[aprssig] RS Digitravelr Power Mod

[Wes Johnston]

A word about the digitraveller... if you leave batteries in the unit (it can be powered up and down by the serial cable mod with or without batteries)...  And it is good to leave batteries in the unit because it keeps the real time clock running and warm starts take 30 seconds.... vs if you leave the batteries out and the unit has to cold start for 3 minutes or more each time.

Here is the gotcha.... since the batteries don't accept a charge, they eventually run down.  When they get too low, rather than dieing peacfully, they will corrupt the memory in the GPS... requiring manually removing the batteries and making the GPS reset.  This will probably happen every 3 months in regular automotive use.

So, if you need fast starts on the GPS leave batteries in it but plan on replacing them every 2 months proactively.  If you want a reliable GPS that starts every time, leave the batteries out and live with 3 minute startup times.

Wes

----- Original Message -----
From: Lance Cotton <joe at lightningflash.net>
To: TAPR APRS Mailing List <aprssig at lists.tapr.org>
Sent: Sun,  2 Apr 2006 12:45:03 -0700
Subject: Re: [aprssig] RS Digitravelr Power Mod


> Chuck Gooden wrote:
> > Purchased a Radio Shack Digitraveler GPS off ebay a few weeks ago and
> > would like to get it working for APRS use in my van.
> > 
> > Could someone please provide the details on the Power mod for the Radio
> > Shack Digitraveler GPS unit.  Looking at:
> > 
> > http://w5ac.tamu.edu/~kj5o/digi_traveler_mod.html
> > <http://w5ac.tamu.edu/%7Ekj5o/digi_traveler_mod.html>
> > 
> >>From the picture, it appears the power regulator is simple soldered to
> > the bridge rectifier output leads with a wire connected to the left most
> > lead.  Is this correct or is there more to it?
> 
> What the picture illustrates is how to modify the digitraveler to accept 
>   up to 35V DC on a spare wire in the RJ11 connector. (In the 
> digitravelers I received, this was the RED wire in the included cables, 
> YMMV)
> 
> When this mod is in place, power can be supplied in the same connector 
> that serial data goes over. The reason the red wire was chosen (it's the 
> Digitravelers RS232 RX wire) is that there must be some non-zero voltage 
> on that wire to wake up the digitraveler. Make sure you don't also 
> connect the red wire at the other end of the cable to a computer's 
> RS232-TX wire AND 12V at the same time!
> 
> With this mod in place, I think there may be some interference if you 
> also put AA batteries in the digitraveler. A diode placed somewhere 
> ought to fix that, but I never took the time to think about it, since I 
> never plan to use batteries in mine.
> 
> Soldering to the rectifier outputs was chosen just because it's an awful 
> convenient spot to solder to.
> 
> -Lance KJ5O
> 
> -- 
> J. Lance Cotton, KJ5O
> joe at lightningflash.net
> http://kj5o.lightningflash.net
> Three Step Plan: 1. Take over the world. 2. Get a lot of cookies. 3. Eat 
> the cookies.
> 
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