The operation is quite simple, the USB cable connects to a thumb drive inside the device. The thumb drive has been cracked open to expose the circuit board, USB power and the drive LED output has been tapped into. These 3 points are wired to a small circuit board, there is a circuit that stretches the drive pulses into an on or off signal that is buffered by a transistor to power the internal motor and LED lights. The pulse stretcher was needed since the USB drive would flash when it was being accessed. This would have caused the motor action to be very jerky and the internal lights would also have flashed.
The cost to purchase all the parts for this project should be between $10 and $15 depending on the deal you can get for the USB thumb drive and assuming that you have a few items in your parts junk box. Construction time should be 3 to 4 hours but it took me longer since I took a ton of pictures along the way and has some belt drive (or should I say rubber band drive) issues.
I am posting this project here since many of you may not have seen it on Hacked Gadgets.
Step 1: Gather the Parts You Need
- VHS Tape
- USB Cable
- DC Motor
- Thumb Drive
- 4 X Blue LEDs
- 4 X 68 ohm Current limiting resistors
- 3 X Diodes
- 1 X 220 ohm resistor
- 1 X 1000 uF capacitor
- small perf board
- hook up wire
- hot glue
- Rubber band
Step 2: Remove the Recycled DC Motor
To open your CD-ROM drive pop open the front using a paper clip and small screwdriver. This CD-ROM has 3 DC motors, one to spin the CD, one to open and close the drive door and one to move the read write head back and forth. Deconstruct the drive by looking for screws and plastic snaps. Look for a motor that will work well. The drive train that is used to open the drive tray is real nice in this mode. It has a narrow plastic section with all of the gears mounted in a row. A Dremel tool with a cutting wheel was used to slice the motor and gears right out of the CD-ROM drive.
Step 3: Prepare the VHS Tape
Take the VHS tape apart, there is usually 4 or 5 screws on the bottom of the tape. The top should just lift off after that. You will then be looking at two reels with what seems like miles of tape on them. I unraveled the small one by hand and it took forever. The larger reel was unraveled with the aid of a drill. :) I might have been able to just slip off the tape if I noticed that the clear portion of the reel was just locked in place with a simple turn. :(
Step 4: Open the Thumb Drive and Fine the LED Drive Circuit
You will need to crack the case of your USB thumb drive open. This Kingston drive was very easy to open. When one side was free the other side almost fell open. When the drive electronics are exposed you will have to hunt down the LED. In small devices like this it will be surface mount so it may be a bit hard to spot. Look for a clear device but if you still cant spot it just plug it in and locate it that way. Once you find the LED you will need to trace out where it is being controlled from. The traces are equally tiny, so you may want to use a magnifier loupe to make things easier. Have a look at the picture of my Fluke multimeter lead tip in beside the LED. It was hard to meter traces with it since the point seemed to be as fine as my thumb but eventually I got things traced out. Turns out that the R3 is the current limiting resistor for the LED.
Step 5: Wire Up the Thumb Drive
You will need to solder wires to the USB positive and negative connections. Have a look at this USB pinout page for information or just meter the outside pins to determine the polarity. Some helping hands will make soldering the connection easier. I would recommend using some helping hands that have a magnifier built into them. The third connection that you need to solder to is the LED output that was identified in the last step. One word of caution here, I soldered to the surface mount resistor to access the signal and it worked fine but broke off a few minutes later. Even though the gauge of the wire was small it had enough leverage to pull the solder and pad from the surface mount device. I had to scrape the solder mask from the trace and solder to that. Once I confirmed that it was working I poured hot glue over the entire device to make sure there was no more strain on any of the connections.
Step 6: Construct the Control Circuit
The control circuit is very simple for this device, the number of diodes that are shown may need to be adjusted. The output from the Drive LED output didnt go to zero so the diodes are there to drop some of the excess voltage so that the circuit does not turn on until the drive output actually turns on. The 1000 uF cap is there to smooth the flashing drive LED output. Without the cap the circuit would still work but the LEDs and the motor would be pulsed. I tested the circuit concept on a breadboard first to make sure it worked before making a permanent perf board version. The component locations were made to be very compact since there is limited room in the case (if you want everything to remain hidden).
Step 7: Mount Everything in the Tape Shell
I used the Dremel to carve out a bunch of plastic ribs and spacers from inside the tape shell. It was still very tight to make everything fit and not be seen through the windows but it did fit. The circuit board was also slathered with hot glue to hold everything in place. I would not want one of the wires to pop off after the circuit board was hot glued in place. I didnt use any heatshrink on the LED or motor wires, instead some hot glue holds things in place and also provides short circuit insulation. A rubber band was used to turn one of the tape reels, I had lots of trouble with this since the slightest tightness on the rubber band would cause the reel to pull in against the reel guides and stop turning. It was smooth to turn by hand but the belt was working against itself. If I used a tighter belt to prevent slipping it would obvously oull the reel harder against the guides and still cause binding. The solution was to take one of the metal tape roller guides that was in the tape shell and use it to push the reel away from the guide and keep it spinning freely. The roller guide was just slipped over a bent paper clip that was hot glued in place. By this time I was thinking that I sould get a hot glue company to sponsor the build. :)
Step 8: Finished Device
All that is needed now is to screw the top back onto the device and give it a try. If the metal presser pads put too much pressure on the spinning reel you may have to remove it. It worked without removing it, but it spun much better after the presser was removed.