Hi everyone,
I am just building an enclosure for my Mivoc AW3000 Subwoofer and want to make Leds which light to the beat of the music. I have got a Denon DRA 345R Amp with 2x65W. My Leds are 3mm wide and ae rated for 3V max. I have tried it before just connecting a Led with a resitor directly to the Amp but the Led blew up. I thought to use a switching Transistor for it but i am not sure. Hope you can help me.
The voltage is an AC type waveform with a varying amplitude and frequency depending on the sound. You need to assume that anywhere from 0 to +/- 22V AC could show up at the speaker side. Nothing you could use a voltage source but simple "color organ" type circuits might give you some hints on how to proceed.
http://www.jameco.com/Jameco/workshop/diy/ledcolororgan.html?CID=organ
and ae rated for 3V max
No they are not rated like this. That is a forward voltage drop NOT a rating.
You need a series resistor and a series diode as well as the LED. It sounds like you are killing the LED through too much reverse voltage. The series diode will stop that.
Ouch...
Assuming you have a (conservative) 16? speaker...
65W pmpo is about 46W rms.
Through a 16? load, that's about 1.7A at 27V.
For a 3V LED, you'd want to drop 24V. Assume a 25mA current for the LED, that's 24/0.025 = 960? at 0.6W heat dissipation.
Of course, it's all academic, cus it just won't work right anyway.
You need to have some filtering to obtain the right frequency response, plus more filtering to give a good signal for the LED, plus trigger level comparison...
Yes... take a good look at some of the colour organ projects around.
Of course, it's all academic, cus it just won't work right anyway.
Yes it will for someone who wants to do this sort of thing it will look fine. Just make sure you put the resistor / LED / diode combination across the speakers and it will be fine. Make it a 2K resistor.
Grumpy_Mike:
Of course, it's all academic, cus it just won't work right anyway.
Yes it will for someone who wants to do this sort of thing it will look fine. Just make sure you put the resistor / LED / diode combination across the speakers and it will be fine. Make it a 2K resistor.
Well, yes, you'll get light - but will it be the light you want?
A little active low-pass filtered LED driver I knocked up a while back:
Thx allot. Could I use an Arduino and programme it so it will react to the bass. As Analog Input I would a little microphone so the Arduino can "hear". Is this possible?
It is but frankly it is not worth it.
So I probably should use a color Organ. Can somebody tell me where to get an already built color Organ or a kit with printed circuit board.
The basic problem with a simple LED & resistor is that the brightness is proportional to loudness and you have an analog signal that varies with both the beat/music and the volume setting... You want the LED to blink brightly when the speaker/sub is running at normal listening levels, but you don't want to burn-out the LED (or have if constantly-on) at louder levels.
So I probably should use a color Organ.
FYI - A traditional color organ breaks the signal into 3 (or 4) audio bands, and with a different color light for each frequency-band. I'm sure that's OK with you, but only one of the channels will will respond to bass. (Of course, you don't connect it to your subwoofer.)
Can somebody tell me where to get an already built color Organ or a kit with printed circuit board.
I don't know... I think the first kit I ever built was a color organ, but that was a million years ago back in the analog days... After a few years I got bored with the effect and re-built it into a circuit that would change the color-pattern randomly on the beat.
While your searching, you might consider a spectrum analyzer or VU meter kit. ("Real" spectrum analyzers and VU meters can be expensive, but you're not looking for a measurement instrument, you're just looking for something to use as an "effect".)
There is a VU meter kit that runs off the speaker-signal (without a separate power supply), but I can't find the link at the moment
I'm not sure if you'll find anything that automatically adjusts to the level... Maybe... Most have a manual sensitivity control that has to be re-adjusted whenever you change the volume.
Some further thoughts...
Back to your original idea - I don't have a schematic for you, but you can make a circuit that blinks to the music and automatically adjusts to the volume-level, with a couple of op-amps.
An op-amp operated open-loop (without feedback) works as a comparator. You put a refrerence voltage on the -input, and your input/signal on the +input. Since an open-loop op-amp has (essentially) infinite gain, whenever the signal is less than the reference the output goes full-negative, and whenever the signal (+input) is greater than the reference (-input) the output goes full-positive. You can hook-up an LED to the op-amp's output so that it comes-on when your signal is greater than the reference and goes-off whenever the signal is below the refernce... Simple, right?
Now, another circuit you can build with an op-amp, diode, and resistor, is a peak detector. (You can find a schematic if you search). A peak detector charges-up the capacitor to the peak (usually positive) voltage and holds it. Peak detector schematics are usually shown with a switch to discharge the capacitor and reset the peak detector. But, in these applications the switch is replaced with a resistor so that the capacitor discharges in a fraction of a second.
So, we're going to connect the output of the peak detector to the comparators +input.
For compator's reference input, we can run the peak detector through a RC circuit (a simple low-pass filter) to slow-down and average-out the signal. Maybe we want a time-constant of 10 seconds or so...
Now, your LED flashes-on whenever the signal is louder than average and goes-off whenever the signal is lower than average. It's a simple effect, but it adjusts automatically and it works!
You can hook that circuit-up to a line-level audio signal. If you hook this circuit up to your a speaker signal, you need a voltage divider to keep the signal down below the op-amp's power-supply voltage. A resistor and a couple of "protection" diodes would be a good addition too. You might want to add some bias voltage to the reference input, so that it doesn't "try" to operate with no signal, or very-low signals. It might also work better if you use a separate peak detector for the reference, and a couple of op-amp buffers for each peak-detector output wouldn't hurt either.
If you use a microcontroller, you can do more... I recently finished an Arduino porject which is a string of lamps that works as a VU meter and also randomly switches between 7 other blinking/sequencing modes/effects. There are random options/variations of each effect, so for example the VU meter works in either direction (up or down) and it can invert, so that loudness turns the lamps off instead of on. It uses a peak detector with a buffered output (one dual op-amp), but the reference and automatic sensitivity-adjustment are done in software.