Trying It Out
Okay, you’ve been taking it on faith that this is
going to be a cool project, and we appreciate it. But now it’s time to
get the thing going and see whether you think it’s as much fun as we do.
You can use any music you like
to get the effect going, but we found that music with lots of
instruments — like a swing band with lots of brass — works best. Also,
music with an upbeat tempo moves along and gets the lights switching on
and off faster, which makes the effect better. Our favorite number for
dance to the music? Ella Fitzgerald singing
Take the A
Train,
by Billy Strayhorn. (Ask your parents; they might
have heard of it.)
Here are the simple steps to get this project going:
1. Pop the batteries into the battery pack.
2. Flip the on/off switch to on.
3. Put on some music.
That’s it! Watch the lights go on an off in response
to the high and low frequencies in the music. You can adjust the
sensitivity of the LEDs by turning the potentiometers. Here are the
obvious things to check out if you’re having a problem:
Check that all the batteries are fresh and tight in the battery
pack and that all face the right direction.
If one or two LEDs aren’t working, replace them.
If two LEDs in series with each other aren’t functioning, you
might have reversed the long and short leads of the LEDs; if so, just
replace that pair of LEDs.
You are playing
Brahm’s
Lullaby. Brahm’s Lullaby
will not light up
a single LED. Switch to Snoop Doggy Dogg or Motörhead.
Taking It Further
By now, you’re probably jumping and jiving to this
cool light show, playing every CD you have to see what they do, and
still, you want more? Here are a few different ways to take this project
further: Obviously, you can change from a
musical staff and notes to any kind of shape you might want to define
with your LEDs. You can have two stars or a sun and moon, for example.
You can use a
band pass filter
to add more layers of
frequency. For example, between your high pass filter and low pass
filter, you could add two more band pass filters to hit intermediate
frequencies and have four sets of LEDs going off in response to music.
You could miniaturize your circuit so you can pin
it on your shirt or take it with you to parties. A few steps would help
you to get a smaller circuit. First, you could use smaller LEDs. (This
project uses T-1 3⁄4 LEDs, but you could use T1 LEDs.) You could also
use a different method of building the circuit called a
dead bug
circuit.
Imagine an IC turned on its back with its little
prongs sticking up on the air, and you get an idea of what we mean. This
method doesn’t involve a breadboard but makes connection directly to the
LED. Check out
www.arrl.org
(American Radio Relay
League online) for some ideas about using the dead bug approach to
building circuits.