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From Animatronic to Android

by Mark Medonis

Maxwell Robot head
Or, just how does Maxwell robot work exactly?

My robot project Maxwell began as an attempt to make a robot that looked like a robot. Also, I was interested in working with the technology used in movie special effects, the technology of animatronics. However, as time has passed Maxwell had gained more robotic features that go beyond movie special effects technology. Combining robotic features with lifelike mechanical motion takes Maxwell from the realm of animatronics into the realm of androids.

Okay, so how does Maxwell work? Maxwell combines several main systems, broken down into two large categories: the joystick control and the PC control.


Joystick Control - Eye and Head Motion

Although the full height of Maxwell is 4 feet 6 inches, most people look at his face. This is not surprising, as most people look at the face of other people as a main avenue of communication.

The head of Maxwell has five servo motors inside. Two servos move the eyes, two servos move the head, and one servo moves the jaw. The jaw movement is controlled by the PC, which I will describer further in the PC control section. The joysticks move the eyes and head, four servos total.

What's a servo?

The servos that move the eyes and head are used in radio control cars and planes. Joysticks are used to control the action, one joystick moves the eyes and the other joystick moves the head. Each joystick controls two servos, one servo for left/right motion and the other servo for up/down motion.

The joysticks are wired to a BASIC Stamp II embedded computer from Parallax, Inc. More information is available on their web site The BASIC Stamp has a program that reads the joystick signal and sends command signals out its serial port to a serial servo controller board called the Mini SSC II from Scott Edwards Electronics.

Want to control servos with your PC or a BASIC Stamp? Purchase a Mini SSC II here.

PC Control - The Voice and Mouth Motion

The other main function of Maxwell is making the voice sounds, and making the mouth move with the voice. This is done with a PC running Windows, and a custom Visual Basic program I created.

The PC is able to move the mouth servo by sending commands out the RS232 serial port to a serial servo controller circuit board. This circuit board is the Mini SSC II from Scott Edwards Electronics, the same type of board used in the joystick control system. More info on the Mini SSC II at

Generating the voice sound is done using a piece of software called a Text to Speech Synthesizer. There are many computer speech synthesizers on the market. Microsoft has invented a standard set of commands for using a Speech Synthesizer in a Visual Basic program.

Microsoft calls this set of standard commands the Microsoft SAPI 4.0. The SAPI stands for Speech Applications Programming Interface. Not only is it a standard set of commands, but the SAPI also includes a free Speech Synthesizer engine. That synthesizer engine is used inside my program to generate the voice sound.

As the speech synthesis happens, my Visual Basic program reads back from the synthesizer what vocal sounds it is generating. Based on that, I am sending out different mouth positions for the robot's mouth to move to.

That way the mouth is the right opening for the sound that is coming out of the PC.

What about controlling the head from a Macintosh?

Check out this link for sample programs and source code for controlling the Mini SSC II servo control board from a Mac.


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