US3363106A - Photo-conductor potential divider - Google Patents

Description

Jan. 9, 1968' D. M. PARK 3,353,106

PHOTO-'CQNDUCTQR POTENTIAL DIVIDER Filed June 26, 1964 34 AUDIO VO L UI\/IE AUD'O TERMINAL RESISTANCE AMPLIFIER LIGHT POSITION 30 FIG. 2

' /8I AUDIO SIGNAL SOURCE 8O FIG/I FIG. 7

MIRROR IOBVOLTAOE FIG. 9

sOuRcE B T VOLTAGE 2 2 SOURCE 94 T2 71 2 30 INVENTOR. FIG 5 Donald M. Park BY 3O fi/fffi 7 FIG T ATTORNEY United States Patent 3,363,106 PHOTO-CONDUCTOR POTENTIAL DIVIDER Donald M. Park, Raleigh, N.C., assignor to The Seeburg Corporation, Chicago, 111., a corporation of Delaware Filed June 26, 1964, Ser. No. 378,382 3 Claims. (Cl. 250209) ABSTRACT (3F THE DISCLOSURE An electric organ swell control employs a potential divider that is formed from two photo-conductor tubes which are placed in series and physically fixed in a housing adjacent the foot pedal. The audio signal voltage is applied across the divider and through a center tap, the audio signal or tone is fed to an audio amplifier. A light source mounts on the foot pedal which controls the tone and as the pedal moves the light from the source is directed toward the housing and illuminates the tubes independently and in sequence so as to swell the tone.

This invention is concerned with an electrical device which acts as a potential divider and which employs a plurality of photo-conductive elements in series, the illumination of which determines the manner in which the potential is divided. More specifically, the invention is concerned with a potential divider useful as a swell or volume control in electric organs and which can be made as a position sensitive device.

Heretofore, the pedal operated devices which have been used to increased and decrease volume in electric organ instruments have principally been mechanical with attendant undesirable noises that feed into the audio circuits. Mechanical volume controls having moving contacts also frequently get out of adjustment. A potential divider electronic in nature and utilizing a single photo conductor has been employed in the electric organ art however the single photo conductor type is exceedingly slow in turn-off response time. In fact, photo-conductors are inherently slow in turn-ofi response time and are not generally considered for fast response or relatively fast response applications. Still another approach to position sensitive potential dividers for organ pedal operation is illustrated in my prior Patent 3,042,888.

An object of the present invention is therefore to provide an electrical potential dividing device whose output voltage can be controlled by some position changing device such as an organ foot pedal.

Another object is to provide such a potential dividing device which when combined in operation with audio circuitry is inherently noiseless.

Another object is to provide such a potential dividing device which utilizes a plurality of photo-conductor elements in series and thereby gains a relatively fast response.

Another object is to provide such a potential divider which is capable of producing either gradually changing or relatively rapid changing audio control voltages as desired.

These and other objects of the invention will become apparent from the description and in the drawings, in which:

FIGURE 1 is a schematic diagram of a potential dividing circuit embodying the invention.

FIGURE 2 is an audio volume versus light position curve.

3,363,196 Patented Jan. 9, 1968 IGURE 3 illustrates the invention applied to a pedal control device.

FIGURE 4 is a schematic illustration of a second embodiment.

FIGURE 5 is a schematic illustration of a third embodiment.

FIGURE 6 is a front view of one of the elements of FIGURE 5.

FIGURE 7 is a schematic illustration of a fourth embodiment utilizing a modification of one of the elements of FIGURE 5.

FIGURE 8 is a schematic illustration of a fifth embodiment.

FIGURE 9 is a schematic illustration of a sixth emment.

The invention comprises in a broad sense an electrical potential divider formed from a group of photo-conductor tubes placed in electrical series, with a minimum of two tubes, and with means to illuminate each tube independently of illuminating the other tubes to the same degree of illumination. When a potential is placed across the divider, the potential at a fixed center tap will vary as one or the other of the tubes are illuminated.

A number of forms of the invention will be described from which it can be seen that the desired independent control of illumination on each tube can be gained in various ways one of which is by relative change of position between a light source and the tubes. Such control of individual tube illumination can also be gained by stationing a fixed light source opposite each photo conductor tube and then varying the intensity of the fixed light sources in difiering amounts such as by shading the light sources differently or by electrically varying the intensity of the light sources differently.

In FIGURE 1, a schematic diagram illustrates the invention in one of its basic forms and in which 20 represents a light source suitably energizing through conductors 21, 22. Light source 24) is arranged such that it can be physically moved along an arcuate path such as that indicated at 23 and as it moves assume any of the indicated positions 17. Fixedly positioned opposite light source 26 and at separate stations there is located a pair of photo conductor tubes 30, 31 which may for example be type A35 made by General Electric Company of Schenectady, NY. Tubes 3 9, 31 in the example illustrated are connected in electrical series between a typical audio signal source 32, which may be AC or DC, and ground at 33. An audio amplifier 34 is connected to a junction point 35 between the photo conductor tubes 30, 31, it being desired to control the volume of audio amplifier 34 according to the physical position of light source 20. Junction point 35 can be considered as being a fixed center tap on a potential divider comprising the series connected tubes 39, 31 and across which appears such potential as is produced by signal source 32.

As light source 21 approaches either of the tubes 30 or 31, in FIGURE 1 it can be seen that the resistance of the tube so illuminated will decrease radically assuming of course that light source 29 is sufiiciently strong in illumination and sufficiently close to the individual tube to achieve such result. As light source 20 moves for example from say position 1 to position 7, the effective resistance offered audio signal source 32 between terminals T and T may be systematically reduced, with an appropriately designed circuit, in substantially even graduations until minimum resistance between T and T '3 and maximum volume, corresponding to maximum potential at T are achieved.

The described result is generally illustrated in the curve 44) of FIGURE 2. While illustrated as a linear curve, it will be'appreciated that in the actual apparatus employing the invention as later discussed this relation may not in fact be linear. In any event, it should be noted that as light source 20 moves toward tube 30, tube resistance will decrease rapidly due to a very rapid turn-on time. At the same time, tube 31 resistance will be increasing in' view of a lessening of illumination intensity on it. That is, the tubes are illuminated differentially or in differing amounts. However, the decay or turn-ofi time of tube 31 has substantially no influence on the volume changing time since the turn-on time of tube 3-3 is much faster and asserts the greater influence. Shading of the respective lamps as indicated at 41 and 42 may assist in a sharper volume change when light source 2i) is placed in motion.

FIGURE 3 illustrates an application of the invention to anvelectric organ having a foot pedal 56 pivotally mounted on an axis 51 and supporting at its free end a housing 52 bearing light source 28. Oppositely disposed to light source 20 is a fixed housing 53 mounting the photo conductor tubes 30, 31 and being arranged for connection to terminals T T T indicated in FIGURE 1. According to the previous explanation it can be seen that as pedal 50 pivots downwardly, the volume of audio amplifier 34 can be made to increase or swell rapidly.

Of particular interest is the fact that theadvantages of the invention can be achieved in a variety of forms some of which are illustrated in the remaining figures. In FIGURE 4 for example, there is a schematic illustration showing that the same etfect may be achieved by fixing the light source 20 and arranging the housing represented by 53' (compared to housing 53 seen in FIGURE 3) such that it can be moved along an arcuate path as represented at 60 in FIGURE 4. FIGURES 1, 3 and 4 thus basically illustrate the concept of relative motion between the light source 26 and the photo conductor tubes 30, 31.

FIGURES 5, 6 and 7 schematically illustrate two other embodiments utilizing a fixed light source. Both of these embodiments follow the concept of having a moving member other than the light source or the photo conductor tubes and which acts to vary illumination by variable shielding. In FIGURE 5, source 20 is fixed. Element 79 represents a thin, curved sheet mounted on a lever 71 and a pivot 72 for pivotal motion. Sections A and C are relatively transparent and section B is relatively opaque as also indicated in the front view of element 70 shown in FIGURE 6. Thus, as member 70' is pivoted, its position can be used to control light transmission and thereby control volume in the same general manner as previously explained. 1

By making element 76 of an entirely opaque material,

another modification of the invention is shown in FIG- URE 7 in which 80 represents such a curved sheet element similar to element 70 but in this case having a suitably shaped aperture 81 which can be used to control light fiow as previously explained. V

In FIGURE 8 each of the photo conductor tubes 30,

31 is fixed and each is illuminated by fixed separate re- Slider 92 may for example be controlled by an organ foot pedal such as shown in FIGURE 3 which allows a completely remote operation since only the resistor 94 4 and slider 92 would be required at the site of the foot pedal.

A final variation of the invention is shown in FIGURE 9 in which appears a series configuration including neon lamps 90, 91 and additional photo conductor tubes 109, 101 between which at 102 is connected a voltage source 103. The light source 20 is fixed but is reflected on photo conductor tubes 160, 101 by means of a movable mirror 165. The circuit of FIGURE 9 actually employs the invention twice in that potential dividers based on the inventions teaching exists both between lamps and 91 as well as between terminals T and T One potential divider controls the other potential divider since illumination of lamps 96 and 91 vary with the position of mirrcr 195. Consequently the voltage in terminal T varys with the position of mirror 165. The circuit of FIGURE 9 like that of FIGURE 8 is thus readily applicable to remote type operation since mirror 105 could for example be operated by an organ foot pedal.

Nhile various arrangements of photo conductor devices could be employed in plural numbers and in series and parallel networks, it is deemed essential to have at least a pair of such devices across which the potential can be applied and between which there can be a controllable potential terminal such as terminal T Furthermore whatever light source means is employed to illuminate the photo conductor tubes whether a single or plural source or whether fixed or movable the light source must be proximate the tubes that are being illuminated through the mirror concept, for example, of FIGURE 9 gives some latitude in this regard. By comparing all of the embodiments illustrated, it will also be noted that each is characterized by having a control means which effectively controls the light and because of this, the potential at T Thus, control means can be the light source itself as in FIGURES 1 and 3, the photo conductor device housing as in FIGURE 4, or a movable film, wiper contact or mirror as in FIGURES 5, 8 and 9.

One possible and in some cases ideal resistance variation between terminals in a FIGURE 1 type configuration is illustrated in FIGURE 2 by curves 125, 126 and 127. Curve represents the resistance between terminals T and T which, with proper design, can be kept as a relatively constant value. Curve 126 represents the resistance between terminals T and T whereas curve 127 represents the resistance between terminals T and T Thus, with an appropriately selected design, the resistance between terminals T and T can be kept relatively constant whereas the resistance between terminals T and T and between terminals T and T can be made to vary oppositely as the position of the particular position control device is changed.

Having described the invention, I claim: 1. In an electric organ, swell control, in combination: (a) a potential divider comprising a pair of photoconductor devices connected in electrical series and including a pair of end terminals and a center tap terminal; (b) an audio signal voltage source connected to said end terminals across said divider;

(c) an audio amplifier connected to and having its volume controlled by the voltage at said center tap;

(d) a foot control for controlling said amplifier volume including a pivotly mounted foot pedal;

(e) a light source mounted on and movable with said pedal in an arcuate path;

(f) housing means supporting said photo-conductor devices one above the other and proximate said path whereby the light therefrom strikes one and then the other of said devices as said pedal pivots downwardly; and

(g) shading means effective to shade said devices differently such that as said pedal pivots downwardly the light from said source strikes said devices in sequence and in changing quantity to produce a predetermined changing voltage at said center tap and thereby control the swell of said volume according to said voltage. I

2. In an electric organ as claimed in claim 1 wherein said devices are positioned and said shading means is arranged such that as said pedal pivots downwardly the turn-on response time of the lower of said devices predominates and provides a substantially quick response in said swell control.

3. In an electric organ as claimed in claim 1 wherein said devices, light source and shading means are arranged such that the audio-volume light source position relation is substantially linear.

References Cited UNITED STATES PATENTS Lord 250209 Corwin 250229 X Bostrom et a1. 250-239 Tomasulo et a1 250-211 Gomez 250206 X Thomson 250-209 X Thorpe 250-209 Plaisance 250-229 RALPH G. NILSON, Primary Examiner.

M. A. LEAVITT, Assistant Examiner.

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