Leonardo

Kinetic Art: The Shift Register, a Circuit for Sequential Switching of LightsAuthor(s): David SmithSource: Leonardo, Vol. 5, No. 1 (Winter, 1972), pp. 59-61Published by: The MIT PressStable URL: http://www.jstor.org/stable/1572476 .

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Leonardo, Vol. 5, pp. 59-61. Pergamon Press 1972. Printed in Great Britain

KINETIC ART: THE SHIFT REGISTER, A CIRCUIT FOR SEQUENTIAL SWITCHING OF LIGHTS

David Smith*

During 1970, while a student at Sydney University in Australia and a member of the Optronic Kinetics Group there, I constructed my 'Kinetic Kaleido- scope' (cf. Fig. 1) [1]. The on-off or flashing lights in the array making up the picture are operated by an electronic circuit called a shift register. I will describe this circuit before giving details of the construction of the picture and my reflections on the application of modern technology to art.

The shift register circuit can be made easily by one who has some experience with digital switching electronics [2]. Basically, it consists of a circuit made up of any number of identical devices, called 'JK' flip-flops, connected in series as shown in the diagram in Fig. 2. A view of the circuit as it appears from the rear of the picture is shown in Fig. 3. The variable voltage output of each flip-flop controls a transistor switch that allows or disallows the current to flow through a 12 V, 2 W light bulb. The transistor conducts when the voltage output at its base is a predetermined value.

The properties of an individual flip-flop are the following: It has two voltage outputs, indicated by Q and Q in Fig. 2, each of which can have either a high or a low voltage level. The two outputs are always complementary, that is, when Q is low then Q is high and vice versa. For a change in output to occur, a trigger or initiating pulse, generated by a clock circuit, must be applied. The type of change in output is also determined by the input voltage levels on terminals J and K of each flip-flop. Each of the terminals Q and Q are connected to the input terminals J and K of the adjacent flip-flop, as indicated in Fig. 2.

If the input levels at J and K are changed and a trigger pulse is applied after each change, the follow- ing corresponding changes in output occur: When J is high and K is low, Q becomes or remains high; when J is low and K is high, Q becomes or remains low; when both J and K are high, Q remains un- changed after triggering and, finally, when both J and K are low, Q becomes the opposite of what it was before triggering.

* Electrical engineer and artist living at 16A Station Street, Pymble, N.S.W. 2073, Australia. (Received 26 August 1971.)

Fig. 1. 'Kinetic Kaleidoscope', kinetic picture with sequentially switched lights, 250 Watts, max.,

90 x 105 x 22 cm, 1970.

The output Q of any flip-flop may also be changed by applying an external voltage to it. For example, if Q is low and an external high voltage is applied to it by closing switch B, then Q will change to its high value and remain there even after the switch is opened.

When the shift-register circuit consisting of a chain of flip-flops is first turned on, the output Q of each flip-flop is low and none of the bulbs will light up. If one momentarily introduces a positive external voltage at switch B to the Q output of the first flip-flop, it will change to this value and cause the first bulb to light up. Upon this occurrence, the inputs J and K of the second flip-flop receive the new voltage and, according to the properties of the circuit described above, the first trigger pulse will cause bulb No. 1 to extinguish and bulb No. 2 to light up. The second trigger pulse causes No. 2 to extinguish and No. 3 to light up and so on.

Thus, information in the form of voltage level is passed along the chain, its presence made evident by the illumination of a bulb. The eyes see a light that appears to move continuously from bulb to bulb. When the voltage information reaches the last bulb,

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David Smith

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Fig. 2. Diagram of shift register sequent

it is directed back to the first bulb by a feed-back line and the cycle repeats itself. By introducing the change in voltage level at the first flip-flop output between trigger pulses, one can pass as many illuminating voltages as one likes. When the high voltage level is disconnected, the shift register for- gets the information it has been obeying and one can start another sequence.

The repetitive character of a sequence can be changed by automatically introducing voltage levels in an apparently random manner at the J-K inputs of the first flip-flop. This is achieved by inserting a chain code generator circuit in the feed-back loop at switch A (cf. Ref. 2, p. 143). This makes it difficult for a viewer of the picture to anticipate the behaviour of the apparent light motion.

All of the modes of operation described above can be accomplished easily by the inclusion of manually operated switches in the circuitry. For example, the switch A (cf. Fig. 2) is inserted in the feed-back path to determine whether the circuit is to operate in an automatic pseudo-random fashion or in the normal shift-register mode. The switch B may be introduced to connect a high voltage supply to the outputs of the first flip-flop to allow a viewer to control the illumination of the bulbs. The switch C, controlling the main power supply input, allows cancellation of information in the circuit. The switch D connecting the trigger pulse generator to the circuit allows removal of the trigger pulse and, hence, the freezing or holding of any group of illuminated bulbs.

The speed of the operation of the trigger circuit may be controlled by switching in different values of timing capacitors across the clock circuit (a capacitively cross-coupled dual buffer.)

My 'Kinetic Kaleidoscope' has twelve shift registers, each independently controlling a group of eight light bulbs. The 96 bulbs are supplied with a 12 V, 20 amp direct current. The bulbs were arranged in an array as shown in Fig. 4. Clipped onto the bulbs, like lampshades, are small square boxes provided with removable colour filters made of a British plastic material called 'Cinemoid'. The arrangement of the array of bulbs and of the colour

tial switching circuit for 'Kinetic Kaleidoscope'.

combinations I chose were influenced by my exposure to the paintings of Vasarely [3].

The front of the picture is a translucent or opalescent Perspex plate of 3 mm thickness. Thus, the viewer sees essentially square illuminated areas of colour appearing on the screen (cf. Fig. 1).

A shift register can be connected to any 8 light bulb sockets by means of a 96-element plug-and- socket arrangement mounted in the centre of the circuit as shown in Fig. 3. There are two control panels, one remote and one attached to the side of the picture (cf. Fig. 3).

The main control panel incorporates the switches necessary to carry out the various possible combina- tions I have described. Each of the twelve shift registers can be controlled independently. The remote control panel has an initiating and a cancel- ling switch for each shift register. Also on the remote control panel is a switch that operates a motor to drive the translucent screen to any position within a range of 8 cm in front of the bulbs. The screen is moved forward and backward by a kind of hinged concertina frame on the four sides of the picture (cf. Figs. 3 and 4). Only one driving point is needed, since the frame is sufficiently rigid to move as a whole when pushed at one point.

The shift register using sequential flip-flop for switching in the form of printed circuits, once thoroughly tested, would be trouble-free and should serve for years. It could be made in the form of a standard unit, leaving to artists the arrangements of the light bulbs and the control of their sequences of illumination by adding a few mechanical switches at desired points in the circuit.

My experience with building 'Kinetic Kaleido- scope', involving the assembly of the shift register, has reinforced certain feelings I had about the application of complex devices provided by modern technology to art. If one wishes to design the parts of complex devices and put them together oneself, several years of learning are required to acquire adequate theoretical and practical knowledge. Furthermore, one must keep abreast of new develop- ments. To play the role of artist in addition to that of engineer, demands of the individual an almost

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Notes: Kinetic Art

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Fig. 3. View of shift register sequential switching circuit for 'Kinetic Kaleidoscope'.

impossible amount of time. I was able to carry out the work of an electronic engineer and of an artist because I worked with a group of artists who had a taste for technology. Even then, I found myself so involved in the technical aspects of my picture that I sometimes became impatient to get on with its aesthetic aspects. Malina has written that he had a similar experience during the first several years of developing and applying his simpler Lumidyne system for making kinetic paintings with continuous motion of light forms [4].

Some applications of modern technology can be very expensive when compared to traditional technology used by artists, such as oil painting and stone or metal sculpting. In addition to the fixed cost of tools and components, one can consume a lot of money experimenting with devices to make them perform as desired.

Although many decry narrow specialization, I do not believe that we can expect that many who specialize in art will also become specialists in one or more fields of engineering. At best, one can hope that artists who wish to apply, for example, electrical

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Fig. 4. Front view of light bulb installation in 'Kinetic Kaleidoscope' with the translucent Perspex screen

removed.

or electronic principles and devices will obtain at least a sufficient knowledge of them to apply them imaginatively in their works and to not harm them- selves or innocent viewers.

Fortunately, for those wanting to use electronic devices and circuits, technology is making available components or units designed for different purposes that can be put into operation by making a few simple connections.

For artists with only a limited knowledge of any form of technology, there is the alternative of trying to make art by means of instruments produced for sale, such as the tape recorder, camera, television, video tape, the Moog synthesizer and, of course, the computer. These may require the effort of learning to operate or communicate with the instruments but, at least, the task is simpler and demands much less time than building special devices.

I would be glad to supply to anyone interested additional information on the technical details of the shift register circuit.

REFERENCES

1. D. Brook, Sydney: Art in the Universities, Studio Int. 182, 9 (No. 935, 1971). 2. Electronic Counting Circuits, Techniques, Devices, Ed., E. J. Kench (London: Mullard,

Ltd., 1967). 3. Vasarely (Neuchatel, Switzerland: Editions du Griffin, 1969). 4. F. J. Malina, Kinetic Painting: The Lumidyne System, Leonardo 1, 25 (1968).

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