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ZL3AI > APRDIG 28.01.04 13:28l 124 Lines 4469 Bytes #999 (0) @ WW
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Subj: TAPR Digest, Jan 25, 4/4
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From: ZL3AI@ZL3VML.#80.NZL.OC
To : APRDIG@WW
Subject: Re: etrex power
From: "Mike Yetsko" <myetsko@insydesw.com>
Date: Sun, 25 Jan 2004 21:28:39 -0500
X-Message-Number: 32
>Wanting to power my etrex off of the serial port on the laptop. Seems to
>be about 8.5 to 9 volts. Manual said that power cords drop voltage down
>to 3 volts. I know the older models are more forgiving. Anyone doing
>this? Can I just hack off the Garmin supplied cable....and the extra
>power wire will be in there ;-)
>Thanks,
>Robert
In a word, no.
Pretty simple. "No!"
If I remember right, you need a REGULATED 3v for the ETrex. Or whatever
the voltage is. And you need something on the order of 100ma or so....
You could pick up 5v at the Keyboard/mouse din connector and regulate that
down. Assuming your laptop can source enough current.
Mike
----------------------------------------------------------------------
Subject: eTrex power
From: Derek Koonce <derek@dkoonce.com>
Date: Sun, 25 Jan 2004 19:19:41 -0800
X-Message-Number: 33
USB port is 5V at 100mA in low-power and 500mA in high-power. The 4 dots
of connection on the back of a typical eTrex is ground, send, receive
and power. If the eTrex can handle 5V on the back, then I do not see why
you should not be able to power the eTrex from a NB - a typical NB
supplies 500mA. It is the un-powered USB hubs that only provide 100mA to
each of the 4 additional ports.
Derek
KE6JTP
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Subject: Re: etrex power
From: "Scott Miller" <scott@3xf.com>
Date: Sun, 25 Jan 2004 19:33:52 -0800
X-Message-Number: 34
Just to expand on this a bit... the (overpriced) Garmin cables that I've
seen have a serial connector and a cigarette lighter plug with an internal
3-volt regulator. They make it clear in the documentation that the cable
does the voltage regulation so you don't try to wire one up yourself and
feed it 12 volts directly.
There is no 'supply' pin on the serial port. You can sometimes power small
devices off one of the handshaking lines, but don't expect to pull more than
a couple of milliamps from the port.
Don't confuse this with setups like a TinyTrak + Digitraveler, where the
power supply provided to the tracker is fed through the serial cable to the
GPS. In that case, you're still providing an external power supply.
The keyboard connector will supply around 100 ma, which is probably pushing
it for some GPS receivers. Not sure about the eTrex - I don't have an
external power cable to test mine with. See
http://panda.cs.ndsu.nodak.edu/~achapwes/PICmicro/PS2/ps2.htm for more
keyboard port info.
Scott
N1VG
----------------------------------------------------------------------
Subject: Re: etrex power
From: James Jefferson <jj@aprsworld.net>
Date: Sun, 25 Jan 2004 21:43:29 -0600
X-Message-Number: 35
Okay, to make a long story short. YOU CANNOT APPLY MORE THAN 3 VOLTS TO THE 3
VOLT INPUT ON THE ETREX. You will fry it if you significantly exceede the 3
volt input.
Please see www.pfranc.com for details.
FWIW - I did a google search on "etrex maximum voltage" and there were a
handful of sites listed on the first page of the results that covered this.
-Jim
----------------------------------------------------------------------
Subject: Re: etrex power
From: "Mark A. Lewis" <mark@siliconjunkie.net>
Date: Sun, 25 Jan 2004 21:53:50 -0600
X-Message-Number: 36
Something of interest from http://pfranc.com/usb/etrex.htm :
11/26/2001 --- I tried this today and it worked with my eTrex - BUT - It
may not be OK for other models or other conditions I have not thought
about yet - but - I think it's a really great idea with lots of
potential so I'll publish it here for your comments.
I added 2 diodes to my USB converter and now it supplies both data and
Power to my eTrex! And it took me only 5 minutes.
I soldered 2 diodes in series to the bottom of the PCB and plugged in
our eD1 cable The diodes connect power from the USB port to pin 8 of the
DB9 connector. Our eD1 cable connects pin 8 to the power pin of a eTrex!
Cool huh? That's it! Nothing else needs doing, just add the 2 diodes. I
used two 1N4148's which are rated for only 100ma. Some other type may be
better. I connected them in series between the 5V USB supply and pin 8
of the DB9. The no-load voltage looks high at 3.8V but don't worry
because when the eTrex is turned on it instantly drops to about 3.14V.
---
END OF DIGEST
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