[aklug] Re: Making a temperature sensor

You should look into the maxim-ic DS18S20 "1-wire" digital devices. They
are about the same size as the analog parts, and with linux you can get
up and running pretty fast. They have three leads, 5V, return, and data.
You can get a 1-wire bus master for USB or RS232, and daisy-chain dozens
of devices quite a distance away. Each has it's own unique address and
the software goes out and finds them all. I'm running owfs and owhttpd
to talk to the devices with a USB bus master. I use rrdtool to grab the
temperatures from the owfs (one-wire file system) periodically and make
graphs I can check out online. You can see them at 99645 dot com port
3002 . For my only outside sensor I heat shrinked the whole thing and
left the top of the device exposed so it responds quickly. If you want
to pot the device, 2-part epoxy and empty shell casings should work. I
think they'll fit in a .22. The only downside I have found with these is
that they seem to bottom out at about -32F.

Bob at Estiminc wrote:
> I'm interested in making up my own temperature=20
> sensors using National Semiconductor LM34 IC's.=20
> It looks like a transistor, a small can with=20
> three wires coming out of it. Connect one wire to=20
> ground, the 2nd to 5VDC and the third puts out a linear +10.0 mV/=B0F.
>
> spec sheet: http://www.national.com/mpf/LM/LM34.html#Overview
>
> My idea is to solder up the cable connections,=20
> shrink some heat tube around each leg, slip it=20
> all into a short length of 1/4" copper tube and=20
> seal it all up with some sort of potting compound.
>
> I have a couple of questions. First of all, does=20
> this sound like a good approach? Any better ideas? Hints? Tips? Tricks?
>
> Secondly, I'm looking for recommendations or=20
> thoughts on a good potting compound -- something=20
> thermally conductive but electrically insulating.=20
> Is RTV silicon a suitable candidate?
>
> Bob Crosby
>
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Received on Sat Nov 21 16:15:14 2009