Skull tracking skeleton

I decided to make the Motion Tracking Skull Halloween prop posted by Brandon on 7 Oct 2014. I am not going to reiterate everything he said, so please read his work first. … oween-prop
I purchased everything he listed except for the servo ( I had several of these). So I went to work finding a skull. Well I had a full size skeleton so I cut the head off thinking that this would work fine.
I had to then educate myself on the program syntax and figure out what his program was doing.
I made several changes to his setup:

  1. I changed the servo to channel 1
  2. I changed the 1st analog input to channel 3
  3. I changed the 2nd analog input to channel 5
    This made it a lot easier for my large fingers to get in and move the pins.
    I downloaded the analog sensor characteristics (5V operation) that he used and found that the sensitive part of the sensor is between 4 inches and 20 inches. You do get a reading at 60 inches but it is less than a volt. Any noise (i.e. outside light etc) will make it difficult to identify a difference between the two sensors.
    I took his program and modified it making the appropriate changes as listed above. I also decided that it was impolite to stare, so I put in a timer that takes the head back to center. In retrospect I would add a little more time to this as it follows you and then quickly looks away (my wife thinks this is creepy).
    Here is his adulterated program:

8000 #sets the initial timer (should have made this 9000) 6000 #sets initial (middle) position of servo dup 1 servo #initialize servo on channel 1 6000 delay #delay to set up begin #take the difference between two analog signals 3 get_position 5 get position minus dup -140 less_than if swap dup 3600 greater_than if 5 minus swap endif endif 140 greater_than if dup 8800 less_than if 5 plus endif endif dup 1 servo #updates servo position #this is where I added the counter swap 1 minus dup 1 greater_than if #checks to see if the countdown has reached 0 swap else drop drop goto quack #drop clears the register and goes up to quack endif repeat

Now that I had the program working I started modifying the head. Since I was putting it on the skeleton frame it needed to be light. I cut a square hole in the base of the skull (where I chopped of the head) and installed the servo. I tried a battery pack stuffed in the head but the skeleton spine didn’t like the weight, so I opted for a 6V lantern battery that had enough mAh to get through 30 days. I hid this behind the skeleton, running the wire up the skeleton spine.

I had a piece of proto board which fit the sensors perfectly. I found a piece of thin plastic and made a template for the inside of the jaw. I took a screw two nuts a washer and a T-nut screwing the T-nut to the bottom, then a nut up towards the top then the washer then the plastic then the proto board then the nut right at the top.

I put this in the jaw of the skeleton head, put some painters tape around the front edge so it wouldn’t make a mess and foamed it in place. Use the foam sparingly- mine kept expanding for a day and a half and slightly warped the plastic. In retrospect I would have put more holes in the plastic for the foam to ooze out of. When it finally stopped expanding it hardened. The T-nut at the bottom held the screw in place so I could remove the proto board and start connecting parts.

I had to screw a connector plate to the servo on the skull and then screw the connector plate to the spine of the skeleton. A bit tricky.
I soldered the premium jumper wire (I used male to female) to the proto board, ran the wires to the Micro Maestro, connected the sensors, connected the battery and everything worked. I found that the range was shorter than I thought and realized that the sensors were reading part of the bottom of the skull jaw. I removed the proto board, drilled a new hole that allowed the sensors to sit lower.
This hard working skeleton is at the Cedar Gables Inn Bed and Breakfast in Napa and has a lot of fun scaring our guests.


Awesome project! We are really excited to see people implementing our Halloween example projects into a grander setup. Since you were unable to upload your GIF, can you try uploading it to a free image hosting site (e.g. Photobucket) and post a link to that? If that does not work, you can try emailing the GIF to us (at

Also, if you have any additional pictures, video, or documentation to share, we would love to see it!

- Amanda