Art Todesco wrote:

Jeff Wisnia wrote:

James Sweet wrote:



It prolly wouldn't take a very big electrolytic capacitor to level
those current pulses out, huh?

Easy to do fer your own strings I guess, but that doesn't help for
all the others you have to look at.

Fortunately that 60 Hz flicker rate is above what triggers
photosensitive epilepsy in most persons sensitive to that.

http://www.epilepsy.org.uk/info/photo.html

Jeff




Don't even need a capacitor, a simple bridge rectifier changes it to
120Hz flicker, pretty much not noticeable unless you scan your eyes
past it quickly.



My thinking wuz that by using just a cap, you wouldn't change the
total energy delivered to the string of LEDs significantly, but with
full wave rectification you'd double it and possibly blow an LED if
the original design had them powered pretty close to their safe limit.
Capice?

Jeff

Good thought! But you have to put a diode somewhere to protect the
electrolytic capacitor from seeing AC. I guess you could "sacrifice" the
1st LED and put the capacitor after it. But, there are parallel and/or
series
resistors in the sockets, so you have to be carefull. A separate diode
would probably be best.

That shows another this Jew doesn't know about Xmas, I've never examined
a string of LED lights to determine just how they work. G

I'd assumed there was a half wave rectifier and maybe a series resistor
there already there, to avoid exceeding the LED's PIV ratings.

But maybe they avoid that with a parallel diode across each LED and a
single series resistor for the whole string, that's similar to what I
found inside one of our white LED nightlights when it started acting
funny because the LED was having a nervous breakdown. (It stayed dark
even though plugged in, but flickered on when I switched an inductive
load on the same circuit - a bathroom vent fan.) Soldering in a new LED
fixed that sucker.

Anyway, you got my point, full wave rectification would most likely
double the power dissipated in the LEDs if everything else in the
circuit stayed the same.

Jeff

--
Jeffry Wisnia

(W1BSV + Brass Rat '57 EE)

"Truth exists; only falsehood has to be invented."