Garmin USB GPS or Antenna?

[Sirocco]

Hi Guys,

A friend at work bought an ex-police van recently and was trying to figure out what some of the cabling was etc. One of the devices on the roof was a Garmin product and she was kind enough to let me remove and have it.

Initially I thought it was an external antenna (GA-27) but the stripped wires look like they could be for a USB or serial connection. I have never seen an MCX connection but assume its similar to coax cable.

There are 8 thin wires (purple/grey/red/black/blue/white/green/yellow)

can anyone identify what I have?

Would like to get it working and not sure whether to try and solder a USB connection or if I am wasting my time.

any help appreciated.

Cheers,

G

 

[off-roader]

Garmin tech support has always been pretty good. Have you tried calling them to ask how to best wire it up?

 

[JRhetts]

From your photo of the case and wires, it looks like one of Garmin's GPS units without display. This might make sense of they had it piped into a multi-purpose display in the vehicle. Is there not a model number moulded into the plastic case?

 

[DaveInDenver]

FWIW, I have a Garmin 18x LVC puck that has 6 wires. I have no idea if it's relevant to the unit you have.

1 - yellow - 1PPS
2 - red - V+
3 - black - GND
4 - white - TXD
5 - black - GND
6 - green - RXD

I should edit to add the interface is RS-232 and expects 5V levels, so can be powered from a USB port.

 

[Sirocco]

From your photo of the case and wires, it looks like one of Garmin's GPS units without display. This might make sense of they had it piped into a multi-purpose display in the vehicle. Is there not a model number moulded into the plastic case?

Yes that is what I think it is. A GPS puck or mouse. No model numbers or other ID apart from the Garmin logo

FWIW, I have a Garmin 18x LVC puck that has 6 wires. I have no idea if it's relevant to the unit you have.

1 - yellow - 1PPS
2 - red - V+
3 - black - GND
4 - white - TXD
5 - black - GND
6 - green - RXD

I should edit to add the interface is RS-232 and expects 5V levels, so can be powered from a USB port.

thanks for that, maybe I should try and wire it to USB. Do you think if I matched the colour cables it would work?

Computer electrics are not my thing!

Thanks for your help guys.

G

 

[ReconH3]

It's definitely an antenna. My older Garmin III GPS had one just like it and it had a round plug with many pins. I don't have it anymore to take a look at it.

 

[Sirocco]

I did wonder if it was the GA27 external antenna as it looks identical. I just couldn't find a pic of one with bare wires. do you know what the 'round plug' was called? was it a garmin connection? or a standard MCX/BNC connector?

G

EDIT: Well I just searched everywhere and it is a GA26c that Recon used with his GPSIII. However it does use a BNC connector which uses coax cable, which mine does not have back to the drawing board.

 

[DaveInDenver]

I wouldn't expect if it was just an antenna that it would have that many wire or that type of cable. It should be impedance controlled at least, coax or shielded twisted pair maybe.

Not sure if my post was confusing, the 18x LVC is designed to be powered by 5V but is not directly USB compatible. You can use the host USB port to provide power for the puck and power a RS232-to-USB converter if it was low enough power, which is what Garmin does in their out-of-the-box USB pucks. Point is do NOT connect the puck to 12V!

Does it have four mounting holes on the bottom by chance? I wonder if it's a Garmin 35 receiver. Those have 8 wires.

Red = +5V
Black = GND
Gray = 1PPS
Yellow = Power Down (sleep mode input)
Blue = RX1
Green = RX2
White = TX1
Purple = TX2

 

[ReconH3]

It was similar to this but with more pins. I'm not sure if anyone else uses these plugs other than Garmin. I do remember that these were "special" Camel Trophy versions of the Garmin III. It only had the one plug, and everything came of the one wire. Power, antenna, and data cable for cloning. Just a thought: maybe that antenna had the differential gps sensor incorporated for more accuracy.

 

[Sirocco]

That looks more like it Dave.

The wires were confusing me.

found a manual here: http://www.manualslib.com/manual/253430/Garmin-Gps-35-Lp.html

I do however seem to be in over my head though!

Is this worth persisting with? I have a Garmin BT unit that I use with the laptop to run mapsource/N-Route and a handheld MAP60CX for backup running OSM. I was hoping to have it on USB so I could run it direct off the laptop if needed.

what do you think? can it be done? maybe a combination of USB (for data) and a cig lighter for power? or can the USB handle the 5v feed? the wires seem thin enough.

G

 

[DaveInDenver]

You wouldn't be able to power it directly from the cigarette lighter, but it would not be tough to hack up a regulator (Google LM7805). This puck is probably going to have a RS-232 NMEA0183-format protocol for an output, so you would have at minimum use a serial to USB adapter.

Easiest would be to build a custom cable with a 9-pin D-sub serial connector, 5V regulator and lighter plug. Then you'd plug the serial connector into an off the shelf USB adapter. Not the cleanest. I'd probably build a USB interface into a small box and use the USB 5V to power the puck, just completely eliminating the lighter plug option. You could get a commercial USB adapter and pull the guts out for your interface, for example. This would take a little soldering but nothing exotic.

Is it worth it, depends on how much you want to tinker. It's going to be more rugged and easier to mount externally but it's not necessarily going to be an more accurate or quicker than your other GPS receivers.