PDA GPS power issues (i.trek Mouse)

[Mark Morissette]

Hello everyone.. I've posted this question in a few different NG's
and forums, so appologies in advance for anyone reading it again.

Anyow..

I have a Sony Clie TJ25 Palm-OS PDA that I recently purchased an
i.trek mouse GPS receiver for from Semsons & Co. in the USA. I'm
located in Canada, myself...if that matters.

Anyhow, I plan on using the GPS mainly for general-aviation navigation
as well as the odd Geocaching adventure.

However, I have discovered a problem - The i.trek unit will *not* work
unless the cigarette lighter power plug (Which is part of the PDA to
GPS interface cable) is plugged in. I didn't know this ahead of
time.

Now, this presents several problems:

First, when Geocaching, I'm obviously not near a 12v cigarette lighter
plug.

Secondly, not all of the rental aircraft that I fly are equipped with
cigarette lighter power sources. Additionally, most planes I fly
(Cessna's) are a 24v power system, and I'm unsure yet if the power
adapter that is part of the i.trek PDA interface cable will accept
this high of a voltage. I'd hate to fry the GPS itself, and the PDA,
finding out the hard way.

In a pinch, I can band-aid some sort of "portable" 12v power supply
using non-spillable batteries and some sort of backpack for
portability sake, but it starts to get cumbersome at that point.
Additionally, everyone here knows that every pound counts - carrying
around extra batteries to power a GPS isn't ideal. As it is, with
myself and another sturdy individual in a 152, we're already running
less then 3/4 tanks to stay within W&B. :-)

I know that other "direct" cables for mouse-style GPS units actually
power the GPS from the PDA (Which is what I desire), but I'm stuck
without that option apparently at this point.

I'm wondering if anyone else has run into this problem, and what the
solution might have been? Can I buy a PDA connector for my Sony from
eBay, and hack it into a direct cable successfully? Is there some
sort of modification possible to the cable I have now to enable
powering the GPS from the PDA even when it's not plugged into the
cigarette lighter?

I know that many mouse GPS units *can* be powered directly from the
PDA..but unfortunately mine doesn't appear to be one of them..yet.

I'm quite happy with the actual i.trek unit at this point, regardless
- it's been performing excellent to date, although I have not yet
taken it airborne.

Regarding batteries, the TJ25 has an *excellent* battery onboard, and
even with the GPS draw I would still except several hours of runtime -
fine for 90% of my flights.

Anyone have any "Been-there-done-that" stories, or solutions?

Any assistance appreciated!

Email me or respond here, either is great. Any emailers will need to
de-munge my antispammed email address first.

Thanks everyone!
Mark

[Newps]

If your PDA has bluetooth then that is the only way to go. If it
doesn't then see if you can get bluetooth with an SD or CF card. Then
sell your GPS and get a wireless bluetooth GPS. I use an Altina GPS and
it works great, about 10 hours on a charge. If you have to have a wired
GPS then do a Google search for a cable. My first PDA I used a cable
between my Garmin Pilot III and my PDA. The cable had a jack for
external 12V power but you didn't have to use it.



Mark Morissette wrote:

> Hello everyone.. I've posted this question in a few different NG's
> and forums, so appologies in advance for anyone reading it again.
>
> Anyow..
>
> I have a Sony Clie TJ25 Palm-OS PDA that I recently purchased an
> i.trek mouse GPS receiver for from Semsons & Co. in the USA. I'm
> located in Canada, myself...if that matters.
>
> Anyhow, I plan on using the GPS mainly for general-aviation navigation
> as well as the odd Geocaching adventure.
>
> However, I have discovered a problem - The i.trek unit will *not* work
> unless the cigarette lighter power plug (Which is part of the PDA to
> GPS interface cable) is plugged in. I didn't know this ahead of
> time.
>
> Now, this presents several problems:
>
> First, when Geocaching, I'm obviously not near a 12v cigarette lighter
> plug.
>
> Secondly, not all of the rental aircraft that I fly are equipped with
> cigarette lighter power sources. Additionally, most planes I fly
> (Cessna's) are a 24v power system, and I'm unsure yet if the power
> adapter that is part of the i.trek PDA interface cable will accept
> this high of a voltage. I'd hate to fry the GPS itself, and the PDA,
> finding out the hard way.
>
> In a pinch, I can band-aid some sort of "portable" 12v power supply
> using non-spillable batteries and some sort of backpack for
> portability sake, but it starts to get cumbersome at that point.
> Additionally, everyone here knows that every pound counts - carrying
> around extra batteries to power a GPS isn't ideal. As it is, with
> myself and another sturdy individual in a 152, we're already running
> less then 3/4 tanks to stay within W&B. :-)
>
> I know that other "direct" cables for mouse-style GPS units actually
> power the GPS from the PDA (Which is what I desire), but I'm stuck
> without that option apparently at this point.
>
> I'm wondering if anyone else has run into this problem, and what the
> solution might have been? Can I buy a PDA connector for my Sony from
> eBay, and hack it into a direct cable successfully? Is there some
> sort of modification possible to the cable I have now to enable
> powering the GPS from the PDA even when it's not plugged into the
> cigarette lighter?
>
> I know that many mouse GPS units *can* be powered directly from the
> PDA..but unfortunately mine doesn't appear to be one of them..yet.
>
> I'm quite happy with the actual i.trek unit at this point, regardless
> - it's been performing excellent to date, although I have not yet
> taken it airborne.
>
> Regarding batteries, the TJ25 has an *excellent* battery onboard, and
> even with the GPS draw I would still except several hours of runtime -
> fine for 90% of my flights.
>
> Anyone have any "Been-there-done-that" stories, or solutions?
>
> Any assistance appreciated!
>
> Email me or respond here, either is great. Any emailers will need to
> de-munge my antispammed email address first.
>
> Thanks everyone!
> Mark
>

[Peter]

Mark Morissette wrote:

> Hello everyone.. I've posted this question in a few different NG's
> and forums, so appologies in advance for anyone reading it again.
>
> Anyow..
>
> I have a Sony Clie TJ25 Palm-OS PDA that I recently purchased an
> i.trek mouse GPS receiver for from Semsons & Co. in the USA. I'm
> located in Canada, myself...if that matters.
>
> Anyhow, I plan on using the GPS mainly for general-aviation navigation
> as well as the odd Geocaching adventure.
>
> However, I have discovered a problem - The i.trek unit will *not* work
> unless the cigarette lighter power plug (Which is part of the PDA to
> GPS interface cable) is plugged in. I didn't know this ahead of
> time.

Is the GPS you have the one described on:
http://www.semsons.com/itmousgpsrec.html

According to that page, it needs about 5V @ 90 mA. Rather than mess
with the PDA cable and also risk running down the PDA internal battery,
I'd just hook it up to a holder with 4 AA cells. If you'll use it quite
a bit then NiMH rechargeables would be the best bet and a set of 2300
mA-hr cells would power it for over 24 hours.

[Mark Morissette]

On Tue, 15 Mar 2005 20:42:04 -0700, Newps > wrote:

>If your PDA has bluetooth then that is the only way to go. If it
>doesn't then see if you can get bluetooth with an SD or CF card. Then
>sell your GPS and get a wireless bluetooth GPS. I use an Altina GPS and

Two problems:

First, my PDA isn't bluetooth capable.

Secondly, being a Sony PDA, it uses Sony's (admittedly stupid)
proprietary Memory Stick format. Not only is finding a bluetooth
adapter to fit in a Memory Stick slot nearly impossible, but the last
problem is that I have a 256k memory stick in there now, which is
pretty much required due to the limited memory of the TJ25 to begin
with.

It's kind of a vicious circle... :-)

I don't mind the cables, really, it's no big deal, but I *would*
really like to power from the PDA..

[Mark Morissette]

Hi Peter;

>Is the GPS you have the one described on:
>http://www.semsons.com/itmousgpsrec.html

That's the one..just received it a few days ago. For anyone
interested, I had excellent service from that Company, highly
recommended.

I just wish that they would clearly note on the page for that unit
that when used with the included PDA connector, it *requires* that the
cigarette lighter be plugged-in for the GPS to function. :-)

>According to that page, it needs about 5V @ 90 mA. Rather than mess
>with the PDA cable and also risk running down the PDA internal battery,
>I'd just hook it up to a holder with 4 AA cells. If you'll use it quite
>a bit then NiMH rechargeables would be the best bet and a set of 2300
>mA-hr cells would power it for over 24 hours.

Hmmm....excellent idea. I have about 48 NiMH AA's around the house,
ranging from 1800 to 2100 mA-hr's...so that would work.

The majority of my flights are <1hr each way, so that would fit the
bill...and extra cells are easy to carry in the flightbag.

I intend to carry the PDA charger with me during flights, so if
required, I can plug-in at point-b to recharge before the return.. My
Sony unit does charge fairly quickly.

Regardless, I would *still* like to sort out a way to power the GPS
directly from the PDA on occasion, as like I mentioned, carrying
around another battery pack (Even a small 4AA pack, admittedly)
becomes more cumbersome.

From experience, the PDA will run for 6 to 7 hours with active use,
and full backlighting - it has a great (and replaceable) Lithium-Ion
battery. I can't immagine that even with a 90 mAh draw from the GPS
that it would seriously impact the battery life beyond a still
functional time for my needs.

Thanks for pointing out that the GPS's voltage requirements are
mentioned right there on the dealers page, however.. I failed to
notice that - I've been looking for that exact information for a few
days now (in order to sort something out to solve this problem), and
believe it or not it's actually not included with the unit itself, nor
could I find it anywhere else.

Silly me, never thought to check right back at the source.. :-)

[Mark Morissette]

>However, I have discovered a problem - The i.trek unit will *not* work
>unless the cigarette lighter power plug (Which is part of the PDA to
>GPS interface cable) is plugged in. I didn't know this ahead of
>time.

>However, I have discovered a problem - The i.trek unit will *not* work
>unless the cigarette lighter power plug (Which is part of the PDA to
>GPS interface cable) is plugged in. I didn't know this ahead of
>time.

For anyone who is interested, I remedied this problem myself, after
not finding any immediate solutions anywhere else.

5 Years of electronics courses are paying off.. :-)

Basically, I pulled the GPS to PDA cable apart at the PDA connector,
and at a junction connector, and start probing with my multimeter...

The circuit that was providing power to the PDA while the cigarette
lighter was plugged in did *not* backfeed power when the cigarette
lighter power source was removed, but the GPS was left on. If it
did, it would have backfed the required +5v to the junction box, and
hence, to the GPS...

However, one of the other pins on the GPS connector *did* have a ~+5v
output when the PDA was on..or off, for that matter..but that wasn't
terribly important. It seems that this was a direct connection to
the PDA battery from this pin.

So, I got busy with the soldering iron, and did the following...

After opening the PDA end of the connector, I drilled a small hole in
the housing to allow two small guage wires to pass through. I
soldered one end to the constant +5v pin (Which was unused), routed it
through the cover to a small switch mounted externally, and then ran
the other wire back into the housing, and soldered to the +5v feed
wire that supplied voltage to the PDA when the cigarette lighter is
plugged in.

With the switch closed, the PDA now backfeeds power to the small
junction box, which in turn feeds the GPS successfully.

When I want to plug in the cigarette lighter plug, I simply open the
switch, and things revert to normal.

The reasoning behind the switch is that I'm unsure what will happen if
voltage is fed back to the alternate circuit I used to draw power
from. My indications are that this circuit connects *directly* to
the PDA battery - if voltage is backfed to this circuilt via the
cigarette lighter charger, it would be bypassing any charging circuits
within the PDA. Also, voltage would now be provided at 2 points on
the PDA connector.

Maybe no problem...possibly a big one. The switch isolates the
changes I made, so there is no concern.

Works like a charm - the PDA now successfully powers the GPS for about
2 hours and 20 minutes on a full charge. A flip of the swich, and the
PDA and GPS is powered by the cigarette lighter again, and the PDA
hapilly charges itself.

Problem solved!

[Darrel Toepfer]

Mark Morissette wrote:

<snip>
> 5 Years of electronics courses are paying off.. :-)
<snip>
> Works like a charm - the PDA now successfully powers the GPS for about
> 2 hours and 20 minutes on a full charge. A flip of the swich, and the
> PDA and GPS is powered by the cigarette lighter again, and the PDA
> hapilly charges itself.
>
> Problem solved!

Wouldn't a single diode been cheaper and easier or were you afraid of
the voltage drop across it?

[Mark Morissette]

>Wouldn't a single diode been cheaper and easier or were you afraid of
>the voltage drop across it?

True enough...never really thought of doing it that way, actually.

The first thing that came to mind was the manual switch..which is the
way I went.

Electronics class was a long time ago... Alot of what I learned was
pushed out of memory when I was studying for my pilots licence - my
brain was full. <grin>

If the need arises to replace the switch for some reason, then yes, I
would have to say that a Diode would serve the same purpose,
automatically. The light bulb just never came on bright enough this
time. :-)

[Darrel Toepfer]

Mark Morissette wrote:

> Electronics class was a long time ago... Alot of what I learned was
> pushed out of memory when I was studying for my pilots licence - my
> brain was full. <grin>

Same here... In that process now...