This ghost is powered by 2 sets of 4 AA batteries (6V). It uses two microcontrollers, one ARM on a Teensy 3.1 board and one ATmega on an Arduino Pro Mini clone. The reason for this is I failed to run the servos in parallel with audio on the Teensy board. Maybe they require the same hardware resources. As I didn't have time to dig into the issue (halloween is tomorrow), I got a cheap arduino clone board I had in my drawer.

The Teensy 3.1 board is responsible for:

• running the ultrasonic sensor checking the distance of it's victime,
• playing scary sounds,
• enabling and disabling hand and eye animation on the other microcontroller.

The Arduino board handles hand waving and I glowing. I tried to make the code asynchronous, so the animations look nice, however I think more work should be done on hand waving.

When the Teensy board detects someone within 30cm range, it plays a WAV file from the SD card and activates the Arduino. The audio file to play is chosen randomly.

Arduino part is activated when it reads '1' on it's serial port and deactivated when reads '0'.

Most components are connected directly without any additional circuitry or components (with one exception for capacitors at the output of Teensy DAC, as noted in the documentation), so I don't think a schematic is needed. If you would like me to post one after all, write it in comment section.

Here you can see it in action:

Yes, my workshop desk is less than 1 meter long...

And again, in the dark: