Animated Star Wars Hat Episode 2: Attack of the Domes (R2D2 Hat!)

Three years ago I published my Death Star Hat instructable, which has been a hit at Dragon Con. I got some great comments on it; one was by user Jayefuu who suggested I build an R2-D2 hat with lights and motion. I thought it was a fantastic idea and I've finally gotten a chance to make it happen, just in time for Dragon Con 2015.

Step 1: Tools and Materials

This was one of those "I made it up as as went" kinds of builds. Several parts were just re-purposed junk. These materials are the core bits:

Two large plastic serving bowls, approximately 10-12 inches in diameter. One should be small enough to fit loosely inside the other. Troll Wal-Mart, the Dollar store, etc. for cheap options here.
a hardhat (specifically, the fitted liner from the hardhat)
a regular hobby servo (avoid the miniature ones -- they're probably not beefy enough)
an Arduino UNO
(12x) 330-ohm resistors
1K-ohm resistor
4 cell AA battery pack (the kind with a built-in switch)
9v battery pack (again, get the kind with a built-in switch)
10mm blue LED
20mm red LED
20mm green LED

Tools were mostly basic woodworking and electronics fare:

drill
utility knife
phillips screwdriver
soldering iron
wire strippers
rotary tool
hot glue gun
disc sander

I did have one piece that was 3D printed -- if you don't have access to a 3D printer you could just paint the outline of the part and still have a good prop.

Step 2: Prepare the Bowls...for Something Greater!

So the general idea here is that one bowl is stationary and fits over your head; in this step's pictures this is the blue bowl. The other (red bowl) will rotate around it and be the "R2 head" we see when all is said and done.

My red bowl had a lip on it that made it look more like a Charlie Chaplain hat than an R2-D2 hat, so I cut that off as shown in the second two pictures. That left a ragged edge, so in the next picture I used blue masking tape to define a ring around the cut lip, giving me a nice even line to sand up to.

Next I mounted a servo on the inner bowl with the shaft aligned with the center of the bowl (or close thereabouts) and mounted a matching servo horn on the outer bowl. The outer bowl was pretty flimsy, so I used a piece of thick plastic on the outside of the bowl to reinforce the servo-horn-to-bowl fastening.

Step 3: Fitting the Hard Hat Liner, or Whereby I Demonstrate the Laziness of Re-use by Reference

Here we attach the hard hat liner to the inner bowl. This step is exactly like one in my Death Star Hat instructable. Instead of messing with perfection, just go over there to get the scoop. Don't worry, I'll still be here when you get back. (While you're out, can you pick up some cookies?)

Step 4: Paint It to Valhalla, All Shiny and Chrome!

I masked off the servo and servo horn with blue tape, then spray-painted the outer bowl blue and the inner bowl black (to make it less visible).

Now for the fun part -- I used blue masking tape on top of the blue paint to define the blue details on R2's dome. I started with bands of tape around the bottom and top edges of the bowl, then sketched in and cut away the details leaving the blue "doors". Then I spray-painted silver on top of all that, so when it was dry I peeled the blue tape off to reveal the blue details underneath.

At some point in this I painted the "radar eye" piece I'd 3D printed and then hot-glued it on as shown in the last picture. That piece can be downloaded from Thingiverse. It'll probably need to be scaled down a bit -- try about 0.61 original size (that's the ratio of an 11-inch bowl to a full-size R2 dome).

Step 5: Light It Up Like the Fourth of July

The dome has three lights, all controlled by the Arduino. I used a 20mm red LED for the front light, a 20mm green LED for the read light, and a 10mm blue LED for the front holoprojector.

R2-D2 purists will mock me for using red instead of blue for the front light and green instead of yellow for the rear light. Relax, y'all. If you made it this far expecting screen-accurate, well, um...yeah. Have a cookie. They're really good. The nice folks from Step 3 got them piping fresh from a locally-sourced organic gluten-free bakery.

I didn't realize it when I bought the 20mm red and green LEDs, but they are each actually six independent LEDs globbed together in a larger blob of plastic. This meant I could control each of the internal LEDs separately to give the whole thing a mottled "sparkle" effect. So I wired them up with that in mind (see the 5th and 6th pictures). I used some scrap telephone-cord wire for most of my cabling here. See one of the pictures for how I saved space by soldering the 330-ohm current-limiting resistors directly to the pin-headers that plug into the Arduino.

The front holoprojector was made from the cap of a squeeze-tube of wood filler that had dried up (see what the caps originally looked like in the last 2 pictures). I often keep caps from containers for purposes like this (for example, caps from toothpaste tubes make excellent "control panel" knobs).

Step 6: Top and Rear Holoprojectors, the Cheapskate Way

Once again, up-cycled caps to the rescue. I spray-painted a couple of WD-40 caps gray and hot-glued them to the appropriate places as shown.

Step 7: Electronic Jibba Jabba

The picture shows the gist of the wiring. For simplicity I just put a single LED in the diagram - repeat as needed to get the red, green, and blue LEDs up and going. I used 330-ohm resistors with the green and red LEDs and a 1K-ohm resistor with the blue LED.

I recommend using the battery holders that have a built-in switch. Doing so gives some extra control over the functions -- you can switch off the head rotation by cutting its power while still having lights (powered through the Arduino). This is particularly useful for taking pictures.

The Arduino code is attached to this step.