Step 1: Materials
A Parallax USB Servo Controller is the interface between the computer and the servo motors.
Visual Show Automation runs the show & tells the servo controller what to do.
The servo controller circuitry is powered via USB, but requires an external power supply to run the servos.
Audacity can be used to record & edit the sound track.
Step 2: Modifing the Skull Character
Step 3: Making the Talking Pumpkin Character
Cut the pumpkin in half, with a zigzag in the front for the teeth.
Use a straight cut in the back so that there's no interference when the top moves.
Hollow out space for the servo & bracket.
The top is fastened to the servo horn with a piece of aluminum bent into an L shape.
Paint any visible cut surfaces of the styrofoam with a water-based paint (that won't eat away the foam)
Step 4: Creating the Audio
If you're going to have more than one character talking, or add sound effects, make sure to keep the voice tracks separate -- more on this later.
In this case, we've got two voice tracks (skull & pumpkin). Export each voice track as it's own wav file, and a third file containing both tracks.
Step 5: Starting to Tie It All Together
Connect a 5 volt power supply to the servo controller. Look here on Instructables for directions on how to convert an ATX computer supply to a bench-top power supply.
Step 6: The Controller Software
First thing is VSA configuration. The Tools/Settings menu brings up a dialog box listing the configurations for all tracks. Change the type to "Parallax Servo" & set the port number. Change the address to match the channel that the servo is plugged into on the Parallax board. You can give a descriptive label to the track, like Eyes, Jaw, etc. Check the baud rate under Port Settings & make sure it's 38400 for the Parallax board.
The +Value, -Value, & Default set the limits of the servo, and the default starting postition.
VSA has a useful tool called "WaveMotion Analysis" that can automatically generate events from the volume of an audio file (This is why we saved each voice in it's own wav file). Load each voice track & generate control events for the appropriate servo.
Afterwards, load the combined audio track.
Step 7: Setting the Stage & the Final Product
The final result can be seen on YouTube:
Step 8: What's Next?
Add another servo to both the skull & pumpkin so that they can turn.
Have multiple pumpkins that talk togethers. (What do you call a group of pumpkins -- a patch?)
Servos are controled via pulse width modulation (PWM). It might be possible to control LED brightness via the servo control channels of the Parallax board. Add glowing eyes to the skull.
Thanks for looking, and Happy Halloween!