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Re: [APD] LED Lighting

he he  The bulbs don't mind being emersed sub the leads on
them tend to be fussy. All Electrically conductive parts
must be insulated and waterproofed before bringing near

I know that Wright is well aware of this, but at the
mention of putting LEDs in water, I thought it deserved

As for control. Specs are usually given for voltage ranges
-- control the ammps or the voltage but either way, don't
overjuice them (tech term) or they'll say bye bye quickly. 

Wright do you really think transistors are needed in a
power supply? Low voltage DC, a rectifier and some
resistors ought to do the job. But with enough to light a
tank, even the resistors would be redundant, no?

Scott H.

--- Wright Huntley <whuntley at verizon_net> wrote:
> Andy and Scott,
> > Message: 2
> > Date: Mon, 29 Dec 2003 09:17:15 -0800 (PST)
> > From: "S. Hieber" <shieber at yahoo_com>
> > Subject: Re: [APD] LED Lighting
> > To: aquatic plants digest <aquatic-plants at actwin_com>
> > 
> > There's nothing to stop one from using the new super
> bright
> > LEDs for lighting a tank.  There are a varitety of
> color
> > temps to satisfy diff tastes. The problem has been the
> cost
> > of the LEDs and the assembling a suitable array of the
> > devices to light a tank.
> It is a great idea, and gives us an ability that has been
> difficult or 
> impractical with other lighting -- immerse the lamps!
> This will bring a 
> whole new era of illumination design to planted aquaria.
> I have just 
> been coasting along, waiting for prices to drop a bit
> more.
> > 
> > It's not impossible to make such an array, just a pita.
> And
> > if one doesn't get the voltage right, the LEDs burn out
> > very quickly.
> Voltage isn't a good thing to set. The diodes will
> develop a certain 
> voltage for a given current, and current regulation is
> more certain to 
> not overdrive them in most cases. The Wattage and light
> output track 
> current very well, but the voltage is low and is not
> changing very much 
> over a wide range of currents.
> [It is exactly analogous to using a needle valve to
> control the flow 
> rate of CO2 and not a pressure regulator (that allows any
> old flow 
> rate), like an Eheim check valve.]
> > 
> > Try running them at a bit below the rated level. If you
> use
> > diff colors (red, blue, green), then put the diff
> colors on
> > different circuits back to the power supply -- the
> reason
> > is that diff colors heat up and draw current at diff
> rates
> > and the LEDs will tend to last longer if you yu keep
> them
> > separate.
> Again, each kind has its own *current* needs, so for
> crying out loud 
> don't put each on a Voltage-regulated circuit! Drive them
> with the 
> collector of a transistor, and regulate the current
> through them, not 
> the Voltage across them, which varies with doping, temp,
> age and a lot 
> of other non-essential parameters.
> By building the leds into a bar that mounts just below
> the water line 
> along the front of the tank, illumination of plants and
> fish will be 
> easy to control, and many irridescent fish will light up
> unbelievably. 
> Note that the directional design of the LEDs means no
> reflector is 
> probably needed or desired. A diffuser in front of the
> LEDs can be used 
> if more spread is needed, but it will cost efficiency,
> fiercely, I suspect.
> Narrow-beam LEDs are made worse when the beam hits the
> water, as all 
> rays are bent toward the center of the beam, somewhat.
> The surface acts 
> a little like a focussing lens. Immersed, they will
> actually probably 
> spread much wider as the index difference between lens
> and water is much 
> less than the lens-air difference. Surface refraction and
> reflection are 
> no longer the problem they are with hoods in air, and the
> illumination 
> may be really efficient. Heat can be conducted away from
> the LEDs by a 
> simple aluminum heat sink that extends up out of the
> water, if that is 
> needed.
> LEDs typically operate at only a few volts, so the
> insulation needed is 
> just a thin paint of silicone potting compound o/e. [I
> would still 
> provide a good ground on the assembly just in case
> something fails in 
> the power source. That and a GFI could save your fish, or
> your life, 
> even! :-)]

S. Hieber

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