I thought about trying to fit my retractable Cruzer drive, but upon further inspection, decided that it would be a huge challenge, plus I wanted to keep it original looking when closed. I happen to have a male - male USB cable that a friend gave me. This is why I went with the female USB connector here.
For this Instructable, I have already knocked out the laser side-cut key that went to my friend's new Beetle. I used a the key for my 1991 VW Golf and trimmed it to fit in this Flipkey.
Additionally, I was at a big box retailer and found a Kingston 4GB Micro SD w/ USB adapter. The USB was normally $25 - Marked down to $14.90. Add to that a $10 mail-in rebate - this whole project cost on the order of $5.00.
If you have to purchase the Flipkey or a USB, your costs will vary.
On with the Instructable.
Step 1: Getting the Pieces Together
Micro SD card with USB adapter - I used a Kingston MBLY/4GBKR
A male USB connector
A female USB connector
4 wires or 4-wire ribbon cable
Dremel tool - Very handy!
Low-Temp soldering iron and solder
Baking soda - Trust me on this!
Step 2: Getting Started
Use a pulling and bending motion to separate the two parts of the key.
Set the key half aside and open the electronics part. It is snap fitted together. The easiest way to get it apart is by using your two index fingers to pry it open where the tip of the key would rest when closed.
Once open, remove the electronics, battery, and battery clip.
Notice the tactile switches on the circuit board.... keepers?
Lift off the red rubber panic button and set it aside.
Step 3: Dremel Your Way to Happiness
Look at the USB adapter, it has a raised lid on one side. Dremel into the bottom half of the housing some to make room for this. Visualize the thing together and you can imagine where to remove material to make it fit.
Carefully measure and remove material where the Panic button was. This is where you will install a female USB connector. Go slow so you don't make the opening too big.
Frequently test fit your female USB in the opening to make sure you get a good fit.
On the top half of the housing, push the alarm buttons in as much as possible and trim off the 3 inside portions that protrude into the housing. These contacted the tactile switches originally. This will keep the buttons from interfering with the innards later. Trimming these tabs will not affect how the buttons feel from the outside.
Step 4: Fixin' Up the Micro SD
Mate the Micro SD housing to a male USB. I took the male USB apart, only keeping the white inside part. Connect it to the Micro SD adapter housing and test the fit in the key housing.
Step 5: Need a Little More Room...
I peered down the inside as I held the two housings together. I noticed that if I trimmed the female USB housing down, it was going to fit.
I took the Dremel tool and cut off just the top portion of the housing. Then I sanded down the white plastic portion a bit to make the fit.
Step 6: Solder Up the USB's
When you lay this out, make sure you always flip one piece over the other. Don't twist.
This is difficult to describe. Worst case scenario is that your computer will not recognize the drive and you will have to resolder after reversing your wiring.
After soldering, slip the stripped male USB through the USB opening first, followed by the female USB in its final place.
Glue the female USB in place using the good ol' baking soda trick. Glue both sides and get some underneath it. Cover liberally with baking soda and pack it in with a small screwdriver. Dump and blow off the excess baking soda.
Step 7: Making the Fit
*I decided against it, but you could remove the plastic cover from the micro SD adapter by cutting or sanding. I wanted to keep this intact in case I ever wanted to do something else with the adapter.
A little more work on the bottom of the housing or the female USB will make the fit.
If you see daylight through the bottom of the housing - you went too far!
Step 8: FINAL ASSEMBLY, (Then Show N' Tell!)
Next, replace the red panic button over the USB opening to serve as a dust cover.
Mine took a small amount of trimming to compensate for the metal of the USB sticking up around the edges of the opening.
I thought I'd try placing the panic dust cover under the closed key for safe keeping while the USB was in use and replacing it to cover the USB when not in use.