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Jun 02, 2006, 07:18 PM
Professor of Wood
kd7ost's Avatar
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Mini-HowTo

Garmin geko mod for flight


This "How To" is being located in a public forum for ease of access.

This mod thread applies to the Garmin geko 201. You’ll need to use a Torx T-6 bit to remove the 6 small screws in the back. Caution, this mod will violate any warantee. Proceed at your own risk.

Dan

The first picture shows the back off and the internal battery identified as well as a few other items. This little internal battery is only held in place with two tiny leads soldered to the board. You can barely see these leads on the left side of the battery under the hot glue in my picture. Yours will not have hot glue in place when you open up the unit. I recommend gluing the battery down to the board with hot glue to keep the vibration strain off of those two little leads if you're using an internal combustion engine. The glue application I placed here has held up nicely in a gasoline powered plane with a single cylinder for many hours of use and spanning two years. Having it vibrate loose and shut down the GPS is what prompted me to develop the mod. If I had been relying on the GPS at that time, I would have been going home without the plane intact.
Last edited by kd7ost; Jun 02, 2006 at 07:34 PM.
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Jun 02, 2006, 07:20 PM
Professor of Wood
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This next one shows where the OEM connector would mate to from the inside. It's an expensive connector and keeping it in place could be the hardest part of the UAV to GPS task. I modified this geko to have a less expensive yet highly reliable RC connector installed. Note where you need to connect to. The "RS232 in" is not likely needed and I don't employ it. The hole location for the grommet is important. You need to stay on the side away from the foil covered RF section so when you put the two halves back together there is adequate clearance. This will prevent puncturing the RF shield foil cover.
Jun 02, 2006, 07:29 PM
Professor of Wood
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This shows the final job. Although this was done initially with a standard black Futaba connector, I later installed a yellow futaba connector. I keep all my GPS connections on yellow connectors. In this set up you may connect +3.3 vdc to the red wire and return 3.3 vdc to the black. You need to connect the white wire, RS232 (NMEA or whatever you use) to your guildance, GPS overlay etc. The return side of any other unit, Overlay, guidance devices etc need to be connected to the black wire as well. They need to share a common ground.

A severe word of caution. That connector should not match your RC system, or you need to really stay on top of it. Putting that connector accidentally into a receiver port will put 4.8 to 6 volts or higher into your geko. If you turn on the geko with that voltage attached, you will fry it. Note that I use the male end so it can't plug into the receiver. Feel free to select a different style of connector. Make sure to strain relieve the wires inside with a dab of hot glue or whatever so it won't get tugged through the grommet.

If you leave the red wire disconnected, this won't be an issue. But, you need to operate off of internal AAA batteries and they go dead fast. I find that putting in an aux power source at 3 to 3.3 vdc into the red wire makes the unit extremely reliable. With AAA batteries inside being used the geko drains the cells too fast. Also, the built in AAA battery pack makes contact through those two tabs identified in the first picture. They contact the two etched PCB pads shown. If the little screws on the side aren't tight enough, vibration will cause the geko to shut off. You might even have to bend them up just a tad to make good contact but that could fatigue the brass tabs. It's best to use an outside power source with gas engines and the vibration they produce.
Jun 02, 2006, 07:32 PM
Professor of Wood
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This shows after it's been put back together. Put the screws in fairly tight but don't bulge out the rubber seals on the sides. That holds the battery box to the circuit board. Place some AAA batteries in the unit and turn it on. Rap on the sides of the geko a few times from either side. If the unit shuts off when you tap it, the screws around the center need to be tighter or those tabs on the battery holder part of the case aren't contacting the circuit board real well. Again, I can't emphasise enough that a 3.3 volt input on the red and black wire in the RC connector will resolve that if you have the space on your plane for it.

Dan
Last edited by kd7ost; Jun 04, 2006 at 12:07 AM.
Jul 27, 2006, 12:02 PM
JettPilot's Avatar
That is a really helpful bit of information Dan, thanks for taking the time to share it with us I will modify my Gecko 201 as per your insturctions before it fails, but I do have a couple questions.

I do not have hot glue, do you think that GOOP would hurt the circuit board or eat away at the solder connections if I use that glue instead ?

Where do you get the rubber grommet for where the servo wire goes out ?

JettPilot
Jul 27, 2006, 12:18 PM
Professor of Wood
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Quote:
Originally Posted by JettPilot
I do not have hot glue, do you think that GOOP would hurt the circuit board or eat away at the solder connections if I use that glue instead ?JettPilot
I don't know that one. I've never used goop and don't know what the base is. It's pretty smelly as I recall and may contain some form of MEK or Toluene. I would avoid it on a PC board. The hot glue can be had for dirt cheap. I use it in these strain relief type projects because it bonds by melting and cooling, not by chemical bonding. It's also fairly easy to pick it loose if you want to remove it. I may be wrong about the goop. I just don't know.

Quote:
Originally Posted by JettPilot
Where do you get the rubber grommet for where the servo wire goes out ?

JettPilot
I got them from an electronics supply or surplus store. I have bins of stuff like that. Radio Shack sells an assorted package of vinyl grommets that will do nicely too.

Dan
Oct 21, 2006, 09:12 AM
JettPilot's Avatar
I finally did the mods and flew it, they work great The RC connector will be much more reliable and smaller than the garmin cable I was using. I used a bit of 5 minute epoxy on the battery, just enough that it would not be hard to get the battery off if I ever need to.

JettPilot


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