Lasercut Decorative Night Light (for Tfcd)

With the glowing sphere decorative night light project you can easily build a lamp yourself to decorate your room! Nonetheless we even provide you tips on how to design your own lamp using the same principle.
Our aim with this project was to find alternative additive manufacturing techniques, that are able to construct multi-material objects. For those projects that do not need high resolution in the vertical axis, this method might be a perfect solution.

Items needed:

• Transparent acrylic glass (make sure it is really Polymethylmethacrylat and not a cheap look-alike material that ruins the laser cutter) [approximately 660x145 mm, 3mm thick]
• Semi-transparent acrylic glass (make sure it is really Polymethylmethacrylat and not a cheap look-alike material that ruins the laser cutter) [approximately 530x70 mm, 3mm thick]
• Plywood sheet, [approximately 280x210, 3mm thick]
• 4 sticks [diameter: 3mm, length: 78 mm; we used metal sticks but any kind of sticks are good]
• LED
• Flip switch
• 3 Volt lithium cell + holder

Tools needed:

• Laser cutter
• Glue
• Soldering iron

All the models and dxf files for laser cutting that you need can be downloaded from Thingiverse from the following link:

http://www.thingiverse.com/thing:1206856

There are 3 dxf-files in total for the different materials you have to use: Outer structure from the transparent acrylic glass Inner structure from the semi-transparent acrylic glass Box from the plywood In these files the elements are already arranged but of course you can easily change their arrangement if you have a different shaped sheet. Just make sure your sheet is big enough for all the elements. For editing these files there are plenty of available programs such as the trial version of CorelDRAW. If you want to build another shape/design (maybe one you found on thingiverse) Autodesk 123D might be a good software. The only thing you should keep in mind is that if you want to use different materials within one layer, you must set an offset to the inner structure. The laser itself has a width and without the offset the parts don’t really stick together properly.

The box is made from two elements, the box itself and the closing mechanism. None if them are too complex but let’s start with the easier one, the mechanism. It is built from the following two elements. You just have to glue part 12 on part 9’s end.
The box is a tiny bit more complex than that, but it is still pretty easy to build. You just have to glue the certain layers on each other in the following order: 1, 2, 3, 4, 5, 6, 7, 8, 10, 11. (Note: Part 1,2,3,4,5,6, 7 and 8 are absolutely the same so you can mix up their order and also you don't have to use all of them, the important thing is to make the box big enough for the batteries.) After that you just have to put the sticks in the holes. When you are ready with the box and the lid you can slide in the lid for finishing the box.

The electronics for this specific project are really simple to build as well. All you need is the battery, the LED, the flip switch and some wires. The following image helps you in understanding the electrical circuit that you need(of course you can also solely solder the components together to make it work).

In our example we use a lithium coin cell (CR2032) with 3 Volt. Due to the forward voltage of our LED (which is about 3.5 V) we do not need a pre resistor for this combination because the LED won’t be “overloaded” with a dangerous current. However, if you want to take other batteries or an LED with a lower forward voltage, you should keep the following in mind.

Especially red and yellow LEDs have a lower forward voltage (usually around 1.7 V). If you use an LED like this it would blow because it will be applied with a current that is too high. To lower the provided voltage you need to attach a pre resistor. Let’s say the power supply provides 3 Volt and the LED has a forward voltage of 1.7 V. That means we “have to get rid of” 1.3 Volt. To calculate the right resistor we use the very famous Ohm’s law. Simply divide 1.3 V by 0.02 A (this is the usual current that single LEDs work with) and you get 65 Ohm. This is the resistance your pre resistor should have.

You should have all the parts and the already assembled socket. Now just layer by layer stack the acrylic parts on it. Stop doing that when you are half way up the sphere because you need to get the LED inside. Solder two wires to the LED and put them through the hole in the acrylic layer. Now solder the cable that is attached to the longer pin of the LED (+) to the flip switch (in our case the pin in the middle). The next wire has to connect one other pin of the switch with the plus pin of the battery holder. Finally the second cable that comes from the LED has to be attached to the minus pin of the battery holder.
Afterwards you need to build the flip switch into the socket. Just mark the width of the hole with a pen and cut out one piece of the layer. Our flip switch it a little higher than the wooden layer so with a sharp knife we had to carve out a little bit more. When the switch fits into the hole you can start to glue the socket together (apart of the closing mechanism of course). Align the LED in the center of the hollow sphere, insert the lithium cell into the holder, close the socket and you are done!