RE: LED at 60 HZ? (was RE: Radio Shack Strobes)

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Philip Chalk" <phil-at-apsecurity-dot-com.au> 


Yep, done that, works fine.  Again, especially at mains voltages, you
need to protect the LED from reverse voltage with a parallel diode,
connected 'opposite' to the LED.

Phil Chalk.


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, 25 February 2004 12:32 PM
To: tesla-at-pupman-dot-com
Subject: RE: LED at 60 HZ? (was RE: Radio Shack Strobes)

Original poster: "explorecraft" <pariah-at-explorecraft-dot-com>


Anyone here tried wiring an LED straight off the mains with
   a capacitor <in series> chosen for its reactance at 50 or 60 hz?

I thought choosing a cap with a reactance to drop the
   current down to the 40 mA level would do the trick.
(I wanted to do something like that to drive my planned
   primary, a flourescent circular tube, matching the cap
   reactance at the resonance to limit tube current)

<My next fireworks show, perhaps>

  > -----Original Message-----
  > From: Tesla list [mailto:tesla-at-pupman-dot-com]
  > Sent: Wednesday, 2004 February 25 06:45
  > To: tesla-at-pupman-dot-com
  > Subject: Re: LED at 60 HZ? (was RE: Radio Shack Strobes)
  >
  >
  > Original poster: Jerry Chamkis <jchamkis-at-bga-dot-com>
  >
  > It's true- an LED will work fine.  Regular LEDs turn on and off
  > plenty fast
  > for this application but there might be some question about
  > -some- white LEDs
  > that use a UV-excited phosphor.
  >
  > Two things to keep in mind though-
  >
  > 1.  You must protect the LED from reverse voltage.  You can
  > either put a diode
  > in series or a diode in parallel facing the opposite way of the LED.
  >
  > 2.  You must limit the current through the LED so a series
  > resistor is also
  > required.  You may get away with powering it directly from a (very)
small
  > transformer because it can't supply a huge amount of current, but
that LED
  > won't die of old age!  You can probably get away with 50 - 100 ma
peak
  > current through a full-size LED and of course it's perfectly
acceptable to
  > use multiple LEDs for increased brightness.
  >
  > Jerry
  >
  > On Tuesday 24 February 2004 02:10 pm, Tesla list wrote:
  >  > Original poster: "Daniel Kline" <daniel_kline-at-med.unc.edu>
  >  >
  >  > An engineering friend says a high-brightness LED on a
  >  > low-voltage transformer, like 6 Volts, connected through
  >  > a suitable resistance, should flash at 60Hz in sync with
  >  > the 60Hz mains. (50Hz for you all over there :)
  >  > It seems too easy to me...he thinks that the LED may have
  >  > a "persistence" issue. In other words, just because it
  >  > turns off quickly doesn't mean it stops emitting quickly.
  >  > Comments?
  >  > Thanks,
  >  > Dan K
  >
  > --
  > Jerry Chamkis
  > jchamkis-at-bga-dot-com
  >
  >
  >
  >