LED Meter Guide
The LED meter is a rare mod that is used by only the most daring (read: can
kill a parallel port) or well funded case modders. This mod uses the printer
port to transmit data to an array of 8 LED's, making them do whatever the
user can find or write a program for. From WinAmp sound movement to system
use, the possibilities are limitless. This guide will show you how to make
an affordable and safe meter so you to can have one of the most visually
entertaining mods ever made. The most common application of the LED
meter is for WinAmp. Using a visualization plug-in, music output can be
displayed on the meter in 2 different ways- Boom indication (vertical
meter), which indicates parts of the music rich in bass or when all the
instruments hit a beat at once, and Music illustration (horizontal meter),
which is the same effect as the equalizer visualization, only on your LED
meter in your case. The meter can also display various system usages from CPU
time to network usage to CPU temp.
For this mod, you will need:
8 LED's- Your choice in color and quantity of each. I recommend the use of 30mA
LED's and below. The forward voltage is 5V, so
<5V is also recommended. Use >30mA at your own risk, because if
it draws too much current, you will be out 1 parallel port. You will see
later that I used 2 each of blue, green, yellow, and red, in ascending
1 single sided printed circuit board- I chose the Radio
Shack IC board. It is perfectly suited for this mod, and if you have the
tools to split it in half, you can make 2 meters from 1 board (or on 1
1 DB25 male connector- can be any style (crimp-on,
solder-on, etc) you choose. Must be able to plug into your printer port.
Resistors for Each LED- You decide on the LED's, so you
determine the resistors. Since it's a 5V forward voltage, a 3.7v 20mA LED
would need a 68ohm resistor, 2.1V 30mA = 100ohm, 1.7V 20mA = 160ohm, etc.
Wire to connect between your board and plug- Can be
anything from speaker wire to a ribbon cable to CAT5 (which is what I used
And the usual solder, flux, etc.
You will first want to place your LED's along the board, taking full use of
the built-in ground bus, or making your own.
You will want your components on the plain or white side. Your anode (longer lead, positive) will go into the individual rows, while your cathode
(short lead, negative) will go into the ground bus. You will want your
colors to range from a blue/green spectrum to a yellow to red, or another
bright color to alert you to high levels.
LED's in place. Time to solder in the resistors. MAKE SURE YOU SOLDER
THE RIGHT RESISTORS TO THE RIGHT LED'S. Failure to do so will result
in wasted time and money (dead LED's).
160ohms is a hard to find (if existent) resistor, so I soldered a 150 and 10
in series. Notice how the board design goes so well with the mod.
Now your board is essentially done. Next we will move on to soldering into
the DB25 connector. This process is fairly simple. Make sure your solder
points are strong because this part will receive a bit of punishment if you
are switching between the meter and a printer, or if you want to unplug it
at night (like me). You should always have a hood for your connector too.
This will prevent stress on 1 particular solder point and will also prevent
NOTE: If you are using CAT5, be warned that it is extremely hard to strip
unless you have uber1337 wire stripping skills with your fingernails, a
knife, or some special order wire strippers. Also, you will need 1
additional wire for your ground.
On the DB25 connector, we will be working with pins 2-9 and 25. The bottom
channel will go on pin 2, the next on 3, etc up to 9. The ground will go on pin
25. See the diagram below for pin locations.
Now we need to prep our cable for soldering. When using CAT5, you can separate the pairs into pairs for your LED colors (assuming you used 4
colors). This worked great for me because I could use blue for blue, green
for green, orange for yellow, and brown for red.
I used the color-white for the lower LED of that color, and the solid for
the upper LED. Make sure you put your hood on BEFORE soldering.
Now flip the connector and solder your ground.