Simple Animatronic Skull

If you have been following our blog, you have seen some fun and scary Halloween projects posted by my coworkers here at Pololu, so I thought that I would share the first part of the prop for my costume this year. After watching an animatronic devil baby terrorize New York City, I knew I wanted to build a similar demon baby that would be attached to me with a baby carrier.

Implementation

After finding a small skull at a local Halloween store (for 4 bucks!), I was ready to throw some servos into it. Using hot glue, I attached two HD-1705MG high-speed mini servos, one for the jaw motion and one for the neck motion. I also decided to add two 8mm addressable RGB LEDs into the eye sockets of the skull. For controlling the servos and LEDs, I used an A-Star 32U4 Mini SV. The LEDs are powered by the A-Star’s 5V output, which is regulated by the onboard switching regulator. With the Arduino Servo library and our Arduino library for WS281x-Based Addressable RGB LEDs, I was able to get this skull animated quickly. Below is a GIF that shows the skull in action and the program I used for the demo:

Simple animatronic skull laughing.

#include <Servo.h> 
#include <PololuLedStrip.h>

// Create an ledStrip object
PololuLedStrip<12> ledStrip;

// Create a buffer for holding 2 colors for the eyes.
#define LED_COUNT 2
rgb_color colors[LED_COUNT];

// Create servo objects to control neck and jaw servos 
Servo neck;  
Servo jaw; 



void setup() 
{ 
  delay(500);

  // attaches the servo on pin 2 and 3 for neck and jaw.
  neck.attach(2);   
  jaw.attach(3);

  // set eyes red
  colors[0] = (rgb_color){ 30, 0, 0   };
  colors[1] = (rgb_color){ 30, 0, 0   };

  ledStrip.write(colors, LED_COUNT);  
} 


void loop() 
{ 
  // move neck 180 degrees and laugh
  neck.writeMicroseconds(400);              
  jaw.writeMicroseconds(1200);
  delay(400); 
  jaw.writeMicroseconds(1400);
  delay(100); 
  jaw.writeMicroseconds(1200);
  delay(100); 
  jaw.writeMicroseconds(1400);
  delay(100); 
  jaw.writeMicroseconds(1200);
  delay(1000); 
  
  // move neck back 180 degrees and glow eyes
  neck.writeMicroseconds(2200);             
  for(int i = 30; i < 60; i++)
  {
    colors[0] = (rgb_color){ i, 0, 0 };
    colors[1] = (rgb_color){ i, 0, 0 };
    ledStrip.write(colors, LED_COUNT); 
    delay(20);
  }
  for(int i = 60; i > 0; i--)
  {
    colors[0] = (rgb_color){ i, 0, 0 };
    colors[1] = (rgb_color){ i, 0, 0 };
    ledStrip.write(colors, LED_COUNT); 
    delay(20);
  }
  for(int i = 0; i < 30; i++)
  {
    colors[0] = (rgb_color){ i, 0, 0 };
    colors[1] = (rgb_color){ i, 0, 0 };
    ledStrip.write(colors, LED_COUNT); 
    delay(20);
  }
} 

Complete parts list

• A-Star 32U4 Mini SV
• Power HD High-Speed Mini Servo HD-1705MG
• Addressable Through-Hole 8mm RGB LED with Diffused Lens, WS2811 Driver
• Premium Jumper Wire 50-Piece Rainbow Assortment M-M 3″
• Pololu Stamped Aluminum L-Bracket for NEMA 17 Stepper Motors (This is temporary; I will be attaching the head to a doll in the near future.)
• Battery pack
• Skull with hinged jaw

Looking forward

Like I mentioned earlier, the goal is to make a full animatronic baby that I would carry around with me so I can scare unsuspecting people (maybe I’ll go for a nice walk down the Las Vegas Strip). Look for an update soon.

Related products

	A-Star 32U4 Mini SV (ac02c)
	Power HD High-Speed Mini Servo HD-1705MG
	Addressable Through-Hole 8mm RGB LED with Diffused Lens, WS2811 Driver (10-Pack)