3D Printed Star Projector

A star projector is simply light going through tiny holes that project small dot on the ceiling hence imitating stars in the dark sky. This is very simple in principle but you can tweak around quite a lot if you're looking for something specific like I do. I tried different existing projects but I wasn't quite satisfied with the results so I decided to come up with my own version.

Here were my criteria :

1. Portable device
2. Position of stars have to be relatively realistic
3. Ability to change and improve position and quality of stars

I didn't reinvent the wheel so I designed and 3d printed a dome and a base.

Star Dome

I found a project on github (thanks to InfernoEmbedded for your work) that was doing precisely what I was looking for. It generates a sphere with holes corresponding to position of stars in the sky. I edited the code for my needs. For example I made the hole diameters the same for all the stars instead of adjusting it depending on the star magnitude. I found out that it was easier this way but nothing prevent me of improving this part later and print a new dome.

Base

The base is straight forward. I needed something to house the wiring and the led light. It has a socket to install a TP4056 and a simple hole to insert a switch.

Electronics

Nothing too fancy. You need a 3.6-3.7V lithium battery along with a TP4056, which is the circuit to charge the battery. You obviously need a led light and I'll give some more explanation about it down below. The hole for the switch is 22mm but I also included an stl file with no hole so you can adapt it to your switch. To get the current at an appropriate value, you'll need a resistor. I use 4.7ohm but you can use whatever is right for you. Remember the good 'ol equation you learned in high school? V = R x I.

What you'll need.

1. 3d printed dome and base (sorry you need a 3d printer or a friend that has one)
2. TP4056 (Amazon)
3. Bright LED (https://www.aliexpress.com/item/33032541683.html)
4. Resistor (4.7ohm)
5. Switch
6. 3.6-3.7V lithium battery (don't use regular AA battery)
7. Battery holder
8. M3 screws

Printing the base and the lid is somewhat easy. You'll need a bit of support for the lid but that's it. For the switch hole I included a file that has no hole so if you have a switch different than mine you can edit the model for your need.

For the dome I suggest you print it with the inner part facing down and with tree support in the middle. Make sure there is no support starting from the outside because it will fill some holes and you'll have a bad time removing the support material. You could print it like a bowl if it's better for you but I rather not because it doesn't look as nice.

Choosing the right LED light was my biggest struggle in this project so I'll give some explanation. I tried using LEDs from led strips. I didn't like the result and found that it wasn't bright enough. I looked for brighter LEDs and bought some on-board LEDs from amazon. That wasn't a success either because the light was too much diffused and this is an important part take into account. If you want well defined bright dot on the ceiling you want something non-diffused. Meaning the light has to come from a tiny single point and be the brighter possible. I finally found the ones listed in the supply list. Minimally diffused and bright enough.

Last point but not the least about LEDs : don't use multiple LEDs. If you do so you'll double, triple, quadruple, the amount of stars. I'll let you figure out why. It was so obvious but my slow brain didn't catch that at first.

Just follow the circuit diagram. The TP4056 is a circuit board that handles the charging of a 3.6-3.7V lithium battery. You plug in a 5V USB-C cable as input voltage. At the other end you have both connections for the battery pack and another set of connections to power up the light itself. Add a switch to it and you have all you need for a portable device.

Here is a suggested soldering sequence the wire it up.

1. Solder the battery pack to the TP4056. Make sure you have the polarity right and that you use the inside connections on the board. You'll see the labels B- and B+.
2. Solder a wire on one polarity of the switch and the resistor on the other polarity. Make sure the wire is a bit longer than you need.
3. Insert the switch in the base.
4. Solder the output voltage wires on the TP4056. Again make sure you have the polarity right and that you have long enough.
5. Install the TP4056 in the socket and screw it to the base using M3 screws.
6. Solder the + output wire from the TP4056 to the resistor on the switch.
7. Pass the wire from the switch and the - output wire from the TP4056 in the hole.
8. Insert the LED in the hole.
9. Cutout and solder both wires to the LED. Be careful to not get it too hot when soldering else you'll make the plastic melt.

I didn't find a good way to stick the LED to the base so I just use some duct tape and it seems to do the trick.

Put the dome on top, switch it on and enjoy the view. If you have kids you'll have great cosmic evenings. :D