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> 

On 24 Feb 2004, at 13:10, 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?

The persistence can't be great considering LEDs are used to convert
electrical impulses to light impulses at GHz frequencies. Any
perceived persistence is probably a function of propagation time from
eyes to brain or some other physiological thing to do with the eyes.

Malcolm