Instructables

Musical Lights


Hey,
I recently saw http://www.youtube.com/watch?v=Yd3hzYAJzOo&w and i want to make that.
I read the schematic at http://www.uploderx.net/dphrag/SCHEMATIC1___PAGE1444.jpg (that link doesn't work, use this one: http://www.buildlounge.com/wp-content/uploads/2011/10/xy88F.jpg  for it, but, I'm still quite confused.
The parts that are the most problematic to me are the high, low, and mid pass filters. i  don't understand what they are, and how there made.
If anyone could help me, thank you.

The schematic link gives a redirect loop, or a picture of a smiley.

The filters allow different frequencies through to switch on the light. In its simplest form, a filter consists of just a capacitor and an inductor, the values of which (capacitance and inductance respectively) affect the frequencies blocked or passed.
schumi23 (author)  The Skinnerz3 years ago
sorry about the schematic's link, this one should work: http://www.buildlounge.com/wp-content/uploads/2011/10/xy88F.jpg
Otherwise, do you know what the formula to calculate which frequencies are blocked would be?
And many thanks for your help.
am too waiting for those filters stuff the normal thing is very easy to make LED box

but making it react differently by means of mid - low and high is difficult to understand am searching from days and to no success can anyone help
schumi23 (author)  samalert2 years ago
Well, i have sorta found it. For a low pass filter, it is just a capacitor in parallel with Leds (connecting the 2 power wires).
Since capacitors do not let DC current pass through, and they also do not let low frequency through, depending on the value of capacitance of it.
Instead of trying to find formulas, as they were never for setups that simple (always had a resistor in the formula)(lol, i'm an idiot, i just realized, i do have a resistor for the LED, i could have just used that :( )

I just tried putting different capacitors in parallel, and with a tone generator (I used Beeplayer which is free (available here: http://houbysoft.com/en/downprog.php#beeplayer)) at the cutoff frequency that i wanted, and tried putting various caps that i had from de-soldering them from broken electronics, and found one that had that cutoff frequency (the cutoff frequency is when the frequency response is less then 70% (70% of the signal is blocked)
If you want somewhere to start, a 1000UF capacitor gave me a Cutoff frequency of 80 hertz.

Also, a goodish guide (its just for active filters instead of passive) is here http://www.ti.com/lit/an/sloa093/sloa093.pdf.
Hope it helps.
Also, in theory, a high pass filter could just be a capacitor in series with the leds, but, through extensive (ok, through testing 5 possibility)i have yet to find on that would let any audible frequency through.
schumi23 (author)  The Skinnerz3 years ago
Also, looking at the schematic again, could you tell me what the symbol marked Q1, Q2, and Q3 represents?
Also, what are the 4 symbols marked VDD represent?
(sorry for the double post, i looked for an option to edit a previous post, but didn't find it, if it exists, please tell me about that)