Am 01.03.2016 um 19:48 schrieb Peter Hollenbeck:
>
> The new temperature sensor is connected with 150 feet of waterproof Cat6.
> When trying to get it working I read that the DS18B20 needs a 4.7K resistor
> connecting +5V to Data.
>
Are you using a dedicated onewire host adapter chip or just a simple
GPIO pin? For the latter you have to connect the pullup to 3.3V, not 5V.
> I lost the resistor that came with the sensor so used 5 1K resistors in
> series instead. (Am at a remote location and must use what I have at hand.)
>
> Q1: Is the cable too long?
>
No.
> Q2: Is 5K okay instead of 4.7K?
>
The pullup may provide up to 4mA. That's the maximum the inidividual
slaves can pulldown. So at 3.3V, it may be as low as 1k.
Make it 1k and connect it to 3.3V.
Kind regards
Jan
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