DIY GPS Charging cable

[Eric Walstad]

I created a photo album showing how I built a charge cable that allows me to charge my Garmin Edge 500 without resetting the device. I have used this cable design on many Brevets by plugging it into the USB port on my Luxos U dynamo light.

Disclaimer: I'm no expert, I just followed instructions I found on the 'net. The cable has worked flawlessly for me so I thought I'd share the information here, hoping that others find it helpful.

Use at your own risk!

https://flic.kr/s/aHsjXKRFM8

Eric.

[Massimiliano Poletto]

Very nice!

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[Willie Hunt]

With the 47K ohm resistor in series there is so little charging current that all that cable it doing is making the Garmin 500 tell you it's charging, when in fact it will be still discharging for all practical purposes as fast as without the cable plugged in.

I have not tested a Garmin 500, but on a Garmin 800 all you have to do is connect the GND (black) and +5V-USB (red) wire to a 5 volt, 0.5 Amp power source (that what you get in the little charger units).  This does not require any micro surgery on the plug.  The data lines (normally green and white) are left disconnected.  If your charger drives the data lines, then the Garmin will think it's connected to a computer and reset.  

Also, there are tons of these "turn key" chargers that should work properly with a Garmin on Ebay: http://www.ebay.com/sch/i.html?&_trksid=p5713.m570.l1313.TR0.TRC0.H0.Xbattery%20powered%20usb%20charger&_nkw=battery%20powered%20usb%20charger&_from=R40

Willie

[Rick Gordon]

I'm probably missing the boat on the problem encountered here. I have an 810 and I have two Garmin cables. One came with the 810 and the other is probably from a 500 I had.  It might also be from an Oregon I have. Anyway when plugging into a wall outlet or plugging it into a external usb battery the 810 charges and operates. I can shut down the 810 and it will charge while it is off. I have the Luxus U but have not yet used it to charge the 810 with either of the two cables. There just has not been the need yet and I am just getting used to the Luxus U anyway.

I'm just wondering why it is that a cable needs to be made. Is it because the 500/800 and their cables work different than the 810 and its cables?

Just curious about the issue.

Rick

[Eric Walstad]

My experience with the Edge 500 and using a standard USB cable

1. Record a track on a 400k Brevet
2. Charge GPS at the Hopland mini mart while eating pizza and having a beer.
3. Notice that when the GPS is plugged into the charger it resets itself; the track is no longer recording and the display changes to only read "Charging"
4. Before continuing the ride, turn back on the GPS and start recording a new track.
5. Repeat each time you have the opportunity to recharge the GPS while on the ride.
6. After the ride to join the two or more GPS track files using a combination of online services and software.

With a modified cable, #3 - #6 go away.

Willie, I haven't measured the amperage when charging but I will on the next one I build. However, my experience is that it charges relatively quickly and I am able to charge and operate the GPS while riding throughout the night with my Luxos U charger while the light is on. It works for me.

Eric

[Rick Gordon]

Eric,

In case I run into this issue with my Garmin 810 or some other Garmin in the future - by standard USB cable do you mean the one supplied by Garmin or one you purchased. In my case, I can only state that the one that came with the 810 works fine.

Rick

[Eric Walstad]

By standard I mean one that does not have a resistor between pins 4 & 5. I suspect that's pretty much all of them including the cable that came with my Garmin.

Before I started digging around for a solution to my charging problem I tried a few different usb cables I already had but didn't find any that worked for me.

Eric

[Rick Gordon]

I guess it must be an issue with the 500 and maybe the 800 cables. Hopefully if someone has had problems with the 810 cables they will chime in here.

Rick

[John Guzik]

As far as I know the extra resistor is only needed for the 500 and allows the 500 to not reset and continue to function as a GPS while charging. If a standard cable is used the 500 will reset and go into charging mode when plugged in (e.g. you can't use it as a bike computer in anyway, aka a brick). This is a known REALLY ANNOYING issue with the 500 and has been covered in various other threads on this forum.

As far as I know the 800 and 810 can use a standard cable and will work as a GPS while charging. 

As Eric shows the modified cable adds a 47Kohm resistor between pin 4 of the mini USB connector and ground (pin 5). Mini USB (and micro USB) connectors have 5 pins, USB A/B connectors have four [I won't even go into USB 3.0]. Pin 1 and 5 are +5V, 2 and 3 are D- and D+ [aka data] and pin 4 usually labeled as sense.  The cable Eric made has the +5V and GND pins connected from the mini to the corresponding pins on the USB A plug (pin 1->1, pin 5->4) so the charging circuit gets the full 5V. There is no resistor in series with the charging circuit, the resistor is between GND and sense.

I use a gomadic charger on my rides and it comes with replaceable tips which one of them includes the resistor so the 500 works as a GPS while charging. I have been running into trouble as my USB connector is slightly damaged as sometimes it will reset anyway when plugged in. Also the gomadic uses 4xAA batteries, and if they are not fresh the Garmin may also reset.

I have often thought of opening the 500 and soldering on a larger battery (or at least adding some leads). The stock 500 battery is a li-ion 3.7V 700mAH so a 2500mAH or 4400mAH battery would extend its life quite nicely. This would require removing the internal battery and going with an external battery (although exposed li-ion battery and rain may not mix well)

Maybe I'm better off buying an 810.

I do have a question for Eric, how well does the adafruit connector fit into the 500? There is a slight ridge on the 500 and I was worried that an over-sized connector may not fit. Also does it fit snugly (aka does it fall out easy). I charge while riding and my current gomadic connector does not fit too well, so sometimes in falls out (and resets the 500). Like I said maybe I'm better off with a 810.

John

 

[Eric Walstad]

Hi John

The Adafruit connector has a snug fit in the Edge 500. I have never had it fall out. One minor annoyance of my Bar Fly handlebar mount, though, is that with the cable plugged in the gps has to sit slightly rotated to about "1:00 o'clock" to accommodate the cable. But it is still quite functional.

I like your idea of swapping out the battery for one with more capacity.  Mine still holds a decent charge so I'm not ready to risk tearing into the device yet. In a year or so when the battery degrades I'll give it a try!

I ordered more of the connectors from Adafruit and will have some extras. I'm happy to share them if someone wants to give this a try.

Eric

[Patrick Herlihy]

Yeah..  I can use any cable on my 800 and it will continue recording while charging. 

That wasn't the case with my 705 which would reset as described in this thread.

[Willie Hunt]

Right, I could not see that he had the resistor leg doubled over on itself and underneath the resistor body in the photos.  That's was the "missing" connection for the GND and all the charging current.

As far as opening LiIon powered equipment and installing a larger cell, I've done that to cell phones, music and video players, and it's works great.  You may need use some other charger as the internal chargers put out little currrent and they often have timeouts after a number of hours.  If you seal the leads coming back through the shell, and or conformal coat the electronics inside the unit, you will not have a problem with rain.  I've coated non water resistant music players and they have held up fine in hours of driving rain.  I highly recommend Dow Corning 1-2577 for this purpose.  Just be careful with connectors and getting the coating under the dome buttons as it may insulate a connection that you needed!

Willie

On Wednesday, April 30, 2014 8:10:49 AM UTC-7, John Guzik wrote:

[Robert Sexton]

Here be dragons.

The issue is whether you can charge the device while it records a track.

The Garmin 500 will not do this with a standard usb cable. It will
detect the charger and stop recording the track.

USB Mini-B connectors include a 'Sense' pin that isn't hooked up on most
cables. The Garmin 500 uses the sense pin to detect a Garmin-Approved
charger. You can modify a USB cable yourself (assuming the
connectors are not moulded), or you will need to buy a charge cable that
includes the sense resistor.

Gomadic sells them pre-made:
http://www.gomadic.com/garmin-edge-500-portable-aa-battery-extender.html

- Robert

[Gintautas Budvytis]

First of all, Eric thanks for the mini USB part you gave me. Your instructions are great! It's a nice 15min project and the result is a working charge cable for Garmin Edge 500. When I say working, it means the unit is charging while it is also recording the data.
I was on a quest (to China) to find a charge only cable for awhile now. You should see my collection of cables. All of them are "charge-only" (not data) cables but will not work with Garmin 500 unit, because the cable MUST have 47K resistor (for 500 unit) between pins 4 and 5 on the mini USB.
Just a few notes:
- make sure you identified connector pins correctly (in Eric's picture, for the part he uses pins are 5, 4, 3, 2, 1 when you look from the back, and they are in a tricky 2-3 formation, not all 5 in a line);
- universally accepted colors of wires (red/black) may not be used in "artful" sweatshops of China. My cable had pink wire instead of red (for +5V) and white wire not black (for GND). Have you voltage measuring instrument ready.

Next project for my Garmin 500, a charge cable with 90 degree mini USB connector. I've mounted my unit on my bike's stem, as probably most of you did and the space is tight.

GB

On Tuesday, April 29, 2014 9:49:35 PM UTC-7, Eric Walstad wrote:

[Jenny Oh Hatfield]

Eric was kind enough to lend me his cable to see if I could get it to work on my Garmin 510. Alas, no luck (I need to return it to you, Eric!) -- its brains just seem to get scrambled when plugged / unplugged into the Luxos U. (Or when I stop for a prolonged period of time or take a wrong turn.) 

As I use Cyclemeter on my iPhone5, I just mounted it in a special Timbuk2 case on my stem and ran the app during this weekend's Davis 400k. Worked like a charm and had no issues documenting the entire ride even while plugged in the entire time!

Cheers,

Jenny 

[C. Duque]

Would an 90° adaptor or better yet one that swivels 360°? I have both kinds you are welcome to borrow them and see if they work. Both are from mini USB to regular USB (male) and also have one that swivels that is mini to regular USB (female) They are probably available from mini USB to *female* mini USB online; I get all that stuff from dx.com a chinese site that is cheap and offers shipping but it takes a while to receive the stuff. 

Let me know, I can bring them to the final control of next weekend's 600k. I am working the 11am-3pm shift.

Carlos

[Gintautas Budvytis]

Yes, 90° adapter should do. Not the right angle (or left angle), or as they call "Motorola style" because the space is really tight. This is not ideal, but might work:
http://www.alibaba.com/product-detail/factory-direct-wholesale-90-degree-usb_937164418.html

I prefer this style, but without a cable:
http://www.alibaba.com/product-detail/Free-sample-90-Degree-Mini-USB_1062802847.html

dx.com is a good site (especially is you planning a wedding, I guess ;^) but I was not able to find 90° "male" mini USB to "female" mini USB adapter (sounds so wrong :( ) yet.

GB

[Yogy Namara]

Sounds wrong, you say? Wait till you hear my problem!

I need a USB cable where the male part is slightly longer. The reason I need this is because with my Cygolite lights, the female part is located somewhat deeper and partially blocked by the plastic mold of the lights themselves. A standard male can still connect and charge the lights, but they don't "click in" and will just fall off with the slightest bump.

It's possible that I can just shave off the base of a regular male part to make it longer, but I've yet to try this.

This is one of the reasons why I prefer the micro USB as used by Light & Motion (unfortunately their lights don't run while charging, but that's a different issue). Apparently one of the biggest flaws of the mini USB standard is that the locking mechanism is in the female part. Micro USB fixes this by moving it to the male part. In either case, the locking mechanism will eventually wear out and may need replacement, but it's much cheaper to replace the male (i.e. the cable) than the female (i.e. the device).

Yogy

[C. Duque]

Here is couple from dx.com that look like your first (not Ideal) example. For the price there is little to lose.

http://goo.gl/fdLseH

and 

http://goo.gl/h70cp0

On the 600k I do keep the power (USB) cable connected to my GPS with the help of a small rubber band wrapped around the "head" of the cable and then over the bike computer. That makes for a very secure connection without any additional hardware.

Carlos