[aprssig] Tiny Telemetry

scott at opentrac.org scott at opentrac.org
Tue Aug 31 10:13:09 EDT 2004

At the risk of restarting some old arguments on what's considered
appropriate use of 144.39 and the APRS message formats, let me say that that
sounds like a bad idea.

The OpenTracker has 3 A/D inputs.  4 if you count the one used for energy
detect on receive.  One's normally wired to a temperature sensor, another to
the voltage divider, and the third is unused if you're not running in 1-wire
weather mode.  Right now, it'll report temperature and/or voltage in the
comment field.  I've had a couple of requests to add 4-20ma current loop
support to the other input, which I haven't done mostly because I haven't
got any sensors on hand to test it with.

If I can get a clear description of what people would like to see in a
telemetry encoder, I'll work on getting that ready in time for DCC.  I can't
guarantee it'll be able to fit GPS support in the same firmware, but it'll
at least work (like the weather version does) in fixed mode.

The new surface mount version is pretty small, and you can get power
consumption under 4ma @ 12v.  And it'll be a heck of a lot cheaper than a

So, if there's a telemetry feature you want, let me know - e.g., 4-20ma,
1-wire sensors, whatever.  I'll see what I can do.


-----Original Message-----
From: aprssig-bounces at lists.tapr.org
[mailto:aprssig-bounces at lists.tapr.org]On Behalf Of Robert Bruninga
Sent: Tuesday, August 31, 2004 5:27 AM
To: aprssig at lists.tapr.org
Subject: [aprssig] Tiny Telemetry

Need a small APRS gizmo for remote telemetry?

The pocket tracker which combines a TinyTrak
and a small 144.39 transmitter and a 9v battery
into a shirt pocket device (fits in an Altoids can)
is ideal.

Of course, it only processes GPS data, but wait!

For other purposes, remember that GPS data is
just numbers and there is nothing that says it
has to mean LAT/LONG.  So if you want to have
a quick way to get a unique telemetry system on
the air, just have your little project output a GPS
NMEA string but let the 13 or more digits mean
whatever you want.  THen decode them on the
other end...

Anyway, just a quick way to get some unique
telemetry on the air in a small off-the-shelf package...

de WB4APR, Bob

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