Jan-erik Soderholm (QAC) wrote:
> Wagner Lipnharski wrote:
> [about only switching TRACS'at the zero crossing pont]
>
> Sounds interesting !
> Just a minor point...
>
> Take this setting as an example :
>
>> Cycles ON   Cycles OFF    % Power  Status
>> ---------   ----------    -------  ------
>>    5          4             55       m
>
> Here, we have a "blink" frequency of 1 / (9 * 0.20) =
> aprox 5.5 Hz. Now, I don't know if this is visible,
> but, as having a son with epilepsy, I know the *some* people
> are very sensistive to flickering lights, even those
> not *visible* to us "others".
>
> As an example, when taking out money at the automatic
> teller machine, my son can't look at the screen, just
> becuse someone selected to use a "low cost" CRT with a low
> scan freq in the unit.
> And he can't look at a 50Hz TV set, it have to be a 100Hz set.
> On his computer we have installed a LCD screen, and so on.
>
> Anyway, what I ment was that we should be easy with
> flickering lights, because there are many "out there"
> that has big problems with them...
>
> Jan-Erik Soderholm.


I agree with you, but there is a difference in response time from a CRT and
an incandescent lamp.
The CRT phosphor should react very fast, well, at least for our eyes, its
"persistance" should be enough to allow the trace to scan all the image and
get back, I guess it is no more than 1/20 of a second.  The persistance of
a incandescent lamp is a little bit higher, I guess more than 1/2 of a
second, mostly for lamps 100W or more.

The 1/9 blink "off" rate would be 60/9 = 6.66 per second, with a "off" time
of only 16.66ms.

Recently I built a SMT soldering oven with a 800ms PWM rate.  When the
thermal elements are bright red, and reach the desired temperature, the
electronics (an AVR and a solid state relay) keeps the temperature floating
via a glass NTC sensor into the oven.  Even with a 50% power applied under
a gross power control (zero crossing at the relay), you can only notice the
neon lamp blinking at the front of the oven, the elements just reduce the
red bright, but no cintilation at all, even with 800ms of on/off.  Of
course, that is not a lamp, and the persistance is much bigger than a
regular incandescent lamp.  The oven control is not in sync with the power
lines single sinewaves, just a crude PWM with a resolution of 800ms.

<out of control brainstorming>

I wonder why, up to now, nobody produced any kind of glasses using lenses
made from some kind of translucid fluorescent polymer with a capacity to
store photons energy for some milliseconds.  Even being a very difficult
task, including wide spread light wash (all over the lens) and monochrome
lag, in time and technology, it could help somehow the epilepsy people who
suffer with light cintilation.  Even gel contact lenses (with or without
correction degrees) could be produced for this purpose.  The counter effect
is the viewed image turns to be a little greenish, but in time the brain
compensantes it.

</out of control brainstorming>

Wagner.

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