PHOTO 2. Color organ
controller board. The μC
target board is on the left
side of the board. Power
supplies are built across
perf board in the proper
positions so that the
target board could be
slid on and soldered. The
wire wrap pins not only
provide the electrical connections but also provide
the physical support for
the target board.
I packaged the color organ in a
triangular box I purchased. The box
seemed about the right size for the 40
LEDs I was going to use for the display. I
replaced the glass front that came on the
box with diffusion plastic from the hardware store. The plastic I used causes the
LEDs to appear like fuzzy circles of color
about 1-1/4 inch in diameter. The back
panel of the box has convenient swivel
tabs that lock into slots on the box which
make taking the color organ apart and
putting it back together very easy.
The LED leads were bent around
toward the LED and glued directly to
the box’s rear panel. I laid out the LEDs
in geometric patterns, but you can lay
them out anyway you want. Wire-wrap
wire was used to connect the LEDs
together and to the output board.
The color organ’s control panel
was built from a piece of sheet metal.
The control panel has the line input
jax, a condenser microphone, the
mic/line switch, and the power switch.
I decided to hard-wire the power supply to the unit, so I drilled a hole in the
back panel and ran the power supply
wire through it. I then tied a knot in
the wire inside the box for strain relief.
Once your color organ is assembled, do the following:
supply conflict between the color
organ and the USB development hardware. Removing this resistor means the
target board will always be powered
by the color organ’s power supply.
1) Plug in the wall wart and turn on
the power switch to check the power
supplies. You should have 3. 3 VDC, 5
VDC, and a high voltage output
between 8 and 12 VDC. If there is a
problem with a power supply, find and
fix it before continuing. Check for
power and ground at each socket
before installing the ICs.
2) Program the μC with the provided
2) There is an LED on the target board
which will be on while the color organ
is operational. The LED can be
removed if this is a problem.
Build the color organ using the
schematics and parts list as your
guides. I used wire wrap, but you can
build it anyway you choose. I built the
main controller portion of the color
organ on one pref board and the output section on another, but they could
have been built on a single board.
Six connections are required
between the target board and the
color organ. Since the I/O pin holes on
the target board are on .1” centers (the
same as the perf board I was using), I
pushed wire wrap pins through the
3) With the μC programmed, you
should see the LED on the target
board light up (assuming you haven’t
removed it yet). It should come on
with the power and stay on indicating
the display processor is running.
4) Perform an initial calibration of the
microphone preamp’s gain. This can
be done by connecting a headphone
through a capacitor ( 10 μF will do) to
the preamp output and adjusting the
trimmer for no distortion. After your
color organ is working correctly, you
may need to back down the preamp’s
gain so the color organ’s display is not
completely saturated when the mic
source is selected.
PHOTO 3. The color organ is built onto the rear
panel of the display box. The wire out of the bottom
is connected to the wall wart power supply. The
output board is on the left, the control panel is in
the middle, and the controller board is on the right.
PHOTO 4. Rear view of the color organ. Black spot on the top
left of the control panel is the condenser microphone. Below it
is the line input jax. Next is the mic/line switch and furthest to the
right is the power off/on switch. You can see the swivel tabs that
lock the back panel into place.