Reply-To: "James Sweet"
From: "James Sweet"
References: <0001HW.B9C26E7400A7161B165FEAC0@news.covad.net> <3D9D3A1F.97DB97B4@prontoREMOVETHISmail.com> <3DA03315.9506C177@prontoREMOVETHISmail.com>
Subject: Re: Best way to power array of LEDs?
X-Newsreader: Microsoft Outlook Express 6.00.2600.0000
NNTP-Posting-Date: Mon, 07 Oct 2002 06:50:30 GMT
Organization: AT&T Broadband
Date: Mon, 07 Oct 2002 06:50:30 GMT
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
"AC/DCdude17" wrote in message
> 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
> 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.
> and blinking. When you put it on steady, the on-board IC actually drives
> 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
> > And
> > I have driven and cycled behinnd enough buses!
> > - Don Klipstein (email@example.com, http://www.misty.com/~don/ledp.html)