Ramsey Electronics LEDS1, Quick Reference Page Manual

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LEDS1
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WARNING: According to the Epilepsy Foundation it is
possible that this kit may present a risk to those with this
affliction. Affected individuals must be aware of the
possible triggering of seizures by certain visual stimuli.
INTRODUCTION
Everyone has seen a strobe light at one time or another. The bright
eye-popping lights are real attention-getters. They typically use Xenon bulbs
which require high-voltage. In recent years, super bright LEDs have become
cheaper and brighter, to the point where they rival flashlight bulbs. Now,
using some of these LEDs, we bring you the LEDS1! The LEDs take the
place of a Xenon flash bulb. You get a nice bright
blue flash without high
voltage, and no glass tube to break. Included with your kit is a 9 LED array,
but a 20 LED array is also available from Ramsey. In addition, the LEDs will
last virtually forever instead of burning out after a short time like a tube. As
well as flashing at an adjustable rate like traditional strobe lights, the LEDS1
also has an audio input that allows it to flash to music. Both high and low
pass filters allow the LEDS1 to flash to treble or bass. And for even more
expandability, there is an external trigger jack that allows you to control the
LEDS1 with your own external source or connect two LEDS1’s together.
LEDS1 CIRCUIT DESCRIPTION
Before we begin dissecting the circuit, let’s have a look at the “big
picture” and see what it is that we’re trying to accomplish. What we want is to
have a circuit that will flash a bunch of super bright LEDs at an adjustable
frequency, and also be able to flash them in response to an audio input.
The adjustable frequency is generated by U3, LM555 timer IC. The
potentiometer R19 controls the frequency at which U3 oscillates. The pulses
from U3 are fed to Q1, a power MOSFET. This MOSFET switches all the
LEDs on whatever LED board is plugged in to jack J5. A power MOSFET is
used because it makes a good high-current switch and won’t get hot. That’s
right, the LEDs are drawing enough power that heat is a design concern!
To make the LEDS1 flash to music is a bit more complicated. The
first step is to run the audio through a filter depending on whether you want
the LEDS1 to flash to bass or treble. There are two user selectable filters to
do this: high pass and low pass. The high pass filter will filter out low
frequency signals and allow high frequency signals (treble) to get through.
The low-pass filter attenuates high frequencies and lets low frequencies
(bass) through. The high-pass filter is made up of U1:A and its support
components. The low pass filter is made up of U1:C and its support