Convertible Automobile: Garmin Speaker/Charger Hack

MarkBooth · Occasional Visitor Joined: Jul 03, 2005 Posts: 10

I own two cars, a sedan and a convertible. In the sedan, hearing TomTom Navigator 5's commands through my Palm Zire 72's speaker isn't any problem (as long as I don't have the sedan's stereo turned up too loudly). In my convertible, on the other hand, hearing the voice commands can be quite a challenge. So, I found myself feeling jealous of all those Garmin iQue users that have that nice cigarette lighter accessory charger/speaker. This is the one I mean:

http://shop.garmin.com/accessory.jsp?sku=010%2D10407%2D00

Well, as it turns out, a good friend owned both the Bean Bag (friction) and the Windshield (suction cup) versions of the Garmin iQue mount. He wasn't going to be using the Bean Bag one anymore so he gave me the cradle/charger/speaker portion of it for a little hacker project.

For those not familiar, the above Garmin mount has cigarette lighter plug attached (via swivel joint) to an oval shape containing a speaker and small audio amp with volume control. That module is wired via a cable to the actual cradle where the iQue sits. In use, the voice prompts from the iQue are routed to the speaker in the cigarette lighter plug module and the car-powered amplifier in there does a great job of giving you a LOT more sound volume!

As it turns out, the Garmin mount device puts out exactly +5v DC when connected to the automobile's +12v cigarette lighter socket. +5v DC is EXACTLY what is needed by my Palm Zire 72 and, hopefully, by all other hand held devices of similar nature (please check our own device as needed). So, I spent a few hours hacking the Garmin charger/speaker to adapt it to my Palm Zire 72.

I cut off the cable at the CRADLE end of the Garmin mount. This left me with the charger/speaker with a length of cable attached. Inside the cable is four wires and a shield (Garmin calls the shield a "drain" wire). The four wires are color coded as follows:

Red: +5v DC
Black: Vehicle Ground
White: Audio +
Brown: Audio -

The shield ("drain") wire is not connected to any circuit at the cradle end of the original mount so I knew it did not need to be connected to anything on my Palm. Again... the SHIELD is NOT connected. It is NOT the audio negative, as is the case in some cables. The brown wire is the audio negative.

Knowing the above wiring schematic, it was a simple matter to fashion the cut end of the cable into a "Y" cable. Using solder and various sizes and lengths of heat shrink tubing, I fashioned a Y cable with the appropriate coaxial power plug (for my Zire 72) at one end and a 1/8" stereo plug (for the headphone jack on my Zire 72) at the other end. On my Zire 72, the Red wire goes to the coxial power plug's center tip, while the Black wire goes to the outside ground connection. Likewise, on the 1/8" stereo plug, the White wire goes to the tip (left channel) and the Brown wire goes to the ground connection.

Plugging it all together, the Garmin accessory charges my Zire 72 perfectly. And, on the Zire 72, setting TomTom Navigator's volume level to about 90%, leaving it there, and then adjusting the master volume at the Garmin's speaker is perfect. With the Garmin turned up all of the way, it is REALLY loud. Louder, I think, than the output from my friend's iQue with it set to maximum. It is EASILY heard above the wind and road noise, even on the highway in my convertible with the top down!

Obviously, other handheld device power connectors may or may not be as easily figured out or as easily obtainable. But if you've been craving that loud Garmin accessory speaker but didn't want to abandon your current handheld device, this may be your solution.

Have fun!

Mark

	PocketGPS
	Web