[aprssig] House Temperature Probing

Scott Miller scott at opentrac.org
Sat Dec 9 13:50:12 CST 2006

It self-heats only if you're putting a significant load on the regulator.
You can also remote the sensor pretty easily.  Or you can load the Dallas
1-wire weather firmware and connect a DS18S20 sensor.  I've got one of those
in the garage - it runs about 20 feet from the tracker to my freezer to make
sure the defrost heater hasn't broken again.  It's more accurate than the
on-board sensor and doesn't need any calibration.  It also isn't affected by
voltage drop on a long cable since it's a digital sensor - it generally
either works or doesn't, with no degradation in accuracy.

If you load the weather firmware with no external sensor connected, it'll
just report the on-board temperature in APRS weather format.  That lets you
get graphs on Findu.  If you do have an external sensor connected, you'll
still get the on-board temperature in the status text.  Check out
wx.findu.com/n1vg-3 for an example.

N1VG-3>APOT01:>Livin' in the fridge! 14.2V 23C

The board itself is at 23 degrees C, and the freezer is at -12 F.  The
status text always reports in C, so if you want F from the on-board sensor
you've got to run it in weather mode.  On the Tracker2 it's selectable.

As for calibration of the on-board sensor, it has a very linear response so
you only need a single-point calibration.  Just check the real temperature,
see what the sensor reports, and enter the difference in the temp adjust


> -----Original Message-----
> From: aprssig-bounces at lists.tapr.org 
> [mailto:aprssig-bounces at lists.tapr.org] On Behalf Of Drew Baxter
> Sent: Saturday, December 09, 2006 11:25 AM
> To: aprssig at lists.tapr.org
> Subject: [aprssig] House Temperature Probing
> It's winter again in the Northeast and that means fun things like 
> pipes freezing and heaters going out.
>   I'd be interested to set up something that reported every hour to 
> give me an idea of what the temperature was inside a camp I don't 
> often visit throughout the season.  If the heat fails, it could make 
> a big mess of things.
> I see the Opentracker has an onboard temperature sensor.  Does the OT 
> get hot in such a way that it could affect the readings from the 
> onboard sensor?
> Has anyone tried anything like this? :)
> Thanks.
> --Droo, K1XVM
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