Build Your Own Chaotron

Copyright 2008 James W. Wiggins.  All rights reserved.
Header image:  A frame from
the sculpture numerical
simulation movie.  August,
Building a Chaotron requires several steps.

1)  Decide on a mechanical device with several degrees of freedom, or in other words,
three or more partially free pieces.  In my three-arm Chaotron, the pieces are the rotating
arms that are constrained by attachment at their pivots but free to rotate independently.
The pieces should be somewhat different in size, weight and other characteristics so that
they naturally move somewhat differently.

2)  Decide on how the device will be driven.  At least one of the parts will need active
propulsion such as a motor.  In my three arm Chaotron, the largest arm is driven by a
small electric motor.

3)  The pieces that do not have a motor attached will need some means of being driven
by the motion of the other parts.  This can be done by placing magnets, springs, or other
passive devices that can transfer force from one part to another.

4)  Provide an electrical circuit to control the force applied to the moving parts.  Each
active driver should apply just enough force to overcome friction and air resistance, but
not apply enough force to control the motion in a deterministic way.

In my three-arm Chaotron, the driver consists of an angular position sensor to detect the
position of the motor shaft and the attached large arm and a driver circuit to activate the
motor in clockwise and counter-clockwise directions.  A microcontroller receives the
position data and switches on the motor whenever the arm is moving with a force just
strong enough to overcome bearing friction and air resistance.  If the arm slows down
enough to indicate that it may stop, the controller switches off the motor and waits until the
arm begins to move faster than the cutoff threshold again.  A fixed amount of work is
allowed on the arm for each time it reverses direction.  This allowance determines that
the arm can rotate a full rotation sometimes but does not rotate fully for an extended

Information on the circuit used to drive the motor is shown

The microcontroller code is shown

Copyright 2008 James W. Wiggins.  All rights reserved.
Copyright 2008 James W. Wiggins.  All rights reserved.
Copyright 2015 James W Wiggins