Electronic Sculpture Archive
Bruce Cannon

This site is an archive of my older interactive,  electronic and computer-controlled sculpture.  You can always find out about my latest projects via my gateway, brucecannon.com.


technical details

For an overview of this sculpture, see the TreeTime main page.

This robotic sculpture is constructed from parts of a tree reassembled and articulated using motors and cables.  There are six main joints, each moved by a large AC gearmotor at the sculpture's base.  This motor, through a crank and pulley system, alternately pushes and pulls four cables which move the joint out at the branch.  It is a unidirectional system providing an oscillating motion.  The motors are driven with 50ms pulses, so that the movement is imperceivable.

In addition, there are sixteen small DC motors which rotate tiny branchlets.  At each joint is an LED which blinks whenever the corresponding motor is pulsed.

The AC motors are driven through Crydom solid state relays, and the DC motors are driven using Seimens et al's ULN2803 transistor arrays.

Everything is controlled by a PIC16C74A microcontroller, programmed in C.  This micro has 33 i/o lines.  Eight of them are analog, and I read and compare eight CdS cells on the tree for movement detection.  Eight drive an LCD module which is used for status and feedback.  Four read front panel switches which allow deselection of features.  For example, the LEDs can be disabled.

Since there are 24 motors and 24 leds, I run a 4 wire bus to three 1-of-16 demultiplexers (74HC154).  This port extension scheme  is simple to wire, but permits only one output to be driven at a time.  For this piece, that's fine.

There is provision for the addition of an ISD 25XX sound system.  Eventually I'll add a continuous mix of ambient sound fragments.




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