Animatronic Halloween Pumpkins

Animatronic Halloween pumpkins that feature sound and light effects and an animatronic eye to make it even more spooky.

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Every year, for Halloween, my neighborhood hosts a jack o'lantern exhibition. The kids living in the area and their parents carve pumpkins and display them at the neighborhood square. I participate in this event by taking my pumpkins to another level and making them their own animatronics show. It brings me tremendous joy to see how many people enjoy seeing the pumpkins sing and light up.

My project is a set of three animatronic Halloween pumpkins that feature sound and light effects and an animatronic eye to make it even more spooky. The electronics are embedded into real carved pumpkins to make them realistic. The whole device is controlled with a custom Android application that communicates via Bluetooth with the electronics hosted in the main pumpkin.

The pumpkin firmware is developed in C using the Arduino framework. The development environment is  VS Code with the PlartformIO extension. The Android app was developed using a Skratch-like programming language developed by MIT called MIT App Inventor. The hardware is built around a Teensy 3.5 development board which features an ARM Cortex-M4 at 120 MHz. All the electronics are mounted on a carefully routed protoboard.

The sections below present a list of this project´s features.

     Audio Effects
* Audio files are stored in an SD card. The audio files consist of several Halloween-related songs and spooky sound effects. The files are 16-bit PCM (Pulse Code Modulation) at 44100 Hz .wav files.
     Light Effects
* Two LED strips: one for the main pumpkin and another one for the three smaller pumpkins
* When not playing an audio file, the LED strips display simulates candles lit inside the pumpkins.
* Light effect 1: When playing an audio file, the LED strips can display the LED brightness synced to the audio file that is playing. This effect is displayed in different color versions: white, red, green, and purple.
* Light effect 2: When playing an audio file, the LED strips flash on and off with three different colors at a rate of 60 ms. This effect is displayed in two versions: red-green-blue and purple-green-orange.
* Light effect 3: When playing an audio file, the LED strips display a rainbow color effect that cycles through the color wheel in 5 seconds.
* Light effect 4: This is a specified light effect designed for the audio file MountainKing.

     Animatronic Eye
* The animatronic eye features two servo motors, one for the eyelid and one for the eyeball.
* The code for both motors allows for an organic movement where the servos reduce their speed as they approach the new position.     


* The communication between the pumpkin and the Android app happens via Bluetooth. During standard operation, the app transmits 6 values in a string, the Bluetooth module on the pumpkin receives it and passes the string to the microcontroller via serial communication.
* When a Bluetooth connection is established, the pumpkin transmits the name of the audio files stored in the SD card to the app which stores it in a list. That way the audio files can be changed without modifying the code.
* When the volume is changed on the app, the pumpkin sends the volume value to confirm to the user the actual volume.


Pumpkin electronics block diagram

Portable Network Graphics (PNG) - 41.27 kB - 10/29/2023 at 20:36


  • 1 × Teensy 3.5
  • 1 × XL6009E1 Bost Converter module
  • 1 × 3 Inch Speaker, 8 Ohm, 20W
  • 1 × TDA8932 35W Digital Amplifier
  • 1 × Bluetooth module HC-06

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  • 1
    General Instructions

    The project file in the GitHub repo has images of the project, a block diagram of the hardware, and more detailed descriptions of the software. 

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