Looking to Make LEDs Pulse to Bass in My Car

So basically,

I have 4 LED strips (each rated for 12v) that I'd like to make pulse to the bass of the music, such as in this video http://www.youtube.com/watch?v=o_IEz2T1SiY. There are a lot of misinformed people on YouTube who just hook up their LEDs directly in parallel with the subwoofers, which doesn't work well at all and will blow the LEDs, so YouTube hasn't been much of a help to me.

I'm just a first year EE student, not a full on EE like most of you guys probably are, so I was wondering if anybody would be able to help me design a circuit to make this work. A threw this together, it is by NO means even remotely correct, just a little visualization of what I'm trying to do here. I think I'm probably going to have to end up doing something with a transistor for the switch, and a capacitor to make the LEDs fade after the bass hits, but I'm not really sure.

Some things to note:

* Each diode in that circuit represents an LED strip rated for 12v DC
* My amp is 3000 W peak power
* There are two subs wired in parallel with a total impedance of 4 Ohms.

Any and all help/suggestions is much appreciated!

Thanks

Oh for gods sake !! Show them how to do something properly for a change will you

Here Build a low pass filter and attach to a transistor which drives the led' s for crying out loud Collin must you take the piss all the time out of them

You want a beat extractor circuit then what you do is attach this to a drive transistor to power the led's


Also without being rude to you either you ae strictly speaking supposed to be a first year EE student as such you ought to know at least this much or at least know how to draw a block diagram I mean this is city and guilds basic bloody level (Part 1 ) Christ what have we got here Is this what the new generation is going to bring so to be honest whilst I don't like what Collin does sometimes I can see why hes doing this perhaps he too also thinks your a piss taker

Also to be honest with you I also get annoyed when I see this because I see this standard every day and I too know full well what you have to learn but when you make no effort and don't want to listen or learn Im very much the same and I'm am also dead bloody sarcastic and in laymen s terms dead fucking rude because Ive also had it with some of you

Example Input >>> Low pass filter >>> Power drive circuit >>> Display

Here let me help you a little Its really not that difficult

http://www.google.co.uk/imgres?imgurl=http://...rUZvVCenJ0QXL-YDoDQ&ved=0CGYQ9QEwBw&dur=13674

Probably don't need the low pass filter if this is strictly a sub-woofer output. The high frequency content will already have been stripped out. So, I don't think it needs to be as complicated as you have suggested, Mark.

And if the high frequency content _is_ intact, a simple RC filter should be enough.

Haha ok, lets take this down a notch, jumping to all these conclusions based off little info is a bit unnecessary. This has been a learning experience for me, mostly from other forums because I haven't been getting much help here. This what I have at the moment:

After sleeping on it...

bq). Each diode in that circuit represents an LED strip rated for 12v DC

Why the 100Ω resistors in series with the LEDs. If each LED "diode" symbol represents a 12V LED strip, then wouldn't you want to connect the LED strip directly to 12V and not through a current limiting series resistor?

Also, I would use something like a 1N4004 instead of the 1N4148. The 1N4148 has a PRV of 100V and the peak voltage from the speaker can go as high as 90 - 110 volts. That's cutting it a bit close (doesn't allow for spikes, and such, riding on top of that voltage). A 1N4004 has a PIV of 400V--much more robust. And, at these frequencies (i.e. sub-woofer) there is no need for speed.

Otherwise this circuit looks like it should work -- if the LEDs don't light up some of the time (when they "should") then try reducing the value of C1 -- that will shift the cutoff frequency higher (of the RC low-pass filter).

The addition of a sensitivity control is a nice touch.

Not that you are going to go with this (because your circuit is actually better but just in case, here's a refinement:

Thanks for the reply! Yeah, I forgot to take those resistors out of the schematic but they won't be there when I actually build it. Thanks for the advice on the 1N4004, I'll definitely give that a try instead and get some more caps if I need to reduce C1. It is going to take a while for all the parts to get here unfortunately, but once I get it built (assuming it works) I'll post a video here showing it in action

Oh, quick question. Assuming I did my circuit, what should the W be on them? I see how you labelled yours 1/4W, do you have any idea what the ones on mine should be?

Well, if the peak power is 3000W and lets say the average power is 500W (volume not all the way up and music that is not always a full level).

P = E²/R: E = √PR = √500*2 = 32V so that is the average voltage across the 50K pot
P = E²/R = 32²/50k = 20mW so, for the 50K pot, anything above that.
And I can already tell you that for the 47K and 220K resistors it's going to be less, so 1/8th watt and above.

Even if the average power were to get to 1000W:

P = E²/R: E = √PR = √1000*2 = 45V
P = E²/R = 45²/50k = 40mW so still the same

I can't imagine the average power going any higher that that, but if you think so, you now know how to do the math.