Garmin Etrex/Geko car power adapter

[festy]

Hi all,

Want to power your garmin from your car's cigarette lighter socket as cheaply as possible? Last night I converted an old mobile phone charger to an appropriate voltage for my Geko 201 (http://www.garmin.com/products/geko201/) in 15 minutes. Here's how it's done:

First, find a no-name mobile phone car charger. They're available from just about everywhere for a few dollars. I saw a bargain bin full of them for 50 cents each the other day at Dick Smiths. Don't worry too much about what kind of phone it's for, they're pretty much all the same inside.

I think mine was from an old Motorola or Nokia phone, not sure which as the plug had been ripped off the end.

[festy]

Unscrew the end, remove the fuse and prise the case open. It wasn't glued together and came apart easily. The main component on the board is a MC34603A (http://www.addmtek.com/product/amc34063a/amc34063a.htm) switch mode power supply chip. The circuit is simple and pretty much straight from the datasheet.

Now locate R3, it should be just below the IC.

[festy]

unsolder resistor R3 and throw it away. This is the resistor that sets the output voltage. It needs to be replaced with one that will set the output voltage as close to 3v as possible.

[festy]

I didn't have much of a choice of resistors with me so a bit of trial and error with different resistors and a multimeter followed. First I tried a 1.5K ohm resistor, but that lowered the voltage too far, to 1.5v. Sticking a 100 ohm resistor in parallel with it produced as close to 3v as I thought I could get.
Close the case back up, stick the fuse in and screw the end cap back on.

Stick a Pfranc (http://www.pfranc.com/) plug on the end, and you've got a neat, easy car adapter for your GPS for under $15.

[bandy]

thanks for your very detailed method of making the adaptor. I intend to make one and I will let you know how it goes. My Question is can you modify anything to run my laptop of the car cigarette lighter. It runs on 16 volts dc . thanks in advance Bandy

[festy]

What brand/model laptop?

[bandy]

Thanks festy for your reply. It is an Ibm Think pad type 2626 16 volt 3.36 A on the back also it is 400 mhz regards Bandy

[HappyJacky]

Hi guys,

just downloaded the wiring diagrams for the Garmin range of GPS units. Thought it might be an appropriate addendum to Festys' info

cheers
Barry (aka HappyJacky)

Bugga might help to actually attach the document huh

double bugga, can't upload a PDF file :confused:

[Craigus]

hehe.. To add a pdf you'll need to zip or rar it first

[HappyJacky]

Okay, lets see if it will work this time!

On closer examination, the diagrams don't show which pin on the DB9 plug is the power pin. Am going to contact Johnny Appleseed GPS for info today.

Will let you know when I find out.

(Thanks craigus for fixing the PDF upload)

Cheers

[HappyJacky]

Good news,

spoke with a young bloke at Johnny Appleseed in Brisbane.

Bad news:

The data cables only have THREE wires in them, so there is no way to make up your own power adaptor using your existing data cable.

So if you want to power your Garmin GPS whilst its connected to your laptop, you HAVE to buy the Garmin cable or buy the plug that festy gave the link too earlier and make a whole new cable.

[festy]

They might only have 3 wires in them, but if it's anything like waste of money one I bought with my Geko, it has the fourth pin on the gps end, just no wire in the cable. There's nothing stopping you from unscrewing the plug and soldering an external wire to the power pin and run 'outboard' power :) It does work, but considering you can make your own power/data cable for under $10, I just made a whole new cable.

Hint - an old serial mouse has a DB9 and a nice thin cable, and can usually be got for free.

[willow153]

Hi All
Here is a guy in WA with some excellently priced generic gear on Ebay


http://cgi.ebay.com.au/GARMIN-eTrex-eMap-Geko-Goldplate-Data-12V-Cable-eCombo_W0QQitemZ5796798673QQcategoryZ34290QQrdZ1QQcmdZViewItem

[Nicko]

You can buy a complete one from GPS Australia for about $25 without the hassle of driving to DSE, driving back, finding a soldering iron and solder, a multimeter and two resistors etc etc and possibly risk destroying the Etrex from a mixup in the wiring or misread the voltage output... If you got the money to waste time then you got the money to buy a proper one!

[festy]

thanks for your very detailed method of making the adaptor. I intend to make one and I will let you know how it goes. My Question is can you modify anything to run my laptop of the car cigarette lighter. It runs on 16 volts dc . thanks in advance Bandy

have a look at http://www.gpsaustralia.net/forums/showthread.php?t=439
$23 and an hour's work.

[Nicko]

Why bother saving yourself $10? You can buy the same item from GPS Australia for $25, saving time and money by not having to buy bits and peices, petrol, wear and tear on your car and the risk of shorting your GPS!