Hi all.
I use the esp8266 board in place with 7 pieces of DS18B20 sensors in (parasite mode) and 4.7k resistors (wiring diagram in the attach)
I can not solve the problem of connecting more than 4 sensors to one chain, as soon as I connect the 5 sensor, the temperature is added by 15 Celsius degrees (for example, with 4 sensors it shows 25 Celsius degrees, and when I connect the 5 sensor, it already shows 40 Celsius degrees, and when 7 sensors already shows 85 Celsius degrees), and the sensors all 7 are detected by the system, as well as if you connect them separately then everything works too (sketch below)
#include <OneWire.h>
#include <DallasTemperature.h>
// Data wire is plugged TO GPIO 4
#define ONE_WIRE_BUS 4
// 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);
// Number of temperature devices found
int numberOfDevices;
// We'll use this variable to store a found device address
DeviceAddress tempDeviceAddress;
void setup(){
// start serial port
Serial.begin(9600);
// Start up the library
sensors.begin();
// 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.");
// 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: ");
printAddress(tempDeviceAddress);
Serial.println();
} else {
Serial.print("Found ghost device at ");
Serial.print(i, DEC);
Serial.print(" but could not detect address. Check power and cabling");
}
}
}
void loop(){
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: ");
Serial.println(i,DEC);
// Print the data
float tempC = sensors.getTempC(tempDeviceAddress);
Serial.print("Temp C: ");
Serial.print(tempC);
Serial.print(" Temp F: ");
Serial.println(DallasTemperature::toFahrenheit(tempC)); // Converts tempC to Fahrenheit
}
}
delay(5000);
}
// 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);
}
}