATmega328.
The DS18B20 temperature sensor is a 1-wire digital temperature sensor. This comes with sealed package lets precisely measure temperatures in wet environments with a simple 1-Wire interface. It communicates on common bus. It means it can connect several devices and read their values using just one digital pin of the Microcontroller.
DS18B20 Waterproof Digital Temperature Sensor:
This is a pre-wired and waterproofed version of the DS18B20 sensor. Handy for when you need to measure something far away, or in wet conditions. The Sensor can measure the temperature between -55 to 125°C (-67°F to +257°F). The cable is jacketed in PVC.
Because it is digital, there is no any signal degradation even over long distances. These 1-wire digital temperature sensors are fairly precise, i.e ±0.5°C over much of the range. It can give up to 12 bits of precision from the onboard digital-to-analog converter. They work great with any microcontroller using a single digital pin.
The only downside is they use the Dallas 1-Wire protocol, which is somewhat complex and requires a bunch of code to parse out the communication. We toss in a 4.7k resistor, which is required as a pullup from the DATA to the VCC line when using the sensor.
Components Required:
- ATmega328 Microcontroller
- Multiple DS18B20 Waterproof Temperature Sensor
- 16*2 LCD Display
- 4.7K, 1M & 100 ohm Resistors
- 22pF, 10uF & 22pF Capacitors
- 16 MHz Crystal Oscillator
- 5 Volt Power Supply or Battery
Circuit Diagram & Connections:
Hardware & Design:
By connecting all the sensors to one digital pin of Microcontroller ATmega328 we have simply designed Digital Thermometer for measuring multiple temperatures. So the below picture tells how we have Interfaced Multiple DS18B20 Temperature Sensors to Microcontroller ATmega328 and how the temperature is being displayed.
Source Code/Program:
We have used Arduino Language to write the code and upload it to the microcontroller. Take a fresh ATmega328 and insert it into Arduino UNO Board. First, upload the bootloader. Then simply compile the below code and upload it to the microcontroller. Now you can remove the microcontroller and insert it into PCB.
For interfacing Multiple DS18B20 Temperature Sensors to ATmega328 microcontroller you need two different library
1. Download 1 Wire Library
2. Download Dallas Temperature Library
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#include <LiquidCrystal.h> LiquidCrystal lcd(11, 12, 5, 4, 3, 2); #include <OneWire.h> #include <DallasTemperature.h> #define ONE_WIRE_BUS 9 // Data wire is plugged into port 9 on the Arduino #define precision 12 // OneWire precision Dallas Sensor int sen_number = 0; // Counter of Dallas sensors OneWire oneWire(ONE_WIRE_BUS); DallasTemperature sensors(&oneWire); // Pass our oneWire reference to Dallas Temperature. DeviceAddress T1, T2, T3, T4, T5, T6, T7, T8; // arrays to hold device addresses void setup(void) { lcd.begin(16,2); Serial.begin(9600); //Start serial port Serial.println("Dallas Temperature IC Control Library"); // Start up the library sensors.begin(); // locate devices on the bus Serial.print("Found: "); Serial.print(sensors.getDeviceCount(), DEC); Serial.println(" Devices."); // report parasite power requirements Serial.print("Parasite power is: "); if (sensors.isParasitePowerMode()) Serial.println("ON"); else Serial.println("OFF"); // Search for devices on the bus and assign based on an index. if (!sensors.getAddress(T1, 0)) Serial.println("Not Found Sensor 1"); if (!sensors.getAddress(T2, 1)) Serial.println("Not Found Sensor 2"); if (!sensors.getAddress(T3, 2)) Serial.println("Not Found Sensor 3"); if (!sensors.getAddress(T4, 3)) Serial.println("Not Found Sensor 4"); if (!sensors.getAddress(T5, 4)) Serial.println("Not Found Sensor 5"); if (!sensors.getAddress(T6, 5)) Serial.println("Not Found Sensor 6"); if (!sensors.getAddress(T7, 6)) Serial.println("Not Found Sensor 7"); if (!sensors.getAddress(T8, 7)) Serial.println("Not Found Sensor 8"); // show the addresses we found on the bus for (int k =0; k < sensors.getDeviceCount(); k++) { Serial.print("Sensor "); Serial.print(k+1); Serial.print(" Address: "); if (k == 0) { printAddress(T1); Serial.println(); } else if (k == 1) { printAddress(T2); Serial.println(); } else if (k == 2) { printAddress(T3); Serial.println(); } else if (k == 3) { printAddress(T4); Serial.println(); } else if (k == 4) { printAddress(T5); Serial.println(); } else if (k == 5) { printAddress(T6); Serial.println(); } else if (k == 6) { printAddress(T7); Serial.println(); } else if (k == 7) { printAddress(T8); Serial.println(); } } // set the resolution to 12 bit per device sensors.setResolution(T1, precision); sensors.setResolution(T2, precision); sensors.setResolution(T3, precision); sensors.setResolution(T4, precision); sensors.setResolution(T5, precision); sensors.setResolution(T6, precision); sensors.setResolution(T7, precision); sensors.setResolution(T8, precision); for (int k =0; k < sensors.getDeviceCount(); k++) { Serial.print("Sensor "); Serial.print(k+1); Serial.print(" Resolution: "); if (k == 0) { Serial.print(sensors.getResolution(T1), DEC); Serial.println(); } else if (k == 1) { Serial.print(sensors.getResolution(T2), DEC); Serial.println(); } else if (k == 2) { Serial.print(sensors.getResolution(T3), DEC); Serial.println(); } else if (k == 3) { Serial.print(sensors.getResolution(T4), DEC); Serial.println(); } else if (k == 4) { Serial.print(sensors.getResolution(T5), DEC); Serial.println(); } else if (k == 5) { Serial.print(sensors.getResolution(T6), DEC); Serial.println(); } else if (k == 6) { Serial.print(sensors.getResolution(T7), DEC); Serial.println(); } else if (k == 7) { Serial.print(sensors.getResolution(T8), DEC); Serial.println(); } } } // function to print a device address void printAddress(DeviceAddress deviceAddress) { for (uint8_t i = 0; i < 8; i++) { // zero pad the address if necessary if (deviceAddress[i] < 16) Serial.print("0"); Serial.print(deviceAddress[i], HEX); } } // function to print the temperature for a device void printTemperature(DeviceAddress deviceAddress) { float tempC = sensors.getTempC(deviceAddress); Serial.print("Temp : "); Serial.print(tempC); Serial.print(" Celcius degres "); // Serial.print(" Temp F: "); // Serial.print(DallasTemperature::toFahrenheit(tempC)); } // function to print a device's resolution void printResolution(DeviceAddress deviceAddress) { } void printData(DeviceAddress deviceAddress) { Serial.print("Device Address: "); printAddress(deviceAddress); Serial.print(" "); printTemperature(deviceAddress); Serial.println(); } void loop(void) { // call sensors.requestTemperatures() to issue a global temperature request to all devices on the bus Serial.print("Reading DATA..."); sensors.requestTemperatures(); Serial.println("DONE"); // print the device information for (int k =0; k < sensors.getDeviceCount(); k++) { Serial.print("Sensor "); Serial.print(k+1); Serial.print(" "); if (k == 0) { printData(T1); } else if (k == 1) { printData(T2); } else if (k == 2) { printData(T3); } else if (k == 3) { printData(T4); } else if (k == 4) { printData(T5); } else if (k == 5) { printData(T6); } else if (k == 6) { printData(T7); } else if (k == 7) { printData(T8); } } if (sen_number == sensors.getDeviceCount()) { sen_number = 0; // reset counter // lcd.clear(); // clear screen on LCD } lcd.setCursor(0,0); lcd.print("Sensor Number "); lcd.print(sen_number+1); lcd.setCursor(0,1); lcd.print(" Temp: "); if (sen_number == 0) { lcd.print(sensors.getTempC(T1)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 1) { lcd.print(sensors.getTempC(T2)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 2) { lcd.print(sensors.getTempC(T3)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 3) { lcd.print(sensors.getTempC(T4)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 4) { lcd.print(sensors.getTempC(T5)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 5) { lcd.print(sensors.getTempC(T6)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 6) { lcd.print(sensors.getTempC(T7)); lcd.write((char)223); lcd.print("C "); } else if (sen_number == 7) { lcd.print(sensors.getTempC(T8)); lcd.write((char)223); lcd.print("C "); } Serial.print("Sensor Number="); Serial.println(sen_number); delay(2000); sen_number++ ; } |
Working of Multiple DS18B20 Temperature Sensors with Microcontroller:
The DS18B20 provides 9 to 12-bit (configurable) temperature readings which indicate the temperature of the device. It communicates over a 1-Wire bus that by definition requires only one data line (and ground) for communication with a central microprocessor. In addition, it can derive power directly from the data line (“parasite power”), eliminating the need for an external power supply.
The core functionality of the DS18B20 is its direct-to-digital temperature sensor. The resolution of the temperature sensor is user-configurable to 9, 10, 11, or 12 bits, corresponding to increments of 0.5°C, 0.25°C, 0.125°C, and 0.0625°C, respectively. The default resolution at power-up is 12-bit.
Each and every DS18B20 has particular device address in HEX format like { 0x28, 0x1D, 0x39, 0x31, 0x2, 0x0, 0x0, 0xF0 }. So the program is designed on the basis of reading temperature from a particular device address. So first the microcontroller scans the number of sensors. Let us assume 3 sensors are connected here. So it will just display values of 3 different readings. If more sensors are connected, the reading will switch to multiple values. The value of temperature read by each sensor is displayed after an interval of 2 seconds as Sensor Number 1 Temperature, Sensor Number 2 Temperature, and up to the value of a number of sensors connected.
To learn more about the code you can go through the video below. Or simply read the code as I have commented on each and everything about each line in code.
Video Tutorial & Explanation:
