I-36 GPS to Computer Connection

This is a project I've been meaning to do for the better part of three years and finally got around to doing it. Having my Garmin GPS easily visible at the helm is almost a necessity. Connecting it to my IBM computer so I can visualize location, waypoints and routes is also very handy. I use either Nobeltec or FUGAWI navigation software. Providing power to both the GPS and the computer saves batteries and allows you indefinite use of both the GPS and computer. And finally, it's a lot faster to set up waypoints and routes on the computer and upload them to the GPS rather than try to enter them letter by letter on your Garmin!

I had bought, early on, the $25 "Garmin power & data cable" at West Marine. With about 6 feet of cable from the 12 volt cigarette lighter plug to the GPS and another 12 feet to the serial connector for the computer, there was some flexibility in locating the two so they could be connected. However, tripping over wires, and securing the computer in a seaway were constant challenges.

My desire was to have a cable connection at the binnacle to power the GPS and send data down below to the nav station. I wanted a second power/data connection at the nav station so I could keep the GPS below and still have it connected to the computer. Finally, I wanted a secure place for the computer where the data cable could be attached - and that it be long enough to allow taking the computer to the table for ease of use when conditions permit. Having power available for the computer was also necessary.

Prowling the net, I found the key to the project at Larry's pPlug web site:
http://pfranc.com/projects/g45contr/g45_idx.htm.
To design your own system, this is the one single part you can't get anywhere else - the plug into the back of the Garmin. The web site even gives you a great assembly diagram:
http://pfranc.com/projects/g45contr/assemb.htm You can order as many pPlugs as you need, and pay what you think is right - yep! If you don't want to go through the hassle of making up your own cables, they'll do it for you (at a price).

(Over four years of enjoying this rig, I encountered two corrosion problems in the plug, here are pictures of the problem and a possible solution. It also shows pictures of the soldering steps. pPlug pictures. 3/21/07)

The three components to be made included the GPS mount at the binnacle, a power & terminal block, and a drawer/shelf for the computer. The plastic parts came from Tap plastics; wire, serial connector, terminal block and wire-tie anchors from Radio Shack; 14" full extension drawer rails from Home Depot; 2 12-volt cigarette sockets from Kragen Auto Parts; and 1x3 lumber from the workshop. Total parts cost around $100.

The folks at Tap Plastics were most helpful is teaching me how to bend the acrylic plastic. Using a heat gun (used for stripping paint) worked just fine. I built a simple jig on a 2x4 with a 1x4 block and a 1" dowel to make the bends that would slide over and squeeze tight on the binnacle rail. Gentle heating for 3-5 minutes was enough to soften the plastic and make easy bends. Spraying with water helped cool it quickly so it would stay in place. I took the heat gun along to the boat when I fitted it to adjust the grip.

The power block/terminal is the junction point for the two power/data cables, the 12 volt power from the panel, and the data cable to the computer. I used a 50' roll of 24 guage telephone wire - the stranded, flexible type, and set it up with black as ground, red as hot, green as data out and yellow as data in. It was simple, in theory, to make the connections on the little 4 position terminal block, but tedious with big fingers after the sockets had already been wired!

The computer drawer is 1" wider and longer than my computer - about 10" by 12" - and 2" deep. Again, the Tap folks were very helpful in suggesting gluing sequences, but it went quite easily. The rails are screwed to the 1x3, and 3 holes were deep-drilled to screw the 1x3 to the shelf. The rails are drilled and tapped with 8 x 32 x 3/8 bolts to attach the box. The white plastic was added after the basic box was screwed down. There is a 5/32 hole drilled from the outside through the 1x3 which allows for a long 1/8 stainless cotter pin to hold the drawer in the open or closed positions. The pictures below should be self explanatory.

We've given it an acid test with the cruise to Petaluma, complete with pounding out of Emoryville with plenty of water flying around, and redoing a bunch of waypoints sitting at he table going up the river.

If you have any questions, send them along to Rick Van Mell. 5/28/03

Heating plastic	Bending plastic	Cooling bend	Bending jig.
Installed	Helmsman's view	Set for side view	Optional angles
GPS mount	Stowed GPS holder	Power block	Power block detail
Work in Process	My helper!	too dark	Computer connected
Computer connected	GPS in Place	too bright	Empty Drawer
Power Block	Nav Station	GPS at nav station	pPlug!
The critical pPlug!	Connected at table	Connected at table	Ready to go.