HowTo: Turning a cradle into a car kit

HowTo: Turning a cradle into a car kit

Published by SwampNut
01-30-2003

HowTo: Turning a cradle into a car kit

I got my car kit done a few weeks ago, but still haven't found the time to put together an article on it. Here are the photos I took, though, feel free to ask questions if you like.

This project is not trivial and took a lot of time. It could be easier if you're willing to settle for more simplicity, like only getting sound out. I wanted to have sound, serial, power, the works. It requires the ability to solder small connectors and skill with a Dremel (high speed rotary tool). Basically I took one of the charging adapters apart to get the connector, and duplicated the mounting plate for it inside the cradle using a CD-ROM case cover. Some of the fitment is pretty tight, so you have to have a steady hand with the Dremel. The mount you see on the rear of the cradle is a leftover from a Nokia kit I believe. It is a standard car cell mount which can be purchased in many forms from many sources. There are also flexible pole mounts and others available.

The end result is that I can drop the XDA into the cradle in the car and it is charged, the Pharos GPS is connected (via the PS/2 connector you see), and stereo output is provided via the three-conductor jack on the back of the cradle. I am using the built-in microphone, after some experimentation with other options. It appears the XDA needs a high level microphone input, a straight microphone does not work. This sounds fine to most callers, but it means that I can't put the device into "car" mode which means you also get sound from the speaker on the device.

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#1 (permalink)

By Convergent on 02-02-2003, 10:43 PM

Way Cool!

This is really awesome! Could you provide a wiring diagram and list of what parts you used. I also use a Pharos GPS, and I'd love to build this connector. I don't think I'm going to do it the same as you, because I use the mount that you see in the other article here.... the home-made portable mount. This will probably work the same with a cable instead of the cradle, I'm assuming. I'd just like to crack open the Pharos Y-Cable and add the audio pins... It would be the ultimate cable... power, serial, and audio.

I also ftp'd the images to pdaPhoneHome so they aren't hot linked any longer. Thanks for providing this!

#2 (permalink)

By SwampNut on 02-03-2003, 12:34 AM

The parts list will make you laugh... In photos 1, 3, and 4 you see how I'm take a CD-ROM case cover to turn it into the mount for the connector. The edge, as you see in the photo, is perfect to "notch" into the little tabs on the bottom plate of the cradle. Notice that the stock PCB has holes to catch on little pins on those tabs; the rolled edge of the CD case is perfect to catch on this also. Same thickness. The connector from the AC adapter is thicker than the stock connector, so I had to cut out that piece and use another to hold the connector in place; alignment is perfect using that method. It was glued to the other piece with Duco.

In photo 2 you see the "ears" that I peeled back from the connector; these used to be the locking tabs. Later they will become the method to attach the connector to the plastic. In photos 5/6/7 you can see how I used large-head screws and nuts with washers to attach those tabs to the plastic. I made the tabs into a loop and measured their position, bent them as needed, then once the connector fit in the cradle just right, put on the screws. The connector is VERY solidy fixed this way, surprisingly.

Other parts... Standard stereo 3.5mm plug from an electronics supply house. The PS/2 style connector for the serial feed from the Pharos GPS was just cut off from an old keyboard that no longer works. (Thus justifying why I have had a dead keyboard in my closet for two years...) The power supply connection is the stock connector from the cradle originally. You also see a 2.5mm connector in one photo; that was going to be for the microphone, but I discovered it would require additional electronics. Therefore I didn't use it, and I leave the phone in regular (not car) mode, using the built-in microphone. It's not perfect but very good. People say I sound a bit distant but 100% intelligible.

The mount is something I had in my "cell phone stuff" parts box. After 15 years of using a wide variety of phones/mounts/kits, I have a lot of spares and extras. I'm 90% sure this came from a Nokia 82xx series car kit, or possibly a 61/51xx kit. In any case, mounts use a standardized bolt format like this, and you can buy MANY different types of mounts at cellular dealers. I have one on my desk (where I mounted by other cradle which I modified to allow use of the headset while cradled) which is a flexible any-position gooseneck type. The little metal plate affixing the mount is something I cut from flat aluminum; it's actually a prototype of the mount that I used to mount my last cell phone onto my motorcycle's clutch master cylinder (the PPC-PE mount for the bike is next). It's just to back up the plastic for strength, and since it was already cut for the size/bolt patter of a cell mount, it was easy. It prevents the use of an auxilliary battery on the PPC, so if that's a concern, you'd have to use an alternate method. Also, attaching the mount to the bottom of the unit is perfectly viable. In my case, I chose not to because this afforded a better position in my car.

So as far as the electrical connections... Very basic. You can see a pinout of the XDA connector here: http://www.mywirelessoffice.com/xda/connector/

The Pharos cable pinout is here, and was provided by someone else on PPC Thoughts: http://www.mywirelessoffice.com/pharos/pinout.html

Tools list:
Fine-point 25w soldering iron with a good, clean tip
Very thin solder, rosin core
Small cutters and needle nose
Dremel, cut-off wheel, and round shaping tool bit
Voltmeter helps if you have any issues/doubts
Screwdrivers and pliers