FINAL YEAR PROJECT
PROGRESS REPORT
BY Damien Higgins
B.E. ELECTRONIC ENGINEERING
An acoustic-triggered, battery-powered LED chaser for
portable music players.
Supervisor: Dr. Peter Corcoran
Table of Contents
Table of Contents
1. Introduction
1.1 - History
1.2 - Applications
1.3 - Project Abstract
2. Proposals for tackling project
2.1 - Sensor stage
2.2 - Audio input amplifier stage
2.3 - Processing the signal stage
2.4 - LED driver stage
2.5 - Power subsystem stage
2.6 - Final stage
3. Progress to date
3.1 - Research
3.2 - Sensor stage
3.3 - Audio input amplifier stage
3.4 - Processing the signal stage
4. Task list and Project plan
4.1 - January
4.2 - February
4.3 - March
5. Conclusion
6. References
1. Introduction
History
Light chaser circuits have been around for about 100 years. Since they used
expensive noisy motor driven mechanical switches to flash the lights, the first
ones were mainly limited to commercial ventures that could afford them, just
like the ones that first appeared on Times Square. By the 1970s, integrated
circuits and transistors eliminated the need for mechanical switches and
dramatically reduced the cost of light chaser circuits so any hobbyist could build
them. LED’s or light emitting diodes which became available around the 1970s
also reduced the power requirements of these circuits.
Applications
Today, light chaser circuits have a wide variety of uses. Christmas lights being
one of the many examples. Since they usually grab people’s attention, they are
often used to help sell products or to highlight a retailers product to make it
stand at from the crowd. Led chaser circuits are also used in VU meter’s by disc
jockey’s to create an atmosphere. The led’s can light up at different times and in
different patterns depending on the volume or frequency of the music.
Project Abstract
The goal of my project is to build a set of analog processing modules to capture
an audio signal and by analyzing this signal to drive a series of multi-colored,
high power LED lights. The design will be used as a portable light chaser and
could be productized as a peripheral for a portable music player.
2. Proposals for tackling project
The easiest way to complete this project successfully is to break it down into
different stages. By taking each stage one step at a time, the project is easier to
complete.
Sensor stage
Firstly some audio will need to be detected to have something to work with.
This could be done with some sort of sensor like a microphone for example.
Extensive tests will have to be carried out to determine which sensor will be the
most valuable for the purpose that we intend to use it for. Tests for sensitivity
and bandwidth should be carried out to determine which sensor to use for my
final design.
Audio input amplifier stage
The signal got from the sensor will then needed to be amplified somehow. To
achieve this, extensive research and tests should be carried out to determine
what sort of amplifier will be used.
Processing the signal stage
The signal obtained from audio input and sensor stage will then need to be
processed by a set of filters. This is done to provide some sort of information
about the signal or the frequency spectrum coming into the system. This should
be achieved by researching, analyzing, constructing and testing various filters.
Based on these tests, a final design needs to be selected.
LED driver stage
The unit should drive multiple banks of LEDs. It could be desirable to use the
information from the signal processing circuitry to modify the output pattern of
the LEDs to flash to different frequencies at different times.
Power subsystem stage
After all the stages are completed, the system needs to have an efficient power
supply using battery power.
Final stage
At this stage all the modules should be brought together into a single integrated
design. It should also be at this stage that any modifications take place.
3. Progress to date
Research
To start off I researched different light chaser circuits around and looked
through different ways of approaching and design the system. I also read
through different projects using LEDs including one where LEDs were used
within a VU meter.
Sensor stage
For the sensor stage, extensive researched on a number of audio sensors to try
and decide which would be best for use in the system was carried out. After
thoroughly looking at different sensors, I chose 5 different electret microphones
to test. I constructed circuits to power and test each microphone individually.
After evaluating each microphone’s sensitivity and bandwidth results on the
oscilloscope, I chose one for the final design.
Audio input amplifier stage
For the amplifier stage of the circuit, I reviewed a number of different
amplifiers and constructed a number of these. After testing and evaluating each
amplifier and observing the results with the oscilloscope, an amplifier design
was chosen.
Processing the signal stage
Next I looked into processing the signal using a set of analog filters. I tested a
number of different filters including a low pass filter, a high pass filter and a
band pass filter. Assuming the frequencies we want are between 20 and 20,000
hertz (typical for modern music), we should aim to work with these.
4. Task list and Project plan
January
 By the end of January I hope to have completed most of the LED driver
stage and have some sort of working module completed.
February
 For the month of February I plan to work on the Power subsystem stage.
March
 In March I plan to tie up all loose ends with the project and complete the
Final stage.
Conclusion
Overall a big effort is required to complete this project but when everything is
completed it will prove to be worthwhile.
References
www.wikipedia.org
http://www.allaboutcircuits.com
http://www.sensorsmag.com/sensors/electric-magnetic/anintroduction-analog-filters-1023
http://wild-bohemian.com/electronics
http://www.reconnsworld.com/audio_electretamp.html
http://electronicdesign.com/article/electronicprojects/disco_vu_lights.
aspx