Aperture Science Sentry Turret Costume With Sound and Lights

My son wanted to be a Sentry Turret from Portal this Halloween.

Naturally, I wanted to take it a little further, so I started designing and ended up with this.

Most of the costume is made from thick cardboard, and the "eye" houses some electronics that play voice lines and flash an LED. I used a bare ATtiny85V chip, but there's enough room inside the enclosure for an ATmega328P or perhaps even an Arduino Nano board.

A shoutout to Goth Mom's Portal turret costume, which helped inspire this project!

For the costume

1. Corrugated cardboard (from old moving or shipping boxes)
2. A4 cardstock (300 gsm or similar)
3. Webbing straps
4. Scrap fabric (for padding)
5. Elastic band
6. Black duct tape (~12 mm wide)
7. Black velcro straps
8. Round plastic wall clock (~9 cm diameter, for the eye housing)
9. Plastic tray (used as a mounting plate for the clock)
10. Clear plastic binding cover sheet (150 microns thick; thicker would be better)

For the electronics

1. ATtiny85V or similar microcontroller
2. GD380D-M or similar audio playback module
3. Perfboard
4. 3x AAA or 3x AA battery holder
5. 3x AAA or 3x AA batteres
6. 8R 0.5W speaker
7. Tactile push button
8. SPDT switch
9. BC327 or similar PNP transistor
10. A few resistors
11. A few capacitors
12. Red LED
13. Connectors
14. Solid-core hookup wire (for on-board connections)
15. Stranded hookup wire (for off-board components)
16. Screws and washers

I cut an oval shape out of corrugated cardboard and covered it with white paper. You can also use white cardboard if you have some.

The size depends on the person wearing the costume. I made mine to fit a preschooler.

I found a cheap wall clock at a local store that was perfect for the eye. (If you live in Europe, TEDi has you covered! Not sponsored, by the way.)

After disassembling it, I removed the clock mechanism and the glass front cover, leaving only the plastic outer shell and the backplate.

Then I printed an image of the eye just large enough to fit inside the clock shell, cut it out, and cut a matching circle out of a clear plastic binding cover sheet to make the printed eye a bit sturdier.

The printed eye can then be secured inside the clock shell using a little hot glue.

The clock had a rectangular protrusion on the back, so I cut a matching hole in the cardboard to let it fit through.

I also added a vertical black stripe down the middle using duct tape.

To provide rigid support for mounting the clock, I cut a plastic tray into a roughly rectangular shape and drilled a few holes for the mounting screws.

I made a neck strap out of webbing and added some padding using scrap fabric.

I made two holes in the strap, just large enough for the mounting screws to fit through. I also added washers to prevent the screws from pulling through the strap.

The strap goes around the back of the neck and supports the front of the costume.

We can now assemble what we have so far by sandwiching the main body between the clock and the backplate, attaching the neck strap, and securing everything together with two screws.

(The photo was taken after I had also installed the electronics, so it shows where the battery holder goes. I'll cover the electronics in the second half of the post.)

I made the headpiece out of white cardstock by cutting out a semi-oval shape and adding a vertical black stripe down the middle, matching the body.

I glued two more strips of the same cardstock along the bottom edge to reinforce it before punching two holes for the elastic band. This makes the paper less likely to tear around the holes.

I cut two side panel shapes out of corrugated cardboard and covered them with white paper.

The panels will be attached to the upper arms using Velcro straps, so I cut two small slots in each panel and threaded the straps through them.

I intentionally left the black Velcro straps visible on the outward-facing side. They break up the solid white surface and add a bit of visual detail.

At this point, the costume itself is basically done. If you don't need the electronics, feel free to stop here or add your own sound and light effects however you like.

For the sound and light effects, I designed a circuit with an on/off switch and a button. Pressing the button plays a random voice line and flashes the LED with a brightness that matches the audio volume.

I also wanted to make sure the costume could run on batteries for at least a full day, preferably longer.

For the audio playback module, I chose the GD380D-M. I also considered the DFPlayer, which has a microSD card slot, but the GD380D-M has much lower power consumption.

For the MCU, I determined that the ATtiny85V has enough GPIO pins for all the features I need, while also offering very low power consumption.

The MCU connections are:

1. UART TX – for communicating with the audio playback module
2. LED – for the light effects
3. Button – for user input
4. Transistor – for completely cutting power to the audio playback module when it's not in use
5. Audio signal input from the playback module – for sampling the audio signal with the MCU's ADC and adjusting the LED brightness accordingly

The PCB view shows the layout I used, with thick blue traces representing solder connections and thin colored lines representing jumper wires.

The latest code is available in this GitHub repo.

One interesting detail worth noting here is that the components go on the side of the perfboard facing inward, while the LED goes on the opposite side, facing outward.

I used single-sided perfboard, so I glued a small piece of it to the opposite side of the main board, with the copper pads facing outward. The LED legs pass through both boards and are soldered to the small piece, sandwiching the main board between the LED and the smaller board.

I also reinforced the small piece at four points using short, rigid metal links soldered to both boards. (I used the leads from zero-ohm resistors for this, but any sufficiently stiff, solderable wire should work.)

I used more flexible, stranded wires to connect the switch, button, battery holder, and speaker to the main board via connectors, making it easier to disassemble everything.

In the photo, you can see that I used Blu Tack to hold the wires and speaker in place inside the clock shell. The photo was taken before the final assembly, though, so depending on the exact parts you're using, hot glue, screws, or another mounting method might work better for securing everything.

I intentionally chose alkaline batteries over LiPo batteries, even though a LiPo battery would have easily fit inside the clock shell. LiPo batteries can be dangerous if short-circuited or damaged, so I decided against using one.

Similarly, I decided to keep the battery holder outside the clock shell. Even fitting three AAA batteries inside would have been a fairly tight squeeze, and I was worried about accidentally short-circuiting something.

This also has the added benefit of making battery replacement easier.

Regardless of the battery type, make sure all exposed electrical connections are properly insulated and secured to prevent accidental short circuits.

With the electronics secured inside the clock shell and everything assembled as described, the project is complete!