USB data and power cable for eTrex and Other things! Earthmate too!

04/19/03: A great idea from Andy in Australia: Because NiMh batteries are only 1.2V each, you can run your Garmin with 5 volt external power without running down the NiMh batteries! I wonder if the USB-G4 modification below (no diodes just a wire) would work with the other (round plug) Garmins? Of course you'll want to use our pD32 cable because it connects up both the power (via pin 9) AND data! And don't miss our combination deal and save: pUSB32 cable combination. Let me know if you try this. (for eTrex -- you'll want our eUSB1 cable combination deal. ) 

05/24/02
Hi Larry,
after looking at your power option for the USB converter I wanted to try this myself.
But instead of using two 1N4148 I use a 2.1 V zener diode. 
It works perfectly! 
Thanks for the hint.
Keep up the good work.

Carsten - Denmark
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.

Check out our eUSB1 cable combination deal. )

I plugged it into a USB hub attached to my new Windows XP system and it automatically configured itself as COM port 3. I ran the Garmin update to Ver 2.05. It "auto-found" COM 3 started up and auto configured to 115k baud, downloaded everything, and get this part --- everything worked! Yeeee-hha! I love it when that happens.

Let me know if you try this and what you think and how it works. Thanks.

NOTICE: A USB device asks/tells the Host (your PC) how much power it will be using so the Host can allocate it amoung the potential hundreds of USB devices connected to one port. A "high powered" device can request and get 500mA. Our USB converter device does not declare itself as a "high powered device". So what? Well, the above idea screws with the standard. But I don't see how it could be a real problem in the real world unless you are connecting lots of things to one USB port and have power problems. Standards and rules are good things but should not be abused for the wrong reasons. I don't see the advantage of remaining ignorant.

August 2002, Cliff Van Horn, modified our USB converter to supply power to his Earthmate via pin 9 of the DB9, no diodes needed. He sent this photo to me:

Hi Larry, ... I opened the case easily and soldered a jumper from the red input wire to the DB9 plug pin 9 circuit board connector. Works fine, a little less sensitivity the same as low batteries I imagine. In the car it still holds lock in 3D mode. I tried putting the batteries back in with the mod and it didn't fry anything. Do you think it is okay to run both? Would this increase the battery life while keeping the sensitivity up? (Hey, I know my way around a soldering pencil but mostly worked on the total system and not the basics) You are welcome to use anything I have written in all these emails and rewrite any of it as you wish for use on your web site. Am attempting to attach a couple of .jpgs which you are welcome to use also. I am now a totally satisfied customer!! Thanks again to both of you!! Cliff

Cliff is using our USB converter to connect an Earthmate to a Toshiba 1005 S157 XP Home Edition.

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