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Re: Cheap, strong light?


>Date: Thu, 28 Aug 1997 09:29:19 -0700
>From: "Frank I. Reiter" <FIR at istar_ca>
>
>Browsing through a hardware store yesterday, I came across some halogen
>lights and suddenly realized that I have never heard any mention of
anybody
>trying them over an aquarium.  With there being no expensive, bulky, noisy
>ballasts, and with 500W bulbs costing $4.00, somebody must have tried
them.

There are some good articles on halogens in the APD archives to check out.

>Does anybody know anything about the spectrum that these things put out,
or
>failing that, how I could find out?

Okay, here's the thing about halogen and other incandescent bulbs.

Halogens and incandescent bulbs are a blackbody-type radiation source.
They emit light energy in all wavelengths from the deep infrared up to
their operating color (color temperature, effectively).  Halogens run at a
hotter temperature than normal incandescents because the gas in the bulb
helps prevent filament degredation at the higher temperatures.  This gives
them a higher color temperature than say, a normal 40w, 100w, ...
incandescent.

A large part of the energy emmitted by incandescents comes out in the deep
infrared range.  Some of this energy is useful to plants, but some probably
isn't.  

What you get out of an incandescent light is a CRI of 100, every time.
It's just the way they work.  They acheive this by emitting light in every
wavelength.  In order to do this though, they use a lot more energy than a
fluorescent or other plasma discharge light that restricts most of its
output to the visible spectrum.  

In terms of efficiency, well, that depends on what you want.  An
incandescent will emit 100% of the energy it consumes, minus conductive and
convective losses.  The challenge is that a big part of this is not visible
light.  A plasma discharge has additional, small energy losses at the point
of the ballast, where the energy is dissipated as infrared or by
conduction/convection.  An additional, fairly small percentage is radiated
as infrared from the light source (tube or bulb), but a very large
percentage, comparatively, is emmitted as visible light.

I've heard of great successes using incandescent lighting.  The thing is,
your tank won't be as bright per watt-hour consumed, and you may run into
heat problems.

I use fluorescents and would consider other plasma discharge lighting.  If
I want to do incandescent, it will be experimentally on a very small scale,
or it would be using direct sunlight.

I hope this helps some,

David W. Webb           Texas Instruments
(972) 575-3443 (voice)  http://www.dallas.net/~dwebb
(214) 581-2380 (pager)  2145812380 at alphapage_airtouch.com