I have a utility sketch that you can use to get the internal serial number (Device Address) on DS18B20's that you have. Then you can use those addresses in the code for multiple temperature sensors on one wire. This is important so you can know "which sensor is which" in a bus environment. You can see that info here: https://arduinoinfo.mywikis.net/wiki/Brick-Temperature-DS18B20
G'Day Gang,
I seem to be having trouble finding the addresses of 2 DS18B20 temp probes. I have them set up on a bread board with a 4.7k pull up
resister.
I am using this sketch.
/* YourDuino Example: Find Address of a DS18B20 Temperature Sensor
Cut and paste the address to a text file for later use.
V1.1 01/17/2013
Questions: terry@yourduino.com
Connections:
DS18B20 Pinout (Left to Right, pins down, flat side toward you)
- Left = Ground
- Center = Signal (Pin 2): (with 3.3K to 4.7K resistor to +5 or 3.3 )
- Right = +5 or +3.3 V
This sketch looks for 1-wire devices and prints their addresses (serial number)
to the Serial Monitor in a format that is useful in Arduino sketches.
Based on example at:
http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html
*/
/*-----( Import needed libraries )-----*/
#include <OneWire.h>
/*-----( Declare Constants and Pin Numbers )-----*/
#define SENSOR_PIN 2 // Any pin 2 to 12 (not 13) and A0 to A5
/*-----( Declare objects )-----*/
OneWire ourBus(SENSOR_PIN); // Create a 1-wire object
void setup() /****** SETUP: RUNS ONCE ******/
{
Serial.begin(9600);
discoverOneWireDevices(); // Everything happens here!
}//--(end setup )---
void loop() /****** LOOP: RUNS CONSTANTLY ******/
{
// Nothing happening here
}
/*-----( Declare User-written Functions )-----*/
void discoverOneWireDevices(void) {
byte i;
byte present = 0;
byte data[12];
byte addr[8];
Serial.print("Looking for 1-Wire devices...\n\r");// "\n\r" is NewLine
while(ourBus.search(addr)) {
Serial.print("\n\r\n\rFound \'1-Wire\' device with address:\n\r");
for( i = 0; i < 8; i++) {
Serial.print("0x");
if (addr[i] < 16) {
Serial.print('0');
}
Serial.print(addr[i], HEX);
if (i < 7) {
Serial.print(", ");
}
}
if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.print("CRC is not valid!\n\r");
return;
}
}
Serial.println();
Serial.print("Done");
ourBus.reset_search();
return;
}
//*********( THE END )***********
The sketch compiles ok and uploads fine.
When I open the serial monitor I get
"Looking for 1-Wire devices...
Done"
and no device addresses.
I have checked and rechecked pin numbers and connections but still no joy.
Any ideas pls
Another solution is to repeatedly click the 'reset' button on your Arduino. You normally have to click it at least once for the program to work.
Hello,
I had the same problem recently, using the Hacktronics 1-Wire Address Finder. It ended up that the resistor was not placed in the right spot, connecting power and signal. I used a 10k ohm resistor in place of the 4.7k, as that was all I had at the time. It seems to work alright now, reading the same temperature as my analog manual thermometers. I located the address perfectly but when I loaded the multiple-sensor code, with the correct addresses, it failed. I used the bildr guide which can only use 1 temperature sensor. However, a member posted a code with capability for multiple sensors in the code, which solved my problems.
Following is the 1-Wire Address Finder
// This sketch looks for 1-wire devices and
// prints their addresses (serial number) to
// the UART, in a format that is useful in Arduino sketches
// Tutorial:
// http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html
#include <OneWire.h>
OneWire ds(3); // Connect your 1-wire device to pin 3
void setup(void) {
Serial.begin(9600);
discoverOneWireDevices();
}
void discoverOneWireDevices(void) {
byte i;
byte present = 0;
byte data[12];
byte addr[8];
Serial.print("Looking for 1-Wire devices...\n\r");
while(ds.search(addr)) {
Serial.print("\n\rFound \'1-Wire\' device with address:\n\r");
for( i = 0; i < 8; i++) {
Serial.print("0x");
if (addr[i] < 16) {
Serial.print('0');
}
Serial.print(addr[i], HEX);
if (i < 7) {
Serial.print(", ");
}
}
if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.print("CRC is not valid!\n");
return;
}
}
Serial.print("\n\r\n\rThat's it.\r\n");
ds.reset_search();
return;
}
void loop(void) {
// nothing to see here
}
And here is the 'comment' code I am using currently
#include <OneWire.h>
int DS18S20_Pin = 4; //DS18S20 Signal pin on digital 4
//Temperature chip i/o
OneWire ds(DS18S20_Pin); // on digital pin 4
void setup(void) {
Serial.begin(9600);
}
void loop(void) {
float temperature = getTemp();
Serial.print ("The inside temperature in Degrees Celsius is:") ;
Serial.println(temperature);
delay(1000); //just here to slow down the output so it is easier to read
}
float getTemp(){
//returns the temperature from one DS18S20 in DEG Celsius
byte data[12];
byte addr[8];
if ( !ds.search(addr)) {
//no more sensors on chain, reset search
ds.reset_search();
return -1000;
}
if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.println("CRC is not valid!");
return -1000;
}
if ( addr[0] != 0x10 && addr[0] != 0x28) {
Serial.print("Device is not recognized");
return -1000;
}
ds.reset();
ds.select(addr);
ds.write(0x44,1); // start conversion, with parasite power on at the end
byte present = ds.reset();
ds.select(addr);
ds.write(0xBE); // Read Scratchpad
for (int i = 0; i < 9; i++) { // we need 9 bytes
data[i] = ds.read();
}
ds.reset_search();
byte MSB = data[1];
byte LSB = data[0];
float tempRead = ((MSB << 8) | LSB); //using two's compliment
float TemperatureSum = tempRead / 16;
return TemperatureSum;
}
marcusdeans:
I used a 10k ohm resistor in place of the 4.7k, but when I loaded the multiple-sensor code, with the correct addresses, it failed.
Quite likely due to the wrong resistor. The pullup isn't critical, hence 10k with one DS18B20 is OK, but having twice the recommended resistance working with two is probably stretching the friendship.
Hi All, please how can I read the MAC address of the DHT22 sensor connected to the arduino uno board?
I want to connect multiple DHT22 and will need to take readings of each at thesame time and I need the MAC address of each sensor to do this. Thank you.
I've just got two of these sensors and I'm having trouble finding their unique address.
I've been using this code as found on hacktronics...
// This sketch looks for 1-wire devices and
// prints their addresses (serial number) to
// the UART, in a format that is useful in Arduino sketches
// Tutorial:
// http://www.hacktronics.com/Tutorials/arduino-1-wire-address-finder.html
#include <OneWire.h>
OneWire ds(3); // Connect your 1-wire device to pin 3
void setup(void) {
Serial.begin(9600);
discoverOneWireDevices();
}
void discoverOneWireDevices(void) {
byte i;
byte present = 0;
byte data[12];
byte addr[8];
Serial.print("Looking for 1-Wire devices...");
while(ds.search(addr)) {
Serial.print("\n\rFound \'1-Wire\' device with address:\n\r");
for( i = 0; i < 8; i++) {
Serial.print("0x");
if (addr[i] < 16) {
Serial.print('0');
}
Serial.print(addr[i], HEX);
if (i < 7) {
Serial.print(", ");
}
}
if ( OneWire::crc8( addr, 7) != addr[7]) {
Serial.print("CRC is not valid!\n");
return;
}
}
Serial.print("\n\r\n\rThat's it.\r\n");
ds.reset_search();
return;
}
void loop(void) {
// nothing to see here
}
However the response is get is this:
?"Ásip.
ÁHookingfor!-Wire`eviCes..."
If I unplug it and run the sketch then I get a coherent response:
Thanks for quick response. Yeah you're right . I was going off the micro process pin 3 (digital pin 1). Hence my error. Got the addresses for my sensors now!
I need to write a function that can read 3 sensors (ds18b20) without knowing their address... i.e. we just know what socket (pins) they are to be plugged but I cant rely on the device address since they can be changed...
I tried looking up how the i2c bus assigns the index number so I could just refer to index number but didnt find any info...
anyway, I thought I could turn ON/OFF the power pin of the sensor thus only that sensor will report in to the bus... Dont know if Im screwing up something so thought I would ask.. Maybe a better way thus avoiding the use of so many resources?
Here is how the function will be called out, (all data wires to the same bus)
If I understand correctly, just use onewire and define the ds pins like this:
#include <OneWire.h>
OneWire ds_1(10); //sensor 1 on pin 10
OneWire ds_2(11); //sensor 2 on pin 11
OneWire ds_3(12); //sensor 3 on pin 12
//Then search every pin for its address and request temps
#include <OneWire.h>
OneWire ds_1(10); //sensor 1 on pin 10
OneWire ds_2(11); //sensor 2 on pin 11
OneWire ds_3(12); //sensor 3 on pin 12
//Then search every pin for its address and request temps
DallasTemperature sensor_1(&ds_1);
DallasTemperature sensor_2(&ds_2);
DallasTemperature sensor_3(&ds_3);
........
sensor_1.begin();
sensor_1.requestTemperatures();
temp_1 = sensor_1.getTempCByIndex(0);
(3 times) you get the idea
I have 3 of this working thanks to your tutorial. Is there a humidity sensor that will work on the same pin as these temp sensors or does it have to go on its own pin.
Thanks I have ordered a dht11. I dont really want it for temp only humidity. Can I assume that both the 11 and the 22 will go on the same buss as the ds18b20
. I was going off the micro process pin 3 (digital pin 1). Hence my error. Got the addresses for my sensors now! 
