How to assemble the ePlug, and make a cable for your Garmin eTrex.
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New Feb 2003: How to make a iPaq Garmin combo cable to interconnect and power both units. First read the Warnings below.

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#1) You can burn up your Garmin eMap GPS with a power cable if the voltage supplied to the power line exceeds 3.3 Volts DC. My eMap shuts off below 2.5V and the screen starts to go dark above 3.5V. My eTrex, on the other hand, is happy from 1.75V to 6V! (*see note1) I hooked it to 6VDC for 2 hours. It works fine! I think 5V is no problem(*see note1) - except for the eMap, and then it doesn't hurt it, just makes the screen very dark and unreadable. [Note 1: Mid 2004 things changed! The new redesigned yellow eTrex (Ver 3) is NOT happy with 5V+. It causes no harm but the screen goes dark.]

#2) Put a fuse in your power cable to avoid a fire. Cigarette lighter sockets have enough power to light-up a cigarette, your cable, and your life (as you watch your car go up in flames from the trail head because you removed your cool home made cable to take your GPS on a hike and it shorted out on a chrome door handle... bummer.) Not likely with power and ground pins at opposite ends, but possible. Your GPS needs just a little power so you can use pretty small wire, which is nice, but make sure the fuse is right for the wire. You want the fuse to blow before the wire gets hot. So can anyone tell us what size fuse and what size wire? Answer: "... for the Etrex the rating of the fuse needs to be 300mA"; (Ido Bar-Tana -5Apr01 X-10 guy)   AND: "... for the smallest wire that will carry 300mA, go here."; (Richard Matthews -13Jun01)
It looks to me like a 300mA fuse and 26 AWG (0.40mm) wire will work!

The best assembly instructions are being done by other people around the world:
First feed the wires through the holes in the mid section then solder or crimp (or both) the pins to the wires. Then one at a time place each pin in the bottom to hold it and with your thumb nail holding it in the slot, bend it up 90 degrees (see photo below). Then use the safety pin idea for final assembly.

The "Safety Pin" idea:

I don't have assembly drawings yet but Mr. Naoya in Japan sent me a great idea that makes assembly much easier. I call it the "Safety Pin" idea because a fellow in Kansas borrowed a safety pin from his wife and told me it worked really great! Here is the drawing Mr. Naoya sent to me:
Saftey Pin idea.

Thanks very much Mr. Naoya. A couple of professional cable manufactures told me this idea has made assembly much easier!

How to make a PC cable:

I put marks right in the mold to identify the pins. The outside pins are for power. The inside pins are for data. The outside pin marked "-" is ground. Ground is shared for both power and data. Data-in is next to the + and data-out is next to the -. Data out has a round shiny mark near it.

Both eTrex and eMap can take the RS232 voltage levels no problem, however, do not supply power to the + line in excess of 3.3 Volts DC. When someone offers us some power supply ideas I'll add them here.

To connect to a PC just attach a DB-25 or DB-9 female connector to your cable: On the DB-25 pin 2 is "data-out" (of the PC) hook it to "data-in" of the Garmin, and pin 3 is the PC's "data-in" ... hook it to the Garmin "data-out" (see above), and lastly pin 7 is ground. The DB-9 has different pin assignments ... swap them! Swap 2 and 3....pin 5 is ground.

Several people have told me that a dead mouse tail makes a great cable.

How to make a Power cable:

Warning! Do not exceed 3.3 Volts DC! Several people have told me the official range is 3.15VDC +/- 0.15V. I also hear the eTrex uses a MAX 1677 DC-DC converter chip inside. If the external supply voltage goes lower than 2.8V then the internal batteries are used. I've received several power supply designs. I like the ones that use a 3 pin regulator but I hear they run pretty hot. One is a LD1117V28 with a .1uF cap on the input and a 10uF on the output. Another is a LM317T ($1.99 at radio shack) with two resistors (560 ohm and 380 ohm) and another using the LM317T again but with only one 100 ohm resistor. So until I figure out which is best I don't want to recommend any just yet. Garmin uses a switcher based on a MC34063 8 pin IC and a bunch of other parts including caps resistors and a large donut shaped inductor. Looks like the inside of a PC's power supply. Since a car's battery can be as high as 18Volts, maybe it's a good idea to use a switcher design. Not easy for the DIY guy.

Let me know if you come up with a "cool" idea for this "hot" power problem. Thanks everyone for your support!

Our Pfranc in Estonia has a great eTrex hacking page! A DIY connector and power supply circuits.

POWER from USB? Yes. It's 5 V and you can take 500mA per device if the device declares it's a "high power" device to Windows (but - who cares? --- unless you have lots of devices competing for limited host power). See what I did to power my eTrex from my USB-serial converter here. We've made a bunch of these for other people and it seems to work just great! We can't make it a production item because someone would freak out and make us stop breaking the rules - oh well. I'll modify one of our new units for you (maybe) for the unit cost plus $10 if you can't do it yourself. (10/1/02) larry.

See here for how to get power from your PC. -- like from almost everywhere possible - except he did not mention USB the last time I looked.

Also don't miss my new cool idea for Data and/or Power cables. and "POWEREADY" cable idea where I include a wire from the Garmin power pin to a pin of the DB9 so you can "insert" power and take advantage of our great cables. We "KEY" the cable to the Garmin model and assign different pins of the DB9 for different voltages so you won't burn up a Garmin! AND one could make a 3 voltage data+power "inserter" that would work with all types of Garmins with just one plug! (using our 3 types of cables). A little confusing but very cool - I think.

So you want POWER and DATA?

No problem.  Just do it.  The ground pin on the GPS is used for both power and data.  It is no problem for the GPS, power supply, and computer to share the same ground.  Matter of fact, it's a good thing!

A Garmin to Garmin cable.

I've been told that because the eTrex and eMap do not have a SEND and RECEIVE command mode you cannot do Garmin-to-Garmin data transfers .... bummer....

Macintosh? We didn't forget the Mac! Thanks to Pfranc Christer in Sweden! Check it out here: Clove Technology home page. Not only does he tell you how to make a cable for your Mac, he will send you software too!

Here is a neat web site showing how to assemble our ePlug and making a cable for the eTrex: WeetHet.

Please send any comments, help with links, facts, words, spelling, syntax, format, presentation, etc... (even if a comma is out of place).... E-mail to: Click here. .... thanks!

IPO: 8/2000, last update: 8/2000 ... My thanks (and free connectors) go to these people for their great ideas and editing help: Mr. Naoya Kuno, Mr. Daniel Siu, Mr. Takahiro Sato, Mr. Kazuo Nakazawa, Rob Smeets, Dan Diehlman, Dale DePriest, Dr. Antonio Rodriguez Franco Pfranc of Spain, Doug Miller, Troy Ellis, Mr. Isao Ota, ... , and many others.
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