One-wire Temperature Logging

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I'm looking at this page which shows an easy-enough circuit for a
one-wire temperature sensor tied to a parallel port:
http://www.vss.co.nz/new/gadgets/onewire.htm

A couple of questions:
1. Any comments on this circuit? Does anything jump out as a bad idea or
does it look good?
2. Where would be the best (fastest) place to purchase the DS1820? I
live south-west of Melbourne but anywhere 'round town would do, or a
good, reputable internet dealer.
3. The author of the above webpage suggests that voltage will drop over
long distances and possibly a 'power amp' will do. Last time I used a
power amp was at a rock concert so I'm guessing he means something else.
Suggestions? (I'm hoping to plant about 5 of these around the house at
spare network points so there's a fair bit of total distance)

Cheers!
Rick Measham

Re: One-wire Temperature Logging



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I can't say much about the circuit, but it seems to be based on a Dallas app
note, so it's likely to be kosher.

DS18S20's are pretty easy to get - if you can wait a couple of weeks you
could get free samples from Maxim/Dallas Semiconductor.

You can try running 2 wires and see how you go. If you're having problems,
running a separate 5v line for Vdd might improve things.




Re: One-wire Temperature Logging


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That would feel like stealing .. I'm not planning on ever bulk buying
them and I'd assume that's the premise on which they hand them out :)

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I have 8 available on the empty CAT-5e .. I'm no genius so go slow with
me .. I assume I need to supply the (+) side of 5v to the 'VDD' pin and
the Gnd gets the (-) ? If so, do I need to disconnect the Gnd from the
rest of the circuit? Would I need to make any other changes to the circuit?

Cheers!
Rick Measham

Re: One-wire Temperature Logging


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Is this a long term permanent logging system, or just medium-short
term?
How often do you need to log the temperature and update the results?

The Dallas Thermochron iButtons might be a better solution, and no
wiring needed, fully self contained. Perfect if you only need to take a
few thousand samples at long intervals or get a histogram.

Dave :)


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