user-1: I have had a DS18B20-PAR for some time and have often used it without a problem until now. Yesterday it just suddenly stopped working. I was trying to use it along with two i2C sensors at the time. I don't really know of anything which could have fried it, though.
Edit: It is turning out much more complicated than I thought. I can't ever get it to work on pin 10. The sensor sometimes works on other pins (3, 9 and 11), but it often does not. I can still use pin 10 to blink and fade an LED, and receive input from a button, but it never picks up my DS18B20-PAR. What is happening here?
My setup:
I have just one DS18B20-PAR connected to my Arduino Uno look-alike as shown in the following image:

Please note that on the DS18B20-PAR the third pin is internally not connected.
The code:
My Arduino is running this code (a OneWire example sketch which has always worked before):
#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(10);  // on pin 10 (a 4.7K resistor is necessary)

void setup(void) {
  Serial.begin(9600);
}

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.println();
    ds.reset_search();
    delay(250);
    return;
  }
  
  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!");
      return;
  }
  Serial.println();
 
  // the first ROM byte indicates which chip
  switch (addr[0]) {
    case 0x10:
      Serial.println("  Chip = DS18S20");  // or old DS1820
      type_s = 1;
      break;
    case 0x28:
      Serial.println("  Chip = DS18B20");
      type_s = 0;
      break;
    case 0x22:
      Serial.println("  Chip = DS1822");
      type_s = 0;
      break;
    default:
      Serial.println("Device is not a DS18x20 family device.");
      return;
  } 

  ds.reset();
  ds.select(addr);
  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.select(addr);    
  ds.write(0xBE);         // Read Scratchpad

  Serial.print("  Data = ");
  Serial.print(present, HEX);
  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);
  Serial.println();

  // Convert the data to actual temperature
  // because the result is a 16 bit signed integer, it should
  // be stored to an "int16_t" type, which is always 16 bits
  // even when compiled on a 32 bit processor.
  int16_t 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);
    // at lower res, the low bits are undefined, so let's zero them
    if (cfg == 0x00) raw = raw & ~7;  // 9 bit resolution, 93.75 ms
    else if (cfg == 0x20) raw = raw & ~3; // 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.print(" Celsius, ");
  Serial.print(fahrenheit);
  Serial.println(" Fahrenheit");
}

On the serial monitor is just prints "No more addresses." every 250 milliseconds.

user27653: If the setup worked fine and then stopped, you must examine what changed. If your code is unchanged then it could be your sensor or your Arduino. 
You can try putting the sensor on a different input pin and update the code accordingly. 
You can try the sensor on a different Arduino or a new sensor if the same type on your Arduino. 
These are the first steps to troubleshooting. 

-1: <p>I have had a DS18B20-PAR for some time and have often used it without a problem until now. Yesterday it just suddenly stopped working. I was trying to use it along with two i2C sensors at the time. I don't really know of anything which could have fried it, though.</p>
<p><strong>Edit</strong>: It is turning out much more complicated than I thought. I can't ever get it to work on pin 10. The sensor sometimes works on other pins (3, 9 and 11), but it often does not. I can still use pin 10 to blink and fade an LED, and receive input from a button, but it never picks up my DS18B20-PAR. What is happening here?</p>
<h1>My setup:</h1>
<p>I have just one DS18B20-PAR connected to my Arduino Uno look-alike as shown in the following image:</p>
<p><a href="https://i.stack.imgur.com/M98lQ.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/M98lQ.jpg" alt="enter image description here" /></a></p>
<p>Please note that on the DS18B20-PAR the third pin is internally not connected.</p>
<h1>The code:</h1>
<p>My Arduino is running this code (a OneWire example sketch which has always worked before):</p>
<pre><code>#include &lt;OneWire.h&gt;

// 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(10);  // on pin 10 (a 4.7K resistor is necessary)

void setup(void) {
  Serial.begin(9600);
}

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(&quot;No more addresses.&quot;);
    Serial.println();
    ds.reset_search();
    delay(250);
    return;
  }
  
  Serial.print(&quot;ROM =&quot;);
  for( i = 0; i &lt; 8; i++) {
    Serial.write(' ');
    Serial.print(addr[i], HEX);
  }

  if (OneWire::crc8(addr, 7) != addr[7]) {
      Serial.println(&quot;CRC is not valid!&quot;);
      return;
  }
  Serial.println();
 
  // the first ROM byte indicates which chip
  switch (addr[0]) {
    case 0x10:
      Serial.println(&quot;  Chip = DS18S20&quot;);  // or old DS1820
      type_s = 1;
      break;
    case 0x28:
      Serial.println(&quot;  Chip = DS18B20&quot;);
      type_s = 0;
      break;
    case 0x22:
      Serial.println(&quot;  Chip = DS1822&quot;);
      type_s = 0;
      break;
    default:
      Serial.println(&quot;Device is not a DS18x20 family device.&quot;);
      return;
  } 

  ds.reset();
  ds.select(addr);
  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.select(addr);    
  ds.write(0xBE);         // Read Scratchpad

  Serial.print(&quot;  Data = &quot;);
  Serial.print(present, HEX);
  Serial.print(&quot; &quot;);
  for ( i = 0; i &lt; 9; i++) {           // we need 9 bytes
    data[i] = ds.read();
    Serial.print(data[i], HEX);
    Serial.print(&quot; &quot;);
  }
  Serial.print(&quot; CRC=&quot;);
  Serial.print(OneWire::crc8(data, 8), HEX);
  Serial.println();

  // Convert the data to actual temperature
  // because the result is a 16 bit signed integer, it should
  // be stored to an &quot;int16_t&quot; type, which is always 16 bits
  // even when compiled on a 32 bit processor.
  int16_t raw = (data[1] &lt;&lt; 8) | data[0];
  if (type_s) {
    raw = raw &lt;&lt; 3; // 9 bit resolution default
    if (data[7] == 0x10) {
      // &quot;count remain&quot; gives full 12 bit resolution
      raw = (raw &amp; 0xFFF0) + 12 - data[6];
    }
  } else {
    byte cfg = (data[4] &amp; 0x60);
    // at lower res, the low bits are undefined, so let's zero them
    if (cfg == 0x00) raw = raw &amp; ~7;  // 9 bit resolution, 93.75 ms
    else if (cfg == 0x20) raw = raw &amp; ~3; // 10 bit res, 187.5 ms
    else if (cfg == 0x40) raw = raw &amp; ~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(&quot;  Temperature = &quot;);
  Serial.print(celsius);
  Serial.print(&quot; Celsius, &quot;);
  Serial.print(fahrenheit);
  Serial.println(&quot; Fahrenheit&quot;);
}
</code></pre>
<p>On the serial monitor is just prints &quot;No more addresses.&quot; every 250 milliseconds.</p>
 27653: <p>If the setup worked fine and then stopped, you must examine what changed. If your code is unchanged then it could be your sensor or your Arduino. </p>

<p>You can try putting the sensor on a different input pin and update the code accordingly. </p>

<p>You can try the sensor on a different Arduino or a new sensor if the same type on your Arduino. </p>

<p>These are the first steps to troubleshooting. </p>
