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Thread: 1-Wire Modules.

  1. #1

    Default 1-Wire Modules.

    Following on from the 1-Wire thread on the mailling list, I've created a post to allow discussion about purchases of my 1-wire temperature modules.


    More pics here: http://bit.ly/c5Rkxj

    Basically, a PCB mounted sensor, with RJ45 for 1-wire in and out, screw terminals allow connection of an additional external sensor (on a long lead for example).

    Jumper terminal (with the RED jumper) allows selection of powered or parasitic power.

    Price is 9.00 + delivery for a complete kit of parts.
    Assembly is extra.
    If you'd like only part of the kit then let me know which bits.
    Last edited by Otto-Mate; 2nd December 2010 at 01:28 PM. Reason: Price drop

  2. #2
    Automated Home Jr Member SiliconPixel's Avatar
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    Looks good

    what controller(s) do you use for your 1-wire? Oh, and what part is the sensor?

    Paul.

  3. #3

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    Quote Originally Posted by SiliconPixel View Post
    what controller(s) do you use for your 1-wire? Oh, and what part is the sensor?
    I'm using a USB to 1-wire converter then linux with OWFS, the sensor is a DB18B20 which I recommend is used in powered mode rather than parasitic.

  4. #4
    Automated Home Jr Member SiliconPixel's Avatar
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    Thanks Stuart

  5. #5
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    Hi Stuart,

    I've always been interested in these 1-wire sensors but never got a round to doing anything with them. I just have a few questions on the module.
    I assume these can 'daisy chained' along a network (hence the dual RJ45) and use a usb to 1-wire to read them all on my PC?
    Also if I was to use the terminals for an external sensor can it read the external sensor as well as the temp sensor on board or is it just one or the other?
    And finally I assume if the on board temp sensor was left off it will work fine with a sensor installed on the terminals?

    Oh and would you have any problems posting them to Ireland if i got a few off you?

    Cheers
    B

    now to go and actually do some reading up on 1-wires!

  6. #6

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    You are correct the RJ45 connectors simply provide the ability to daisy chain.
    You can use both the screw terminals and the onboard sensor at the same time, you can also only use the external sensor if thats a requirement.

    No problem with posting to Ireland.

  7. #7
    Automated Home Jr Member Simon300's Avatar
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    Question Schottky diode?

    I see that Stuart's PCB has a space for a Schottky diode.

    There's a mention on the digitemp site about putting one at the end of the network. I also found it described in Maxim's AN108 MicroLAN In The Long Run which says:
    "If it is not possible to stretch the timing, a Schottky diode placed across the bus at the far end is suggested to clamp the inductive generated voltage overshoot. Connect the diode across the cable with the cathode on the data line, and the anode on the return. Only one diode is required for each length of MicroLAN with problem inductance."

    How often do people need to add this diode in practice?

  8. #8

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    I've stopped using diodes on the end of branches and have had no problems.
    Best advice I can give is to not use them, if you start seeing problems then remove the last sensor from the chain.
    If removing the last sensor works, try adding the diode to the last sensor and re-instating.

    I think in reality, the use of properly terminated cables really makes a difference, and removes the reflections you see with other sorts of cable termination.

  9. #9
    Automated Home Jr Member Simon300's Avatar
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    Quote Originally Posted by StuartP View Post
    ...I think in reality, the use of properly terminated cables really makes a difference, and removes the reflections you see with other sorts of cable termination.
    Thanks for the reply Stuart. When you say "properly terminated" you mean only use RJ45 (or RJ11 I suppose) connectors and not, say, plastic electrical terminal strips?

  10. #10
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    Hi Stuart, sent you a PM.

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