LEDs or Halogens?

[Whytech]

A couple days is not much time!

Well, if you have access to perspex rod or even layered sheets you might be
able to create a light pipe from it. Just keep the bend diameters large-ish.
You should be able to pump light down 4-5 stacked layers, bent appropriately

If you don't mind a throw-away item what about hobby casting resin - you
could cast the whole damn light in clear resin for 10-20 bucks. With care it
should be just about immersible then...?

(watch out for movement while the resin sets. Things can become unconnected
so solder everything that moves)

-Andrew

Whytech
MSP430 / PIC / AVR tools, SMD prototyping adaptors
Imagecraft MSP430 C compilers
http://www.whytech.com.au


"Russ" <russell@thehovel.net> wrote in message
news:bjf8e4$gjhnl$1@ID-192123.news.uni-berlin.de...

"Whytech" <thru_website> wrote in message
news:3f5afd05$0$23615$5a62ac22@freenews.iinet.net.au...
I think you'll find the most flexible solution is large diameter fibre
optics. They are available in most countries from specialist suppliers
(try
google). Some of these fibres are >1" round and can transmit a lot of
light.
You can
a) keep electronics away from water
b) reduce conducted heat from melting the ice
c) cut down on infrared by filtering before entry to the fibre
d) mix colours, intensities etc.

cool eh?

Very true, however there is the issue of time and budget!

I've been experimenting with a 15w halogen bulb, but despite the fact that
the heat generated shouldn't be an issue due to the sheer volume of ice,
and
that having water in the tray isn't really a problem, it starts to get
tricky when you consider some risks. If I totally enclose the bulb in a
glass test-tube, it may still get inadvertently shattered, if I encase it
in
perspex tube, it may become exposed and without the cooling of water/ice,
the tube will promptly melt (as I discovered). Also, inside glass, if any
water gets in and the unit is exposed, the water will boil and there is a
risk of explosion...

Given the time constraint (next few days) I think I will try a
cold-cathode
tube of the Jaycar variety, inside a sealed perspex tube with
well-insulated
cabling. That said, even in a few inches of water, it is surprisingly hard
to get a guaranteed watertight seal using silicone.

Thanks for all the suggestions.

Russ.

 

[Brian Goldsmith]

"Whytech" <thru_website> wrote

A couple days is not much time!

***It is, considering that the OP wrote his message before the 4/9/03
not the 7/9/03.
Brian Goldsmith.

 

[Russ]

"Brian Goldsmith" <brian.goldsmith@nospamecho1.com.au> wrote in message
news:Ksj7b.90982$bo1.15134@news-server.bigpond.net.au...

"Whytech" <thru_website> wrote

A couple days is not much time!

***It is, considering that the OP wrote his message before the 4/9/03
not the 7/9/03.
Brian Goldsmith.

It's a favour for a friend, and its a one-off for an art installation - a
room full of huge blocks of ice. They are going to have a tray (a huge one
used for photography) of ice with drinks and glasses sitting in it. I made
the mistake of suggesting it would be nice to light up the ice from within.

Being unpaid, but wanting to do something decent, I was looking for a
solution that I had at hand, or something I could recycle for other uses - I
had plenty of halogen lamps, and blue LEDs would come in handy down the
track.

I'm grateful for the advice and opinions given by people in the group - it's
certainly added to my understanding of different light sources, and I'm sure
I'll use this knowledge down the track at some point.

As it turns out, I'd forgotten that I had got a few Sharp panels for laptops
from Oatley a while back, along with inverter kits which I'd been planning
to convert to little light tables for looking at film negs and trannies.
These panels have a 150mm cold cathode tube which is easily removable.

I've siliconed one in perspex tube and depth tested it to a few metres
(swimming pool = test tank) to make sure it's water-tight. I'll wrap some
blue gel around it and hopefully 2 of them will put out enough light -
they're rated at 4w, although the Oatley inverter draws about 600ma at 12v .

Many of the suggestions were both innovative and interesting, and I probably
would never have discovered the range of possibilities had I not asked the
question.

Russ.