Go Down

Topic: Arduino Mega 2560 + DallasTemperature DS18B20 doesn't work. Please help (Read 4978 times) previous topic - next topic


Hi everyone, I have the following setup:

And I have tried every simgle piece of tutorials on the web and no luck the device is never found. I have also read another problems with the Mega and the DS18B20:

But no solution.

The code I use is this:
Code: [Select]
#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into port 2 on the Arduino
#define ONE_WIRE_BUS 12

// Setup a oneWire instance to communicate with any OneWire devices (not just Maxim/Dallas temperature ICs)
OneWire oneWire(ONE_WIRE_BUS);

// Pass our oneWire reference to Dallas Temperature.
DallasTemperature sensors(&oneWire);

int numberOfDevices; // Number of temperature devices found

DeviceAddress tempDeviceAddress; // We'll use this variable to store a found device address

void setup(void)
 // start serial port
 Serial.println("Dallas Temperature IC Control Library Demo");

 // Start up the library
 // Grab a count of devices on the wire
 numberOfDevices = sensors.getDeviceCount();
 // locate devices on the bus
 Serial.print("Locating devices...");
 Serial.print("Found ");
 Serial.print(numberOfDevices, DEC);
 Serial.println(" devices.");

 // report parasite power requirements
 Serial.print("Parasite power is: ");
 if (sensors.isParasitePowerMode()) Serial.println("ON");
 else Serial.println("OFF");
 // Loop through each device, print out address
 for(int i=0;i<numberOfDevices; i++)
   // Search the wire for address
   if(sensors.getAddress(tempDeviceAddress, i))
Serial.print("Found device ");
Serial.print(i, DEC);
Serial.print(" with address: ");

Serial.print("Setting resolution to ");

// set the resolution to 9 bit (Each Dallas/Maxim device is capable of several different resolutions)
sensors.setResolution(tempDeviceAddress, TEMPERATURE_PRECISION);

Serial.print("Resolution actually set to: ");
Serial.print(sensors.getResolution(tempDeviceAddress), DEC);
Serial.print("Found ghost device at ");
Serial.print(i, DEC);
Serial.print(" but could not detect address. Check power and cabling");


// function to print the temperature for a device
void printTemperature(DeviceAddress deviceAddress)
 // method 1 - slower
 //Serial.print("Temp C: ");
 //Serial.print(" Temp F: ");
 //Serial.print(sensors.getTempF(deviceAddress)); // Makes a second call to getTempC and then converts to Fahrenheit

 // method 2 - faster
 float tempC = sensors.getTempC(deviceAddress);
 Serial.print("Temp C: ");
 Serial.print(" Temp F: ");
 Serial.println(DallasTemperature::toFahrenheit(tempC)); // Converts tempC to Fahrenheit

void loop(void)
 // call sensors.requestTemperatures() to issue a global temperature
 // request to all devices on the bus
 Serial.print("Requesting temperatures...");
 sensors.requestTemperatures(); // Send the command to get temperatures
 // Loop through each device, print out temperature data
 for(int i=0;i<numberOfDevices; i++)
   // Search the wire for address
   if(sensors.getAddress(tempDeviceAddress, i))
// Output the device ID
Serial.print("Temperature for device: ");

// It responds almost immediately. Let's print out the data
printTemperature(tempDeviceAddress); // Use a simple function to print out the data
//else ghost device! Check your power requirements and cabling


// function to print a device address
void printAddress(DeviceAddress deviceAddress)
 for (uint8_t i = 0; i < 8; i++)
   if (deviceAddress[i] < 16) Serial.print("0");
   Serial.print(deviceAddress[i], HEX);

Bu I allways get:
[quote]Dallas Temperature IC Control Library Demo
Locating devices...Found 0 devices.
Parasite power is: OFF
Requesting temperatures...DONE
Requesting temperatures...DONE

If anyone could help I be very greatfull.


Hi, I also tried the one wire library, the latest version and it doesn't detect the adress of the Sensor:
Code: [Select]
#include <OneWire.h>

// OneWire DS18S20, DS18B20, DS1822 Temperature Example
// http://www.pjrc.com/teensy/td_libs_OneWire.html
// The DallasTemperature library can do all this work for you!
// http://milesburton.com/Dallas_Temperature_Control_Library

OneWire  ds(6);  // on pin 10

void setup(void) {

void loop(void) {
 byte i;
 byte present = 0;
 byte type_s;
 byte data[12];
 byte addr[8];
 float celsius, fahrenheit;
 if ( !ds.search(addr)) {
   Serial.println("No more addresses.");
 Serial.print("ROM =");
 for( i = 0; i < 8; i++) {
   Serial.write(' ');
   Serial.print(addr[i], HEX);

 if (OneWire::crc8(addr, 7) != addr[7]) {
     Serial.println("CRC is not valid!");

 // the first ROM byte indicates which chip
 switch (addr[0]) {
   case 0x10:
     Serial.println("  Chip = DS18S20");  // or old DS1820
     type_s = 1;
   case 0x28:
     Serial.println("  Chip = DS18B20");
     type_s = 0;
   case 0x22:
     Serial.println("  Chip = DS1822");
     type_s = 0;
     Serial.println("Device is not a DS18x20 family device.");

 ds.write(0x44,1);         // start conversion, with parasite power on at the end
 delay(1000);     // maybe 750ms is enough, maybe not
 // we might do a ds.depower() here, but the reset will take care of it.
 present = ds.reset();
 ds.write(0xBE);         // Read Scratchpad

 Serial.print("  Data = ");
 Serial.print(" ");
 for ( i = 0; i < 9; i++) {           // we need 9 bytes
   data[i] = ds.read();
   Serial.print(data[i], HEX);
   Serial.print(" ");
 Serial.print(" CRC=");
 Serial.print(OneWire::crc8(data, 8), HEX);

 // convert the data to actual temperature

 unsigned int raw = (data[1] << 8) | data[0];
 if (type_s) {
   raw = raw << 3; // 9 bit resolution default
   if (data[7] == 0x10) {
     // count remain gives full 12 bit resolution
     raw = (raw & 0xFFF0) + 12 - data[6];
 } else {
   byte cfg = (data[4] & 0x60);
   if (cfg == 0x00) raw = raw << 3;  // 9 bit resolution, 93.75 ms
   else if (cfg == 0x20) raw = raw << 2; // 10 bit res, 187.5 ms
   else if (cfg == 0x40) raw = raw << 1; // 11 bit res, 375 ms
   // default is 12 bit resolution, 750 ms conversion time
 celsius = (float)raw / 16.0;
 fahrenheit = celsius * 1.8 + 32.0;
 Serial.print("  Temperature = ");
 Serial.print(" Celsius, ");
 Serial.println(" Fahrenheit");

and output:
No more addresses.


Don't use quotes for your code. Use the code tag button labelled '#' immediately to the left of the quote button.



Is the pin number correct?  You are using a shield and the pinnumbers may be incorrect (test a LED on pin 12 will do)

Does the DS18 get the proper voltage? what can you measure on the little board?

Is it getting hot ?   => I found out that temp sensors work "reverse" when connected wrong, they radiate heat iso measuring it  :)

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)


Using a MEGA2560, updated libraries and Arduino IDE 1.0...  here is what I did:

I copied the code from your post (1st one) and installed a DS1820 on a breadboard.  Installed 4.7K to signal pin from 5V. Powered the sensor from 5V (no parasitic). Used the same pins. Uploaded your code unchanged and opened serial monitor.


Code: [Select]
Locating devices...Found 1 devices.
Parasite power is: OFF
Found device 0 with address: 10F0C32500000014
Setting resolution to 9
Resolution actually set to: 9
Requesting temperatures...DONE
Temperature for device: 0
Temp C: 23.76 Temp F: 74.77
Requesting temperatures...DONE
Temperature for device: 0
Temp C: 23.75 Temp F: 74.75

So it's hard to blame the code from my perspective.


Why i cant change resolution ?

Code: [Select]
Locating devices...Found 1 devices.
Parasite power is: OFF
Found device 0 with address: 10475EC402080032
Setting resolution to 9
Resolution actually set to: 12
Requesting temperatures...DONE
Temperature for device: 0
Temp C: 29.81 Temp F: 85.66

i try with two sensors but same


Who would ever know the answer to that? but a guess is that you are not sending the required instruction.

Something like
Code: [Select]
  sensors.setResolution(InThermo, 10);

No instruction means default to 12 bit. You might also get some sensible information from


note that there are two programmes to use, one to sniff the address and the other to use the sensor.

Go Up

Please enter a valid email to subscribe

Confirm your email address

We need to confirm your email address.
To complete the subscription, please click the link in the email we just sent you.

Thank you for subscribing!

via Egeo 16
Torino, 10131