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Author Topic: multiple ds18b20 sensors = not working  (Read 718 times)
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I am hoping someone can assist me with an odd ds18b20 issue  smiley-mr-green

I have 3 ds18b20 sensors that I bench tested by manually wiring them all 3 to power then the signal pin of each went to a breadboard that had a 4.7k resistor between them and a pin on my arduino.  It worked great, all 3 sensors registered temps at the same time.

After that I wired two of the sensors up on the end of the same cable (sharing power/ground/signal) and connected it and confirmed it worked as expected (two temps shown).  When that was done I wired up the final sensor and confirmed it also worked as expected.

Unfortunately what is *not* working is having both cables (all 3 sensors) connected at the same time.  Either one works by itself but as soon as I plug the second signal connection in the arduino acts like it cannot see any sensors.

FWIW I am using the onewire example code and an arduino mega connected to pin 53.

Any ideas?
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Grand Blanc, MI, USA
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The 4.7K resistor does not go "between" the DS18B20s and the Arduino pin, it's a pullup resistor from the data pin to Vcc. Any chance of posting a schematic?
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Dropped down to a 1k resistor and it is working now  smiley
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This is the wiring schematic I used:  http://bildr.org/2011/07/ds18b20-arduino/

Cheers
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