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

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

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
 >
 >
 >
 >