Flickering LEDs

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Flickering LEDs

Postby Panrock » Mon Oct 07, 2013 5:43 am

Can anyone suggest a source for component flickering LEDs (ie. not the complete 'candle' style lamps containing them)?

I have to make an impulse noise 'crackle' sound generator and I thought using a flickering LED might make a simple way to get started with this.

Cheers,

Steve
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Postby Klaas Robers » Thu Oct 10, 2013 7:53 am

Steve, try once to connect an earphone to the wires of the LED in such a flickering candle. I know that in certain cases you will hear...... music.

At least in the beginning the constructors of those candles used the very cheap chips of the "Happy Birthday" music cards, to modulate their LED. I expect that in the mean time special chips have been developed for this function, but it was very surprising to get music out of such a candle.
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Postby AncientBrit » Thu Oct 10, 2013 5:39 pm

I like that idea Klaas.
I'd never have thought of it myself.

Shows lateral thinking on the part of the designer.

Regards,

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Postby Klaas Robers » Fri Oct 11, 2013 12:06 am

Right Graham,

isn't this what we call: "Thinking out of the box"? Is that the same as "lateral"?
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Postby AncientBrit » Fri Oct 11, 2013 5:23 pm

It is indeed Klaas,

Regards,

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Postby Panrock » Fri Oct 11, 2013 8:29 pm

I've got a flickering candle lamp from Maplin now - no sign of a source of the actual LEDs yet - and will let you know what I hear ! :)

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Postby Panrock » Thu Oct 17, 2013 3:11 am

Well, THIS is what the flickering light from the LED sounds like, as picked up with a club dome cell...

So it's not suitable for my needs.

Intentionally generating 'static' type impulse noise seems difficult!

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Postby DrZarkov » Fri Oct 18, 2013 3:16 am

There are kits available to produce e real static noise. Those circuits are not very small, easy or cheap: http://www.elv.de/velleman-k4301-rosa-r ... usatz.html

Of course there are much easier ways: http://en.wikipedia.org/wiki/Noise_generator , but that is not a perfect Pink noise.
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Postby Panrock » Fri Oct 18, 2013 8:22 am

That Velleman kit is a pink noise generator. It does not produce the 'static'-type 'impulse' noise I am looking for... resembling ignition interference.

I once made a fancy pseudo-random noise generator with gates and what-have-u. It worked, but for generating ordinary noise, I think this simple circuit is better...

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Postby Panrock » Mon Oct 21, 2013 4:53 am

I am now going to try triggering a monostable (with a short time constant) with 'delicately applied' noise. Maybe that'll give me what I'm looking for.

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Postby Klaas Robers » Mon Oct 21, 2013 7:11 am

What type of noise are you searching for Steve? The type of noise that a Geiger-Mueller counter makes? Or ignition noise of a motor bike, which has a more repetitive character?
What is your aim?
Where do you want to use it for?
How random should it be?

White noise and pink noise can also be found on the NBTV-CD number 1.
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Postby AncientBrit » Mon Oct 21, 2013 5:59 pm

Steve,

I think you'll need to LPF the noise to restrict it to the region of say 5Hz to 100Hz, then as you say use this to trigger a mono with a short tc to produce the impulse type signal you're after.

Cheers,

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Postby Panrock » Tue Oct 22, 2013 6:43 pm

Klaas Robers wrote:What type of noise are you searching for Steve? The type of noise that a Geiger-Mueller counter makes? Or ignition noise of a motor bike, which has a more repetitive character?

Either would do, I think.

Klaas Robers wrote:What is your aim? Where do you want to use it for?.

This is to form part of a tinnitus cancellation device. This is not a tinnitus masker. See www.detinnitiser.com for more.

Klaas Robers wrote:How random should it be?.
As random as possible.

AncientBrit wrote:I think you'll need to LPF the noise to restrict it to the region of say 5Hz to 100Hz, then as you say use this to trigger a mono with a short tc to produce the impulse type signal you're after.


Thanks for this useful tip. I'm to build the breadboard today. I'll try both with and without the LPF. However, since this is a commercial venture, you all may feel discussion to be inappropriate on a hobbyist site like this. Upto you. :)

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Postby Klaas Robers » Wed Oct 23, 2013 1:23 am

Then why not storing some pulse sequence in an EPROM, read that out with a counter as address (4040). When it repeats after several seconds, who cares? You may program the pulse sequence bit by bit or use the RND function of your computer to make something. Then you may use that to trigger the one shot.
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Postby AncientBrit » Wed Oct 23, 2013 5:48 pm

Steve,

I've no problems in discussing projects with a commercial outcome.

I like Klaas's EPROM idea though.

Cheers,

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