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This is my version of the LED boxs that i have seen on this site. This formed the final part of my degree course as a trainee Secondary Design Technology Teacher.

Its pretty simple. I took the flashing circuit for an led box and built it into a ready made 2.1 system, then made a new housing for it.

Have a look here for a video of the finished product:http://youtu.be/0kvhXYVkGGU

Credit to motadacruz for his instructable as it was his awesome guide that got me doing this one, anyway have a look at this for the circuit but forget about the stereo cable as we are going to hard wire this into our audio circuit
https://www.instructables.com/image/FMZXXB8G5W7R47J

The Circuit to control the LEDs consists of a NPN transistor (everyone recommends tip31 but i used tip 121 as thats what we had in the electronics cupboard). The base (left leg) connects to the signal source i.e the positive wire on the speaker. The collector (middle leg) connects to the first negative leg in the chain of LEDs (the amount of LEDs you can run depends on your voltage) the emitter connects to the 0v rail on your power supply. Thats it. there is no need to ground the negative audio signal like everyone else states.




Step 1: Getting the circuit and testing

So this is the build:

I chose a cheap 2.1 system, stripped it down and played with the circuit. Although this system was AC (i live in the UK) it had transformer and bridge rectifier to lower the voltage and produce DC current. A fiddle with the multimeter showed it produced 17V

Sand down the rails to expose the copper before drilling holes to run your power leads from (i drilled 3 holes so i could have lights on the left, right and bass)

once you have run a power supply off the amplifier board and created your circuit you should get something like this:
http://youtu.be/h99rDZ19_vs 

(i have these LEDs in series and paralel in order to test but basically they are superbright Blue LEDs, they have a safe working voltagge of upto 5.5v       17/5.5 = 3.09 so i can have 3 LEDs in series and a protector resistor.

Now plan out how you want the lights and it will determine the design of your housing.
I  went for 3 lights around each speaker and flashing bass ports. The spacing of the volume and bass dials could bot be changed so I placed them in the middle of the housing.

To difuse the lights around the speakers i used acrylic rod, drilled at one end at 5mm to accept the LEDs and sanded at the other with 400 grit wet and dry to defuse the light. The bass tubes are acrylic tube drilled 5mm again to accept the LEDs but this time the lenses of the LEDs have been sanded away as i want the light to diffuse through the side of the led and not protrude into the tube.

My design looked like the last picture on this step:
Hi sorry just one question........... the LED strip also supply's the power ( or whatever you nerd call it ;) ) to the + port thing of the speaker then u just wire the - as normal ...? if not ...please explain ? and whysand and drill 3 holes in the amplifier ? is that to attach the LED strip to also?
Ooh! This is awesome! <br>Also, the music choice = awesome.
very nice! <br>It is obvious you have many skills (electronics,woodcrafting,painting etc) <br>Cool mod, would fit nicely to any living room
Thanks, this project will be sitting nicely in my classroom in September
hi woody2k<br> nice project i have a suggestion that u can use transistors with a very high resistance at the base .. when u do this u will be able to use as many Led's as u can without dropping the sound of the amplifier or distorting it too... :)<br> btw keep up the good work....
The tip 121 transistor is a Darlington pair with a built in diode meaning that there is no feedback through the component and the signal is effectively amplified. I'm only running 3 LEDs off a transistor because they are in series, there is no problems with distortions whatsoever. <br>The LEDs on the bass tubes/ports are 2 series strings of 3 LEDs running off one transistor in parallel (6 LEDs in total)
very cool. how the quality of the sound from the amp you built compared to say, a 12 V &Acirc;&pound;30-&Acirc;&pound;40 car stereo amp?

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Bio: I am a Design Technology Teacher currently teaching Electronics but have trained / taught and studied everything under the D&T umbrella
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