Side Projects

Abacus & Slide Rule vs. Calculator

Modern technology or centuries old instruments.  Which is faster, easier to use, more accurate, and more reliable?  Lets test to find out.

Some classic slide rule, slide cylinder, and slide wheel designs.

Make a slide rule or slide wheel out of paper for free.

Chinese Account abacuses are cheap to make or buy.

You can see the row of 1s called the "earth" above the row of 5s called "heaven".

An HP-15 Business Calculator.  The longest made and best selling calculator of all time.

A classic american slide wheel from 1960.

But who wins in an all out throw-down?


Device / Time Abacus Slide RuleHP-15 Calculator 
Log7:89 0:14 2:41 
Conversion25:3912:54 21:09 

Projection & 3D experiments

Some may have seen my last 3D projector project and this dome project will pick up on where that one left off.  Adding new functionality and enhanced performance, and smaller size.

Current prototype for folding dome screen.

Folding Screen Demo

Needs massive amounts of time and work to complete

Hoberman Spheres are used in everything from space satellites to toys.  One can be used to hold the framework for a collapsible dome projection screen.

The screen tiles fold into pentagon shapes and fold inward with the sphere.

Suspending bars hold the screen to the sphere's outside structure.

The Hoberman sphere can be cut in half and controlled with a bisecting drawstring handle.

Want a Projector light that is both bright and will never burn out?  If you have $500, I have your product.

Lumnix Argon Stret Bulbs

Used in street lamps, signs and signals.

Burn with the 10,000 lumes at 500 watts!  Therefore it needs a big cooling fan.

I have used it with a Fresnel lens LCD projector with great success.

If you can't go big, go small.

Want a projection theater on the go?

Make or build a pico projection kit out of a briefcase.  I have seen around campus and often at meetings and job fairs.  Very useful and lighter than a laptop.

Should you buy a projection system or build it?

posted Mar 12, 2011, 8:33 PM by William Broza   [ updated Sep 16, 2012, 8:20 PM ]

Buying a consumer 3D project costs about $100 per pair of glasses and $1000 for a descent projector.

at 120 Hz and 4000 lumes, are you getting your money?

If you are willing to get your hands dirty with tools, you can do much better.

All you need is a light, LED screen, and two lenses.  One is a focus lens and the other is a flat Fresnel lens.

The Fresnel lens limits the size and resolution of the LED you can use.  But most people can achieve 1080p at 200 Hz using off the shelf parts.

This 1080p 240 Hz 3D projector costs $900 to build and can use cheap polarize glasses or professional shutter image systems.

Half the cost of a pre-made system at twice the quality.

The pentagon tile planetarium hemisphere model can be miniaturized and adjusted to collapse.  This has powerful portable applications.

Take a pattern of equilateral triangles and form a tile dome pattern.  Fold along the bisection line of the triangles to fold the dome flat for easy storage.

This is a mock up of a portable screen.

These are projection hemispheres used to reflect lights on dome screens.

Here is an example of a high performance battery operated projector.  These are ideal projectors for portable dome viewing.

Add two pico projectors to a computer or mobile device to drive polarized or shutter 3D viewing.

Add two pico projectors to a computer or mobile device to drive polarized or shutter 3D viewing.

Many schools and universities have developed methods of building cheap and portable planetarium and immersion projection screens.  These can be made from cheap fabric, plastic, or cardboard.

The simple triangle and pentagon pattern are repeated to build a hemisphere

Hemisphere projection mirrors and DLP computer projection systems are used to drive the image display.

Software must be used to correct for the type of fish-eye image distortion caused by projection on a spherical surface.

For further information, follow this link to the WWT project page.

World Wide Telescope Planetarium