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Thread: Max cable Length to 1-wire devices

  1. #1

    Default Max cable Length to 1-wire devices

    I am building a project that will measure the temperature in the different levels of my home and report back to a picaxe. Is there a maximum length of cable for 1-wire devices? Is there any special circuitry that must be used to protect the chips?

  2. #2
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    Easy to find out by experimentation. Let us know.

  3. #3
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    I recall reading the spec in one of the docs. Possibly the DS18B20 temperature. It gave me confidence to have an 12 metre run within my house for measuring roofspace temperatures (solar heating project).

  4. #4
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    I recall reading somewhere that someone had DS18B20's working over 100m of Cat5 cable but it's really a case of try it and see. Please do let us know how far you get it to work at.

  5. #5
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    Hi Burnie,
    I have used several meters with no problems. Would use 5 Volts to power them (not parasite power). The voltage drop is only quite small because of the very low currents but use cable of twisted pair and/or shielded, eg; Cat5, you must avoid any induction/noise from high voltage sources running nearby. I used 100mA quick blow glass in-line fuses to protect the circuit in case of a short occuring due to any damage to cable run or sensor. You could experiment by connecting up the sensor with clips to the end of a long length of cable coiled in the same room. There is more info if you go from this page to home/links/Peter Anderson/ scroll to sample routines/a three point monitor using DS18B20. He quotes success using 200 ft of cable. Anyway, as the others say- let us know how you go!

  6. #6
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    I vaguely remember a project, either EA or
    Silicon Chip years back, first generation
    of chips, guy in Melbourne. I think the
    figures were something like 600 meters.

    I'll have a look, I had some notes he sent
    about the project. Don't quote me yet !

  7. #7
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    Try this -

    <A href='http://www.maxim-ic.com/appnotes.cfm/appnote_number/148' Target=_Blank>External Web Link</a>

  8. #8

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    Thanks for all the quick replies, I will definately post my results. I have 500Ft box of Cat 5 that I plan to experiment with although the max distance of my runs will most likely be 150ft.

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