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Temp Probe (DS18B20) – results without pull-up resistor May 8, 2011

Posted by rik94566 in aquaponic automation, aquaponics, arduino, DIY aquaponics, DS18B20, indoor gardens, indoor growing, Stainless Steel Temp Probe, Temperature Probe.
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Testing Probe without pull-up resistor

Here are the results that are returned from my testing code of probes.  I now know what reading I will get if the 4.7K ohm pull-up resistor is not present or connected wrong or a connection has broken.  I have provided the sketch for download or you can copy it from below.

Lacking 4.7K resistor


Testing Sketch to test construction of temp probes using DS18B20 IC for Stainless Steel probes.
Sketch was created by Miles Burton and changed to display both C and F temperatures using the serial
monitor for display.

created on 11/20/10
by rik kretzinger   version 1.3

#include <OneWire.h>
#include <DallasTemperature.h>

// Data wire is plugged into pin 8 on the Arduino
#define ONE_WIRE_BUS 8

// 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);

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

// Start up the library

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

Serial.print(“Temperature for Device 1 is:              “);
Serial.print(sensors.getTempCByIndex(0)); // Why “byIndex”? You can have more than one IC on the same bus.
// 0 refers to the first IC on the wire.
Serial.println(”  C”);
Serial.print(“FAHRENHEIT CONVERSION                     “);
Serial.print(((sensors.getTempCByIndex(0)*1.8)+32));  // test this line
Serial.println(”  F”);





1. Terry King - May 8, 2011

Thanks for documenting this. One of the biggest help in troubleshooting is knowing specific symptoms or a known failure..

2. Hanna Instruments HI 9812-5N pH, conductivity and TDS in water conditioning Reviews - May 12, 2011

[…] Temp Probe (DS18B20) – results without pull-up resistor … […]

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