Toy Story Alien Light Up Headband

Here’s the last part of the Toy Story Alien outfit that I wanted to share — the light up headband! I had actually wanted to make this for San Diego Comic Con, but with all the other stuff I was doing at that time, I just couldn’t get it started, let alone done. But the Disney races were where it really shined anyways since they are so early they’re mostly in the dark so the LEDs looked great.

This is one of my more involved technical projects to date. The modeling was its own beast and I learned so many new techniques working on this. Everything from joining and subtracting shapes to revolved profiles and patterns to hinges and snaps and more. Then there were the electronics. These were actually pretty simple/straightforward as electronics go, but as opposed to putting electronics into fabric, the plastic doesn’t bend in the same way. Figuring out light diffusion. Making sure it would last the whole race and making sure I could tweak it mid-race if needed. Soldering without melting the plastic. So, yeah, lots of pieces.

But look how good they look! Totally worth it!

Let’s start with the modeling. I do my 3D modeling in Autodesk Fusion 360. At this point, I’m comfortable with it, but still sooo much to learn — as this project showed, but I can do the basics pretty easily. We don’t have a multicolor printer (it’s a Prusa i3 MK3S+) so I knew I was going to break up the eye balls, the pupils and rest of the headband into separate pieces for printing in different colors. I also knew I wanted the eye balls hallow for the electronics. I had done a headband before for the Minnie Mouse debacle and the fashion Snowths so I had that to start from. But I did the grippers on the inside better this time, in a way that didn’t slow everything down to a crawl by having a ton of extra bodies.

I realized that I was going to print it laying flat with the eyes facing up and that I didn’t like the way the antenna printed so that become a separate piece that was printed so I could print it up right. I did lots of small test prints for each part so that I could iterate quickly.

I also realized that I wanted to be able to get in the back, so then I had to learn how to make a latch door. More test prints (above was an early iteration that wasn’t ideal as it was hard to get into).

Not all the test prints went well. I have no idea how the printer managed to achieve this. It was both impressive and kinda gross.

But finally it started to look like something.

There were test prints of the eyeballs as well. You might think, oh, that’s such a simple shape. But I ended up having to print it at just a single layer so that you could see the LED glow through it. You do get the seam on the side which I didn’t love, but there was no way around it. I even tried printing them by themselves thinking it was an artifact of printing multiples at once, but, nope. Still there. You can’t print it in vase mode because of the supports, but it was fine for a race. At some point maybe I’ll get a resin printer and that would be the right way to do this one to look cleaner.

But finally it was time to print the real thing. I used this Geeetech apple green filament from Amazon mostly because it was the closest color to our stockings and gloves. I printed everything at 0.15mm quality level. The big guys took almost 10 hours. The little ones were much faster obviously.

Above are all the pieces I printed with a few extras just in case. One thing I realized was I needed some way to keep the LEDs where I wanted them. Thus I had the settings which are the X shaped pieces for inside the eyes and the little hat shaped ones (upper left of the photo) which goes in the top of the antenna.

Next it was time to start putting things together.

But before we do that, let’s just do a quick test of the actual circuit. Yay! It works! Up until this point, I had just held the LED legs on either side of a coin cell battery.

Now you may notice the little coin cell battery holder I have there. The black hockey puck. It holds 2 CR2032 coin cell batteries and then I can nicely solder the wires. Makes it easy to change batteries. Even has a switch attached to it. Well . . . I forgot to take the size of the holder into account when making my back hatch and it was too big. Sigh. So those will be saved for another project. I’ll show you later what I ended up doing. It’s a hack, but for a race, it worked. If I were updating this, I’d look for a button cell batter holder to get in there.

For those who care, here’s a circuit diagram:

The LEDs I used run on 3V at 20mA. Each CR2032 is a little over 3V and has about 225 mAh. This means with 1 battery that 4 LEDs in parallel would last 225/(20 * 4) = 2.8 which is almost 3 hours. However, with LEDs, as the power gets less they will get dimmer and I wanted them to stay bright for the whole race including the almost hour we have before even starting the race.

Instead I stacked 2 batteries in series creating a 6V battery which meant that I would need to create a 6V load. This was easily done by running 2 LEDs in series as well. Now instead of 1 battery and 4 LEDs in parallel, I wired 2 LEDs in series, in parallel with 2 other LEDs in series. Now the calculation was (2*225)/(2*20*2) = 5.6 hours which was plenty of time.

There are definitely other ways to arrange the LEDs and batteries. I could have done fancier things like adding a switch (I tried, but, battery holder fail). But this was sufficient and cheap for my needs. Again, I might go fancier if I were going to make these again. Maybe. I’m also lazy and might just print them exactly the same and then do the same hack since I’d inevitably leave it to the last minute.

Anyhow, now that I knew the circuit worked, it was time to put it together.

Now despite the fact that I had made a little access panel in the back, I didn’t account for the fact that I’d need to thread the LED wires through their holders before gluing everything together. So this meant soldering and then gluing. This was challenging to say the least. It was nerve wracking to make sure I didn’t accidentally melt the plastic because I didn’t really have time to reprint it (nor did I have the mental stamina to at this point). But I got it done.

There was one little piece that did get a little melted, but it was inside, so you couldn’t really tell.

Once all the soldering was done, it was just gluing everything together with crazy glue which works surprisingly well on PLA.

One thing I don’t have a lot of photos of was the diffusion for the LED light. I noticed the the LED was very harsh in the eye balls (and the antenna). So I used just a very little bit of polyfill stuffing inside each eyeball and in the antenna as you can see above. This was just enough to diffuse the light and give it a much more even glow.

Now it was just time to test it all.

And it works!

You’ll notice that I’m holding the batteries together up above.

It was about this time I realized that the battery holder wouldn’t actually fit in. So what I ended up doing was bringing some electrical tape with me and just taping the batteries securely to the ends.

At one point during the race I think I did have to retape someone’s batteries because they were flickering but it was fine after that. Is it elegant? Nah. But could anyone tell? Also, nah 🙂