On Fri, 30 Aug 2002, Micro Eng wrote:

>I've been asked by a neighbor (isn't it great when they find out your an
>engineer)if....
>
>Using his ethernet network, CAT5E runs, that goto everywhere in his house,
>and since there is a unused pairs.....
>
>He wants to monitor the temps in the rooms of the house.  I figured using
>the Dallas one-wire system, and the 2N3906 type temp sensors.

Maybe LM35s+LM317s (one each for each station, maybe LM34s for deg. F)
will work better. I refer to a 4-20mA application using these parts in the
LM35 datasheet.

Plain transistors will rectify some of any ac present and cause
misreadings probably, even if it's twisted pairs, even is proper
decoupling is used.

Peter

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