Re: light sources

[Tom Deering <tmd@xxxxxxxxxxx>]

>Reading all these threads has gotten me inspired to build a light box
>for my Saturn viewer. I am wondering if 2 bulbs are needed for adequate
>illumination. That would mean 4 batteries.  In which case I would
>probably go with AA batteries since I would prefer a smallish
>attachment. Or should I check out fluorescent tubes? Is one tube bright
>enough? Should I make it with finger joints? Will AA's burn out too
>fast? Now I'm confused.

I am going to try to answer each of your questions, but the answer 
for all of them begins with "it depends how you design it."  Your 
design will determine how many batteries and what kind, the number 
and placement of the bulbs, etc.   You have to decide what features 
you need or want, and design your viewer to suit those goals.   Some 
design parameters that I have been balancing are:

   Do I want a portable unit, or can I live with AC power?
   What is my weight limit?
   How picky am I about the color of the light?
   How often am I willing to change batteries?
   Physically, how large of a box can I live with.
   Do I need variable light intensity?
   Does the unit need to be rechargeable?
   Do I have the needed construction skills?
   Do I have the necessary electronic skills?
   What is my budget?

Each answer may potentially conflict with another answer.  For 
instance, weight and battery life are at cross purposes.  Since you 
define the parameters, only you can say what design will fit them. 
Having said that, here is an attempt to answer your questions, from 
my point of view.

>I am wondering if 2 bulbs are needed for adequate illumination.

Depends on the design.  Geometrically, two bulbs could work pretty 
well, each centered on a film chip.  Or a single tube could work, 
horizontally.  The reflector and diffuser design will spell the 
difference between success and failure.

>That would mean 4 batteries.

Not necessarily.  Depends on your design.  More bulbs will drain the 
batteries faster, that's all.


>In which case I would probably go with AA batteries since I would
>prefer a smallish attachment.

That's my plan, but you may have different tastes than me. If you can 
live with a wire going to an AC outlet, then weight and battery life 
are no longer limiting factors.

>Or should I check out fluorescent tubes?

A regular flourescent tube might be too long, depending on your 
enclosure.  But it's a cheap and efficient choice if you don't mind a 
bigger housing.  The "cold cathode" tubes Richard mentioned are 
smaller.  As long as you can make the electronics work, seem like a 
nice alternative.

>Is one tube bright enough?

Depends on the tube, and how bright you like your slides.  Halogens 
can be dimmed easier than florescents, although neither like it much.

>Should I make it with finger joints?

Not unless you have a lot of patience.  :^)  They are strong and 
pretty, but simpler tabs work fine, and would match your Saturn 
viewer better.

>Will AA's burn out too fast?

Depends on what you consider "too fast".  Four "C" cells will last a 
long time if you have strong arms.  They weigh a lot, but are much 
cheaper in the long run.  How about a "steal the light" design? 
Alkalines vs  NiCads vs NiMH vs lithium. . .

Hope this helps.  I welcome alternative opinions.

Warmly,

Tom Deering