On Thu, 18 Sep 1997, Martin R. Green wrote:

PTM: Sorry, I was in a hurry and didn't select my words. (english is not
my native language:)
I mean that I made some years ago some experiments with various light
sources. I wanted to have as clean light as possible. I was disapointed
with bulps. There came very annoying 100 Hz ripple. (we have 240V 50Hz)
Then I made another try with a diode in series with a bulp and got 50 Hz
half vawes as I expected. Only that their 'duty cycle' was less than 50%
because it took time for the filament to warm up. This 50 Hz is twice the
frequency that is needed in movies to make flickerfree picture. Still it
made an awfull flicker.
I continued my expertiments with a capasitor. In parallel connection with
a bulp and a diode in series with them I got a little better results =
cleaner light. With a triac and thyristor -power (zero point) I got very
much flicker.

The cleanest light I got when I connected three bulps in three phase line.
Another good method was using higher frequency. That was however
impossible those days, because we needed rather high power.

These stroboscobes in the LP players have very often been just ordinary
bulbs with rather thin filament (low power, 220V). I have myself use
normal 220V/60W when I check the speed of small synchron motors.
I know that fluorescent tubes are forbidden when you work with electric
tools. It does make sense.

> Pasi, I'm not sure what your point is here.  Are you saying that I'm wrong?
>  You don't need to check the light output with an LDR and a scope.  All
> that will tell you is what the light is doing, not what effect it has on
> the human eye.  And I speak based on past experience with stroboscopic
> effects of various light sources.
>
> Also, I'm talking about normal lightbulbs hooked up to straight mains
> power.  Why are you introducing all sorts of variables like resistors,
> diodes and triacs?  Read the original thread.
>
>
> Martin R. Green
> elimar@bigfoot.com
>
> ----------
> From:   Pasi T Mustalahti[SMTP:ptmusta@UTU.FI]
> On Wed, 17 Sep 1997, Martin R. Green wrote:
>
> > As far as lightbulbs go, they are not really affected by flicker because
> > the hot filaments have a very long persistence.
> PTM: Try this first. Take a Oskilloskope and a LDR. Speak after that.
> I Tried myself with bulps with various wattage, with series resistors,
> with series diodes and TRIACS.
>
> Fluorescent lights,
> > however, do pulsate in time with the AC frequency.  This is why those
> > strobe rings on  LP turntables don't work with incandescent light.  You
> > need fluorescent or neon illumination to set the turntable speed with
> this
> > method.
>
> PTM: Try first, speak after that.

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