One of my favorite things about xkcd is the combination of the highly technical and highly emotional, as emphasized in comics like Angular Momentum
or The Glass Necklace
. I recently completed a similar project that I thought the community might be interested in.
My brother recently got married, and as a wedding gift, I decided to make something along the lines of the Glass Necklace--technical yet very personal. I took the basic idea from Evil Mad Scientist's edge lit cards
, where you scratch acrylic and use an LED on the edge. The light will reflect internally, highlighting the scratches. You can get multiple colors by using multiple layers.
To make this a uniquely personal gift, I used Stellarium and set the time forward to the date of the wedding and estimated the time they'd be saying "I do". This would be the middle of the afternoon, so you couldn't actually see the stars, of course, but it represents where they would be if you could.
I wanted to get Orion and the Pleiades in the shot, and found I was in luck:
The Moon, Mars, and Venus are all lined up together.
I created the above by taking a screenshot of Stellarium and then using Gimp to fill in a (mostly) white backdrop so it wouldn't use too much printer ink.
I then printed this out and marked the magnitude of the stars:
Next, I needed to get pieces of acrylic down to size, which is done by taking a sharp knife, scoring a line several times, and then breaking the peice over an edge. There are tools built specifically for the job, but a good x-acto knife works, too.
I then choose some drill bits, using larger bits to represent brighter stars. Then I simply put the image underneath the acrylic and drilled at the location of the stars:
The holes at the bottom are where the LEDs will go. These need to be made with a drill bit specifically made for acrylic. Acrylic bits have a much more sharply angled point than wood bits. Trying to drill all the way through with a wood bit will often crack the acrylic. I did use wood bits to make the stars; just go slow and it should be fine.
I took some artistic license with the Pleiades and the relative size of the Moon. The Pleiades are simply a bunch of closely-drilled points. For the Moon, I traced the inside hole of a CD with a x-acto knife, then scratched one side with a metal file to give it a shaded effect. (High-grit sandpaper should work, too.)
Next, I traced the constellations with an x-acto knife, scoring several times to get a deep scratch. Result:
Note that the holes for the LEDs in layers next to each other can't line up, or else light from one will leak into the other.
Red light was used for the constellation layer, and blue for the stars. For power, I took an old cellphone charger and cut the end to get the wires. All such AC adapters should list their voltage/amperage. Then you need to know the forward voltage and current of your LEDs in order to calculate the current limiting resistor value so you don't blow them out. An LED calculator
is handy here. It's OK to make the resistor a little higher; they'll just be a bit dimmer.
Result is below. Apologies that it's a bit blurry. I don't have a very steady hand, and didn't have a tripod handy to take a picture with such a highly contrasted light source.
Last part was to build a frame. I used larger piece of acrylic with black construction paper over it for the backdrop. Then two pieces of cardboard were cut with a square section in the middle for the acrylic to fit. The lower piece had a notch cut through one part to put the power cord through. Lastly, another piece of black construction paper was put over to hide the wiring and edges of the acrylic.
I'm overall pleased with how the project turned out (and the newlyweds seemed to be, too). A possible improvement would be to use a PWM channel on a microcontroller to vary the dim on the blue LEDs to give a twinkling effect, but unfortunately I ran out of time before I could get far with that. You'd also end up twinkling the planets along with the stars, which could be solved by using a third layer, or just put it down to artistic license
I do not agree with the beer you drink, but will defend to the death your right to drink it