What's this all about?

LED is very often used in various projects. There are many types with various colours, shapes, sizes. But what if none meets requirements for your project? Maybe some custom made acrylic addon would help you out.

This page presents a simple project showing how to easily "bend" a light stream using basic optics rules.

Physics

In short: each substance has its own specific abilities to transport light. When two substances of different refractive indexes meet on light's way - the light changes its route by some angle. This can be used to "trap" stream of light and guide it in some specific direction. Just heat up the plexiglass and change its shape any way you want. New shape will be the route for light beams emitted into it. Cool, huh?

If you want to get more about it, good starting point is wikipedia's site on refractive index (http://en.wikipedia.org/wiki/Refractive_index).

Application

What will it do?

HDD can be slow throat of a computer system. This is why most of PC's have HDD LED indicating hard drive's work, to notify the user of the reason why his machine might have feel slower at some moment. It's a nice feature, but in my case - I am having my PC box under the desk, so I don't see the LED on my box' front panel. I've decided to install the HDD LED above the worktop - on the LCD. I am far from permanent tune ups and I am sure glued LED wouldn't look any good. I've decided to hide the LED behind the LCD and just bend the LED's light stream to the front. I am using plexiglass for that purpose.

What one needs to do it?

Whole set of incredients I've used for this one is visible on 'figure 2':

pieces of plexiglass
saw
sandpaper
hot air station
dremel
drill
polishing tip
LED
tweezers

How to make it?

Plexiglass comes as board, so first we have to cut desired shape out of it, but read about bending before you actualy cut it. Then we need to set the hot air station to about 200C degrees and heat up the board right in place where it is going to be bent. Plexiglass isn't a conductor, so it heats up very slowly. It may take even few minutes to properly heat it up. Plus of it is, that it also cools down slowly, so we'll have like half of minute to set the desired shape. Every touch leaves some mark on hot surface. Permanently! This is why you may want to cut coarse shape first and then cut it precicely after bending. During the long time of heating up, the heat spreads fairly within whole element, so be carefull when you touch it! After it's bent and cut, good idea is to even the visible surface. I've used sandpaper "80" first, then water sandpaper 800, and then I've put the polishing tip to my dremel. Be carefull not to melt the board while polishing - I've set my dremel to slowest possible speed. After this, the surface is all shiny and nice. On the other end of our light's guide we have to drill a hole to fit the LED in. Same as before - watch out with speed/heat during drilling. I'm using 3mm LED and 5mm plexiglass, so it's easy peasy. I overdid with the drilling here, so to shring the hole's diameter I had to first warm up the hole and then squeeze the board with tweezers a bit. When it cooled down, LED fit it perfectly.

All this is very simple. pics below show whole procedure.