Re: Best way to power array of LEDs?

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#230

From: James Sweet
Date: Mon, 07 Oct 2002 06:50

38 lines
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The traffic light LED's use a transformerless power supply usually so they
flicker at 60 Hz, the yellow doesn't flicker because it's incandescent,
they're on so little that the savings of using LED's for them would be
minimal.

"AC/DCdude17" <JerC@prontoREMOVETHISmail.com> wrote in message
news:3DA03315.9506C177@prontoREMOVETHISmail.com...
> X-No-Archive: Yes
>
> Don Klipstein wrote:
>
> >   I do lots of rolling my eyes up and down to see some sense of light
> > output waveforms of all kinds of light sources.  I can definitely say
> > that pulsing is sometimes but usually not done in LED stoplights, and
> > especially not in most that see use at only one brightness level.
>
> The bus tail lights are two level.  When the headlight is on, it turns
into
> low mode just like any other car taillamps.  When you depress the brake
> pedal, it goes into high level.
>
> The little Trek flasher that goes onto back of my bike has two modes.
Steady
> and blinking.  When you put it on steady, the on-board IC actually drives
LED
> on pulse.  You can see it if you shake it in your hand and to prove it, it
> registers on my oscilloscope as pulsed voltage.
>
> Around here, red and some green traffic signals pulsates at rapid rate
> whereas yellow is steady. I'm suspecting they're running some kind of LED
on
> 60Hz.
>
> > And
> > I have driven and cycled behinnd enough buses!
> >
> >  - Don Klipstein (don@misty.com, http://www.misty.com/~don/ledp.html)
>

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Reply-To: "James Sweet" <jamessweet@hotmail.com>
From: "James Sweet" <jamessweet@hotmail.com>
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