One-wire Temperature Logging

Aug 08, 2006 3 Replies
R

I'm looking at this page which shows an easy-enough circuit for a one-wire temperature sensor tied to a parallel port:

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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


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P

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.

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R

...

Poxy wrote:

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 :)

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

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D

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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