BY ROB CARUSO
I recycled a VCR knob assembly and
turned it into a controller for the
Windows Media Player.
The knob assembly began its life as the control for a Sharp VCR. The VCR was given to me after it had stopped
working. I let my son dismantle the unit because he enjoys
opening things up and taking them apart. When the unit was
disassembled, I took particular notice of the knob assembly
— what it was comprised of, how it was assembled; I was
impressed by how much control was put into such a small unit.
In the center of the device were three buttons for
play/X2, stop/eject, and pause/still. Around the perimeter
was a spring return dial which when rotated clockwise
would fast forward and reverse when rotated counter-clockwise. It was refined to the point that a lot of thought
must have had to been put into its design, and I knew that
sooner or later it would end up in one of my projects.
The knob sat in the spare parts pile for awhile before
the idea came to me to use it as a media player controller
for my computer. While some keyboards have the media
player controls built into them, my trusty old IBM model
■ FIGURE 2. The assembled underside of the unit.
■ FIGURE 1. A close-up
of the VCR knob and the
doesn’t. (I still use this relic because I like the feel of the
beefy keys when I’m banging away at them.) I had been
meaning to do a USB based device and thought the
combination of the knob assembly and a PIC16C745
programmed as a media player controller would make
for a challenging and useful project. For those of you
who may not be aware, the 16C745 is a one time
programmable device with low speed USB built into it.
If I were to build the controller today, I would make use
of one of the full speed, Flash-based USB PIC controllers.
The play/X2 button became the play/pause button
while the stop/eject button became the previous track
button; the pause/still button became the next track
button. The forward/reverse dial became volume up and
down, respectively. I did not try to relabel the buttons
because the controls are so straightforward.
The hardware is simple and straightforward too
(see the schematic) — a group of switches wired to a PIC
programmed to send the required command codes to
control the Windows Media Player through a USB port.
The hardest part of the project was getting the device to
I made use of a microEngineering Labs (www.
melabs.com) PICPROTO 3 board on which to assemble
the project. The USB cable is available from HVW
Technologies ( www.hvwtech.com); (SKU 14120) and
features a series A USB plug at one end and a locking
connector at the other. When the knob assembly was