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1-wire device — Parallax Forums

1-wire device

ArchiverArchiver Posts: 46,084
edited 2004-04-12 18:47 in General Discussion
Hi, maybe this is a stupid question but I don't have the answer so
if somebody could educate me it would be apprecaited.

I'm using 6 off DS18S20 temp devices on a one bus wire and a 400 ohm
pull down resistor. Now, my plan is to add one additional 1 wire
devices, a timer device DS 2404, which acc to spec require a pull-up
resistor.

Should I use both or just the pull down

br Lars

Comments

  • ArchiverArchiver Posts: 46,084
    edited 2004-04-12 15:54
    You should be using a pull-UP on a 1-Wire buss (not a pull-down) --
    typically 4.7K, but you may need to stiffen it (say down to 1K) if your
    1-Wire connection is long or has a lot of capacitance.

    -- Jon Williams
    -- Applications Engineer, Parallax
    -- Dallas Office


    Original Message
    From: lars505050 [noparse]/noparse]mailto:[url=http://forums.parallaxinc.com/group/basicstamps/post?postID=c8_7QPhwLWE_QCCjG7Pd2Doxlk1wu9vpmiG4CI-2auzuwc6qaGXlxJ92tg5nQfYmq3QLH76YFKRl3Q8]ls@l...[/url
    Sent: Monday, April 12, 2004 2:47 AM
    To: basicstamps@yahoogroups.com
    Subject: [noparse][[/noparse]basicstamps] 1-wire device


    Hi, maybe this is a stupid question but I don't have the answer so
    if somebody could educate me it would be apprecaited.

    I'm using 6 off DS18S20 temp devices on a one bus wire and a 400 ohm
    pull down resistor. Now, my plan is to add one additional 1 wire
    devices, a timer device DS 2404, which acc to spec require a pull-up
    resistor.

    Should I use both or just the pull down

    br Lars
  • ArchiverArchiver Posts: 46,084
    edited 2004-04-12 18:47
    Thanks, I just realized that I got things mixed up. I ended up with
    a 400 ohm "Pull up" but not more than 16 meters of cable, I guess
    that not an issue as long it works.

    br
    Lars

    --- In basicstamps@yahoogroups.com, "Jon Williams" <jwilliams@p...>
    wrote:
    > You should be using a pull-UP on a 1-Wire buss (not a pull-down) --
    > typically 4.7K, but you may need to stiffen it (say down to 1K) if
    your
    > 1-Wire connection is long or has a lot of capacitance.
    >
    > -- Jon Williams
    > -- Applications Engineer, Parallax
    > -- Dallas Office
    >
    >
    >
    Original Message
    > From: lars505050 [noparse][[/noparse]mailto:ls@l...]
    > Sent: Monday, April 12, 2004 2:47 AM
    > To: basicstamps@yahoogroups.com
    > Subject: [noparse][[/noparse]basicstamps] 1-wire device
    >
    >
    > Hi, maybe this is a stupid question but I don't have the answer so
    > if somebody could educate me it would be apprecaited.
    >
    > I'm using 6 off DS18S20 temp devices on a one bus wire and a 400
    ohm
    > pull down resistor. Now, my plan is to add one additional 1 wire
    > devices, a timer device DS 2404, which acc to spec require a pull-
    up
    > resistor.
    >
    > Should I use both or just the pull down
    >
    > br Lars
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