Instruction manual

LEDS1• 5
components. The user selects which filter the audio passes through by
pushing switch S1. After being filtered the audio signal arrives at U1:B where
it is amplified slightly by a factor of 22. After this, the amplified audio goes to
U2, an NE555 timer, that is configured as a retriggerable monostable
multivibrator. The circuit produces an output pulse every time the audio signal
gets above its threshold level. For example, consider a piece of music that
has a drum beat. The LEDS1 is set to low-pass the audio. The drum beat
makes it through the filter, is amplified by U1:B, and triggers U2. Now, you
might be thinking: “Isn’t sound a sine wave? Every time the audio reaches a
peak, it would trigger U2 and produce a flashing effect” This is true, and
sometimes a single drum hit will produce a couple of quick flashes instead of
just one flash, because one drum hit contains many peaks as shown in the
picture.
This is where some “tweaking” can come in to play, and is discussed later in
the manual. Now let’s take a look at the parts list and get building!