Hey guys, just wondering what the maximum length of a cable can be with one of the DS18B20 temp sensors.
If its not very long how could it be extended (I'm assuming increasing the Vcc from 3.3 to 5v will help). And does all this also apply to having many on the one bus?
The "Notes and further reading" on this page (http://openenergymonitor.org/emon/buildingblocks/DS18B20-temperature-sensing) talks a bit about longer runs with multiple sensors on the one bus, but how far can i go?
Thanks
Re: Max cable length for DS18B20
No answer here ?
Re: Max cable length for DS18B20
How long's a piece of string?
It depends on the network topology and how the devices are driven. See http://pdfserv.maximintegrated.com/en/an/AN148.pdf fro information from the horses mouth.
FWIW I have a number of long strings, the longest is getting on for 40M with about a dozen DS1820s along it. However it is driven by an HA7NET which may have better line drivers than the Arduino.
Re: Max cable length for DS18B20
Did you ever come to a conclusion?
I have just one DS1820 that is probably a good 100ft from the EmonTXv3 and it doesn't seem to be working. I'm going to keep stepping it closer till it does next weekend.
Re: Max cable length for DS18B20
If you read up about the One-wire bus, it's all about reflections and impedance matching. It might help to read up about transmission lines and Time Domain Reflectometry, because that is essentially what happens on the bus, and the effect is of course unwanted in our application. The application note that Billt cites is well worth reading.