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Re: [APD] Re: Over driving lights (again)

>From what I've read, it would be hard to get a full 100%
increase in light output no matter how hard you drove the
bulbs. As you drive them harder, they get hotter and the
plasma resistance drops further but the phosphors perfotman
worse as the temperature rises.  After a certain point you
run into what's called "thermal runaway" and you just can't
get enough juice into the bulb to make the phosphors

It might be possible that the most stable of the phosphors,
those in the "green" (and the ones humans are most
sensitive to) hold on the longest, but that doesn't help
the plants much. I'm not saying you can't get brighter
light from running more current through a fluorescent. I
just doubt that the physics is there for most bulbs to
achieve double output for any reasonable length of time.

I would guess that at 2xs you might have 40-60% increase
and another doubling of input energy ight bring you another
20%, and the marginal return continues to decline as the
input energy increases.

Just what the percentages are will vary with particular
bulbs and ballasts, but basically the harder you push the
rock uphill, the heavier the rock becomes.

Not certain I'm right, just doubtful that I'm wrong on this

I wouldn't mind seeing measurements in the PAR regions on a
lot of diff bulb ballast combinations -- including the
design combinations like four F32T8s on a 4x32-F8 ballast
-- I suspect some of those results would be surprising. It
would be nice to know just what happens and how wide the
range of results are.

As for the "old" post -- Ah yes, Wayne left a lot of good
stuff on APD before left the list -- and not jsut stuff
about lights.  Anyone know where he is? 

Based on his results, in his example, at 4 times overdrive,
he had more than double output (2.35) or roughly double,
(1.8-2.4 more or less) given his estimated margin of error.
He didn't discriminate frequencies in his measurements but
he was measuring lumens which is weighted to human eye
sensitivity (did I get that right, Wright?).

Other ballast bulb combinations might do better but I
suspect they won't do double unless the bulb is rather
underdriven to start with as is the case in Wayne's

Did I ask if anyone knows where Wayne is?

Scott H.

--- Giancarlo Podio <gp at isaconsulting_com> wrote:
> Scott,
> I don't have a light meter but based on my camera's meter
> the amount of
> light emitted at x2 OD is closer to double than I had
> expected. Three months
> down the road now and I have yet to notice any drop in
> light intensity. If
> the lamps last 6 months I will consider it a very valid
> alternative and will
> keep the fixture as is.
> There is also this post from the past with more detailed
> results:

S. Hieber

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