LED fun

hello. for a while I've wanted to stick some LEDs in my speakers, to get brighter and darker in accordance with the volume they play at.

so I just wanted to run a couple of things by people to check what I'm planning to do in case someone can suggest alterations/improvements or point out potential problems.

the reasons I want to do this; a) it looks cool (if done right) b) it will help with fault finding; if there's no sound but there's LEDs, I at least know the signal is getting down the cables.... c) for fun.

I guess the way to do it would be to have a separate circuit in parallel across the driver, comprising of 3 components:

LED - for light!

Resistor - to ensure the voltage across the LED doesn't exceed it's specified limit at max volume/voltage

A fuse - I'm thinking this would be required to ensure that if the current becomes too large, the fuse breaks down and not the LED. b ut I'm not certain.

PICTURE:


(approximate values for example: R = 2k5, for an LED which can take max around 3V.. for a 400ishW driver running at max (this needs woking out for peaks to make calculate for 600W to be safe) with around 60V across it)

this would make an almost negligable change to the resistance presented to the amplifier, ie, 7.9Ohm as opposed to 8Ohm.

the assumptions I'm making here:

When you apply a reverse voltage (the other way) to a diode it presents an infinite resistance...?

If I apply too high a voltage to a diode it will short rather than break the circuit - hence the fuse required

The LED will be flashing but at a fequency above 50Hz or so which it always will be for these applications, so it will be un-noticeable so no need to put some kind of rectifier in there to make it DC and constant.

Problems:

if the driver voice coil breaks: - then the amp will just see a resistance of kilo Ohmsish - equal to the resistor value.... so what happens? can this damage the amp? I guess not it will just heat up the resistor, perhaps I can set the fuse to blow at this point.....

if the fuse blows, no problem.

QUESTION:

This might be a silly question but: the above circuit will mean that when a forward voltage is applied to the LED, the resistance seen by the amplifier will be ever so slightly lower than when a reverse voltage is applied (since the current can only pass through LEDs in one direction). this in turn will mean the amp sees an alternating resistance??? will this be noticeable or not volume-wise from the driver? I think not, the change in the resistance is pretty negligable. feel like I'm saying silly things here. been typing too long...


hopfully this makes sense. perhaps it's done completely different to this usually but this was my guess. perhaps I don't need the fuse - just not sure what happens to an LED if it breaks down and I don't want to short the amp.

any help would be great. BIGUP

EDIT:

LINK

GOOD CALL.

Edited by bassmish - 18 November 2011 at 12:22am