My daughter loves My Little Pony and the offshoot Equestria Girls. She is six. For her seventh birthday she wanted an Equestria Girls birthday cake. So I used my laser cutter to engrave some acrylic with the image, 3D printed a base, soldered some LEDs, and attached a 3D printed battery holder. Made a nice cake topper which was a big hit at her party. Did not have the time to try and use an embedded laser instead of LEDs
Step 1: Image and Engraving
I located a coloring book image of Pinkie Pie as an Equestria girl. I then used my laser cutter to engrave, then cut our, a 5X3 piece of acrylic. The process took some time but I finally got a good result (after a few failed attempts).
Step 2: First base
I first tried converting a plastic project box (2X3) to house the LEDs and battery. However, it looked too . .. well.. crappy. So I turned to my 3D printer
Step 3: LED stand and battery holder
Thank goodness for Thingiverse. The elements would not have been too hard to do myself, but utilizing the sharing on Thingiverse made my project much easier.
Not sure I did it correctly, but I attempted to upload the .STL files of the LED base and battery compartment I used.plexi_led_sign_stand.stl
Step 4: Basic Parts
I did not take a picture of the LED stand before I painted it, so sorry about that. But I included the stl file image to see. I had to paint the inside black, else the lights would shine right through the ABS. That's what I get for using white plastic. Anyway, I pained the outside pink, but did not paint the battery casing. In retrospect I probably should have but hey, live and learn.
For the battery I used a 16340 1200mAh Ultrafire battery. I used that instead of the coin batteries because I needed the mAh for multiple LEDs. I toyed with the idea of just attaching to a transformer, but since it's suppose to sit on top of a cake I decided that was not the brightest idea (no pun intended). I used just regular screws on each end of the battery casing to connect to the wiring. That way I could remove the battery when not in use.
Step 5: LEDs
I then soldered 5 LEDs together. The resistor's I tried early on kept getting too hot. After doing some math I realized I did not really need a resistor given the number of LEDs on the battery and my intend was not to have it on the cake very long anyway. I placed them into the casing and connected the battery. It all seemed to be working just fine.
Step 6: Pinkie Lives
The effect was not as spectacular as I imagined in my head, but then it never is. I think my head is more skilled than my hands at actually creating stuff like this. But my girl is turning 7, surrounded by a bunch of other 7 year olds and a few 10 year olds and they all thought is was really cool. A few of the parents did too. I think the best compliment I had was from a mother who asked her daughter "do you think Daddy could have made that" and the daughter said "no way" then the mother turned to me and said "my husbands an engineer. He would have been impressed, but probably could not have done that." However, while serving the cake, the table was bumped enough that the battery kept wiggling loose and the LEDs would turn off. Probably should have used the transformer after all.