[sdiy] bunch O' LEDS

[phil macnutt]

It's probably dangerous and illegal, but it does work. Now matter how many I
connect, they all are the same intensity, and the overall current matches
what I would expect for the number of diodes.

-----Original Message-----
From: owner-synth-diy at dropmix.xs4all.nl
[mailto:owner-synth-diy at dropmix.xs4all.nl] On Behalf Of Scott Gravenhorst
Sent: Friday, February 24, 2006 3:53 PM
To: synth-diy at dropmix.xs4all.nl
Subject: Re: [sdiy] bunch O' LEDS

Well, I always thought that when diodes are connected in parallel (without
series
resistors), they don't "share current" like resistors do.  One diode (of a
pair) will
turn on and it's dynamic resistance will limit the voltage across the other
one to a
value below what is necessary to turn it on.  

But since I'm here to learn, I'm making this statement in hopes that if it's
wrong, I'll
get educated.

"phil macnutt" <philmacnutt at mac.com> wrote:
>Ok guys, I need a little help.
>
> 
>
>Sounds weird, but I need to drive a bunch of leds with a pitch CV.
>
>For example I'd like the LEDS to see 0-1 amp (50 leds)  corresponding  to a
>0-2volt input.  The LEDS are all in parallel, and do not have resistors on
>each one.
>
>I poked around and found a really simple circuit that is nothing but an
>opamp and a single resistor that does this V-C conversion.
>
>Works great, but the amp could never drive a whole stack of leds.  So, I
>guess I need a circuit that I can use a power transistor with at the output
>and some sort of pot to adjust the sensitivity (based on the CV range).
>
>If anybody knows of info already on the web regarding this, just point me
in
>the right direction
>
> 
>
>On another topic, I'm currently experimenting with various paints for
>silkscreening front panels, and I should have some information on which
>paint is best if anybody is interested.  I got my screens from Westar, and
>they look great.
>
> 
>
>Thanks in advance for any assistance!
>
>phil
>
>

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-- Scott Gravenhorst | LegoManiac / Lego Trains / RIS 1.5
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