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Re: [APD] ODNOS
If those are the "findings" I've seen before, I doubt the measurements. So do the electrical engineers I've talked to that have are familiar with the operational fundamentals of fluorescent lamps and those that have done some overdriving themselves to assess the effects. Within normal design operating range, a bulb will be more efficient if it runs a bit hotter than if a bit cooler -- too much fanning can slightly dim bulb output as can very cold weather. Once the mercury is fully vaporised and the plasma formed, futher increases in temperature have little effect on brightness but more dramatic effects on mercury capture (in the phosphors and glass) and on filament deterioration, production of infra red (heat) and all the things that confound the desired ideal result of more UV photons being created in the plasma, being absorbed by the phosphors, which in turn emit lowe energy (visible) photons..
When you "overdrive" the bulbs, you set up a situation that forces a higher than "normal" voltage across the bulb to drive more current through it -- the plan is to get a whole lot more electrons racing through the plasma and "knocking off" more photons and hopefully more of them in the UV range rather than the infra red range because its the UV photons that make the phosphors fluoresce. But when you get up in the range of overdriving, you start paying a price for operating a bulb so far out of it's design parameters. You can get more light out of a bulb by overdriving it but you use up proportionally more energy to do it -- i.e., more of the electrical input is shed as heat.
Of course, which bulbs and ballast you are using will make a diff in the specific results that one will see. Bulbs and ballasts interact to "set" a voltage across the bulb and control the current.
Iirc, there's bunch of stuff on this in the archives.
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----- Original Message ----
From: Paul M Wallace <pwallace at u_washington.edu>
To: aquatic plants digest <aquatic-plants at actwin_com>
Sent: Friday, December 16, 2005 12:32:42 PM
Subject: Re: [APD] ODNOS
Sounds like you might not be using the right ballast. This article from TPT shows how to do ODNO and discusses measured output.
The finding is that measured power is less than expected so the bulbs do become more efficient.
On Thu, 15 Dec 2005, S. Hieber wrote:
> One factor might be that the efficiency declines as you
> overdrive so doubling the power won't yield a doubling in
> light output.
> Some ballasts can limit current even if you try to
> overdrive them and that could be coming into play also.
> --- "Joshua L. Wiegert" <JLW at dune_net> wrote:
>> Okay, I've got four overdriven 40W lamps on a 55-gallon,
>> and finally got
>> around to setting it all up. I hate to say this, but it
>> looks like a lot of
>> trouble for not much. :) The lamps get warmer,
>> definitely: but I don't see
>> a lot of difference between 4x40 OD and 4x40 standard. I
>> shut it down to
>> one bulb, and compared to a standard one I have -- cast
>> it at the ceiling
>> from the floor, and both looked about the same. I even
>> tried the
>> ink-through paper test (take several sheets of thick,
>> white paper, and write
>> something on the bottom one. Hold it over a lamp, and
>> lift it until you can
>> no longer see what is written on the bottom sheet.
>> Measure the distance.)
>> The difference between teh ODNO and the standard was
>> marginal, and may very
>> well have been more due to the fact that the standard
>> bulb was older and had
>> some water marking on it.
>> Have I stumbled onto some sort of smart ballasts that
>> know how many bulbs
>> are on them, and aren't cooperating? :) These bulbs
>> should be twice as
>> bright as a standard flourescent, right? So far, all
>> I've managed to do is
>> find a way to use a flourescent as a heater -- they get
>> much warmer. Did I
>> wire something wrong, or am I just not able to perceive
>> the difference in
>> light output?
>> Who probalby should have just bought the cheap PC dealy.
>> Joshua L. Wiegert
>> Native Fish Conservancy Lists Administrator
>> JLW at dune_net
>> AIM UID: JoshuaWiegert
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