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

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

Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

Just a suggestion:

On 25 Feb 2004, at 7:21, Tesla list wrote:

 > Original poster: David Speck <dave-at-davidspeckmd-dot-org>
 >
 > Eric,
 > Way too much work --
 >
 > Just use a few high brightness red LEDs in series, and drive them with
 > a 12 volt transformer from the control panel of a scrapped microwave
 > oven. 8 or 9 red LEDs at 1.8 volts typical forward drop will light
 > only at the peak of the waveform, and give you an adequate strobe
 > effect.  A white LED does use a phosphor which will glow for a long
 > time after it is de-energised, and will not work suitably.
 >
 > HTH,
 > Dave
 >
 > If you have enough in series, they won't conduct till nearly the peak
 > of the 60 Hz sine wave, giving you a narrower output pulse width.
 > Include one standard rectifier (1N400X) in series with the string to
 > provide reverse voltage protection.

You could have two strings in anti-parallel to give double the
frequency. I suppose it hardly matters at such low power levels but
running a single string leaves a DC component in the
transformer/mains. I built a set of lights for our Christmas tree a
few years ago and that used four strings of 10 LEDs/string, two in
parallel each way straight across a small plugpack transformer. The
brightness of the display determined the number of LEDs to use and
yes, the eye sees it as a continuous glow - until you move your head.

Malcolm

Malcolm


 > > > heres an idea, tie enough diodes in series with it so that it
 > > > drops the voltage to whatever the led needs. Say it wants 1 volt.
 > > > 120 - 1 = 119 volts that need to be dropped. 0.6 * x = 119. 198
 > > > would be suitable for x. It would need alot of 1n4007 in series
 > > > with it, but the led would receive power only at the top of the
 > > > waveform.
 > >
 > >Does it sound like a good idea?
 >
 >
 >
 >
 >
 >