CA2314843A1

CA2314843A1 - Light-sensitive voltage dividers and use in x-y input devices

Info

Publication number: CA2314843A1
Application number: CA 2314843
Authority: CA
Inventors: John L. Lautzenhiser
Original assignee: Magitek com LLC
Current assignee: Magitek com LLC
Priority date: 1999-08-03
Filing date: 2000-08-02
Publication date: 2001-02-03

Abstract

A light-sensitive voltage divider includes a light-sensitive device.
Preferably, two series connected light-sensitive devices and two resistors are used to provide a light-sensitive voltage divider that not only is lumen balanced, but that also provides a null voltage in the absence of light. A
single-axis input device includes one of the light-sensitive voltage dividers, a lamp as a source of light, and means for selectively controlling transmission of light from the lamp to the light-sensitive voltage divider in response to a mechanical input. The means for controlling transmission of light includes light-control caps, a mirrored surface, and a light-restricting fluid. Joystick X-Y input devices and tilt-actuated X-Y input devices each include two of the light-sensitive voltage dividers. Selective control of proportionality, selective control of the rate of start-up, and selective control of the rate of shut-down are achieved by selectively controlling the rate of change of lumens of light produced from the lamps. Selective control of the lumens of light is achieved by a light-intensity control which is, optionally, a part of each one of the X-Y input devices.

Description

TITLE OF THE INVENTION
LIGHT-SENSITIVE VOLTAGE DIVIDERS AND USE IN X-Y INPUT DEVICES
BACKGROUND OF THE INVENTION
Field of the Invention The present invention relates generally to light-sensitive devices. More particularly, the present invention pertains to light-sensitive circuits, and use of light-sensitive circuits in both tilt-actuated X-Y input devices and joystick X-Y
input devices.
Description of the Related Art The speed of electric, hydraulic, and pneumatic actuators, both rotary and reciprocating, often is controlled by input apparatus that receives a mechanical input and then produces an electrical output proportional to the mechanical input.
For use in electrically propelling a wheelchair, commonly an X-Y input device receives mechanical inputs with respect to X and Y axes, and produces electrical outputs proportional to mechanical inputs with respect to the axes.
Various types of devices have been used in X-Y input devices, but the two most common utilize rotary-shaft potentiometers and non-contacting inductive devices. Rotary-shaft potentiometers have the disadvantage of a limited service life, as do any variable resistance devices that depend upon a mechanical wiper.
In contrast, X-Y input devices that use induction-type devices inherently have long life, and they have high reliability. One of their weaknesses is that centering voltages are not precise. Typically they vary by plus or minus ten percent.
However, their greatest weakness is that they are sensitive to both radio-frequency interference (RFI) and electro-magnetic interference (EMI).
Therefore, currents can be induced into them from external fields which can result in unwanted, and even dangerous, maneuvers of a power wheelchair, or any other machine, using inductive input devices.
Hall-effect X-Y input devices are available from CH Products, Vista, CA.
The manufacturer states that, in contrast to induction X-Y input devices that are sensitive to both RFI and EMI, Hall-effect X-Y input devices are practically

2 impervious to RFI and EMI distortions. Certainly, they are less sensitive to RFI
and EMI than induction-type X-Y input devices, but not necessarily totally immune from these fields. In addition, the choice of input voltages and output signals is very limited with Hall-effect input devices.
Capacitance and light-sensitive X-Y input devices have been proposed.
Rosenthal, in U.S. Patent 3,934,181, issued 20 January 1976, teaches the use of four, active, light-responsive devices in which a joystick maneuvers a mask between a light source and four light-responsive devices.
X-Y input devices of the joystick type are commonly used to control not only the speed, but also the steering of electrically propelled wheelchairs.
First and second electric motors are drivingly connected to respective ones of left and right wheels, so that steering and pivotal turns are controlled by selectively controlling speeds and directions of rotation of the two electric motors.
It is possible to achieve some degree of steering control by starting, stopping, and reversing the direction of rotation of the motors. One such device is taught by Glaser et al., in U.S. Patent 4,523,769, issued 18 June 1985.
And, a head-actuated on-off control is taught by Selwyn in U.S. Patent

3,374,845, issued 26 March 1968.
However, achieving adequate controllability requires conditioning the output signals of the X-Y input device. This signal conditioning is taught by Lautzenhiser, in U.S. Patent 5,012,165, issued 30 April 1991; in U.S. Patent 5,635,807, issued 3 June 1997; and also in a Continuation-in-Part Application, S/N 08/864,466, filed 28 May 1997, now abandoned.
As taught by Lautzenhiser, it is important to provide a predictable null voltage, or no-speed voltage, and also to provide both soft starts and soft stops for power wheelchairs. Even if an emergency stop is demanded, it must not be made with an abruptness that will catapult the occupant out of the wheelchair, nor should a start be with such abruptness as to be disconcerting.
An ideal X-Y input device should provide maximum resolution, have very little stiction, have minimal hysteresis, have a definite null, have very little tendency to overshoot or oscillate, be able to operate with minimal electronic damping, be insensitive to radio frequencies and magnetic fields, avoid producing electrical fields that could interfere with sensitive electronic equipment, operate over a wide range of ambient temperatures, produce X-Y
signals without resorting to mechanical-electrical components such as potentiometers, and have exceptional reliability and dependability.
Further, to enhance controllability, an ideal X-Y input device should provide selectably adjustable sensitivity. And, for use as a tilt-actuated head control, or body-component-actuated control, an ideal X-Y input device will be so light that a person will forget that it is on one's head, and so compact that it can be hidden in one's hair.
BRIEF SUMMARY OF THE INVENTION
A light-sensitive voltage divider includes a pair of light-sensitive devices that are connected in series, and a pair of resistors, each paralleling one of the light-sensitive devices. The light-sensitive devices may be photoresistors, phototransistors, photodiodes, or any other suitable light-sensitive device. A
light source is provided and a means is made for selectively transmitting light to the light-sensitive devices.
At a mechanical null, a null voltage is provided which may be half of the source voltage, or any desired percentage of the source voltage.
Preferably, the null voltage occurs, not only when both light-sensitive devices are exposed to the same quantity of light, but also when both light-sensitive devices are isolated from the source of light.
Since a null voltage is produced by transmitting equal quantities of light to the two light-sensitive devices, and also by isolating both of them from light, two distinct designs are possible.
An increasing quantity of light may be selectively transmitted to one light-sensitive device while simultaneously decreasing light transmitted to another light-sensitive device as a joystick is moved from a null position wherein an equal quantity of light is delivered to both light-sensitive devices, thereby providing a "light null." Or, both light-sensitive devices may be isolated from the light when at the null condition, thereby providing a "dark null."

4 A dark null provides a null whose position is exceptionally precise. It is as precise as a pair of voltage-dividing resistors are matched. Another advantage of a dark null is that, anywhere in an electrical system that uses an X-Y input device with the light-sensitive devices, or by any suitable means remote from the input device, an electrical null can be achieved by reducing the lamp voltage to zero, thereby forcing the output to its dark null.
Two of the light-sensitive voltage dividers are used in an X-Y input device, one for each axis. When two of the light-sensitive voltage dividers are used in a tilt-actuated X-Y input device, transmission of light from the light source to the four light-sensitive devices is controlled by an opaque, or otherwise light-restricting, fluid. And when two light-sensitive voltage dividers are used in a joystick X-Y input device, transmission of light to the four light-sensitive devices is controlled by movement of the joystick.
Intensity of the light source can be selectively varied, thereby providing selectively adjustable sensitivity, without changing the null point of the input apparatus.
Optionally, as will be discussed, the parallel-connected resistors can be omitted. Or, a light-sensitive voltage divider can be constructed using a single light-sensitive device.
Finally, by simply controlling the rate of change of the lumens of the light source, the X-Y input devices provide selectably adjustable soft starts and soft stops.
In a first aspect of the present invention, an input device comprises: a null-balanced light sensor; a source of light; and means for controlling transmission of the light from the source to the null-balanced light sensor proportional to a mechanical input.
In a second aspect of the present invention, a tilt-actuated input device comprises: a housing having an enclosed chamber; a first light-sensitive device being disposed with respect to a first axis, being operatively attached to the housing, and being in light-receiving communication with the enclosed chamber; a source of light being operatively attached to the housing, and being in light-transmitting communication with the first light-sensitive device through the enclosed chamber; and means for controlling the transmission of light from the source to the first light-sensitive device proportional to tilting of the housing with respect to a second axis.
In a third aspect of the present invention a joystick X-Y input device comprises: a housing having an enclosed chamber; a first light-sensitive voltage

5 divider being disposed with respect to a first axis, being operatively attached to the housing, and being in light-receiving communication with the enclosed chamber; a second light-sensitive voltage divider being disposed with respect to a second axis, being operatively attached to the housing, and being in light-receiving communication with the enclosed chamber; a source of light being operatively attached to the housing, and being in light-transmitting communication with the first and second light-sensitive voltage dividers through the enclosed chamber; means for controlling transmission of the light from the source to respective ones of the first and second light-sensitive voltage dividers proportional to an X-Y input; and a joystick being operatively attached to the means for controlling, and being pivotally moveable with respect to X and Y
axes.
In a fourth aspect of the present invention, a tilt-actuated X-Y input device comprises: a housing having an enclosed chamber; a first light-sensitive voltage divider being operatively attached to the housing, being oriented with respect to a first axis, and being in light-receiving communication with the enclosed chamber; a second light-sensitive voltage divider being operatively attached to the housing, being oriented with respect to a second axis; and being in light-receiving communication with the enclosed chamber; a source of light being operatively inserted into the housing, and being in light-transmitting communication with the first and second light-sensitive voltage dividers through the enclosed chamber; and means for controlling transmission of the light from the source to the light-sensitive voltage dividers proportional to tilting of the housing with respect to X and Y axes.
In a fifth aspect of the present invention, a light-sensitive voltage divider comprises: first and second input nodes; an output node; a first resistive device being connected to the first input node and the output node; a second resistive device being connected to the second input node and to the output node; and one of the resistive devices comprises a first light-sensitive device.

6 In a sixth aspect of the present invention, a method for producing an electrical output in response to a tilt-angle input comprises: providing a light in an enclosed chamber; exposing a light-sensitive device to the light through the enclosed chamber; and controlling transmission of the light to the light-sensitive device as a function of the tilt-angle input.
In a seventh aspect of the present invention, a method for producing an electrical output in response to a mechanical input comprises: providing a source of light in an enclosed chamber; exposing a light-sensitive voltage divider to said source of light through said enclosed chamber; and controlling transmission of said light from said source to said light-sensitive device as a function of said mechanical input.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
FIGURE 1 is a schematic drawing of a preferred embodiment of the light-sensitive voltage divider of the present invention;
FIGURE 2 is a schematic drawing of a light-sensitive voltage divider that is simpler than that of FIGURE 1, but that does not include all of the desirable features of the FIGURE 1 embodiment;
FIGURE 3 is a schematic drawing of an X-Y input device in which two light-sensitive voltage dividers each use a pair of photoresistors as light sensitive devices, and a "+" symbol indicates that the light-sensitive voltage dividers respond separately to actuation with respect to X and Y axes;
FIGURE 4 is a schematic drawing of an X-Y input device that is the same as that of FIGURE 3, except that an "x" symbol indicates that both of the light-sensitive voltage dividers of FIGURE 4 produce outputs in response to actuation with respect to both X and Y axes;
FIGURE 5 is a schematic drawing of an X-Y input device that is the same as that of FIGURE 3, except that phototransistors are used instead of photoresistors;
FIGURE 6 is a schematic drawing of an X-Y input device that is the same as that of FIGURE 4, except that phototransistors are used instead of photoresistors;

7 FIGURE 7 is a schematic drawing of an X-Y input device that is the same as that of FIGURES 4 and 6, except that photodiodes are used for the light-sensitive devices;
FIGURE 8 is a schematic drawing of an X-Y input device that is similar to those of FIGURES 3-7, one difference being a trim potentiometer that is inserted in series with each light-sensitive device;
FIGURE 9 is an enlarged and cross-sectioned elevation of a preferred embodiment of a joystick X-Y input device that includes two of the light-sensitive voltage dividers of FIGURES 1-8, showing the joystick X-Y input device mounted in a hole in a plate, one-half of a boot thereof, and a mounting ring;
FIGURE 10 is an enlarged and cross-sectioned elevation of the joystick X-Y input device of FIGURE 9, taken substantially the same as FIGURE 9, but with the joystick tilted to an angle, and with the boot removed;
FIGURE 11 is an enlarged and cross-sectioned elevation of a preferred embodiment of a tilt-actuated X-Y input device, taken substantially as shown by Section Line 11-11 of FIGURE 13, showing mercury partially covering the light-sensitive devices, and showing the mercury being dimpled by the lamp and the light-sensitive devices;
FIGURE 12 is an enlarged and cross-sectioned elevation of the tilt-actuated X-Y input device of FIGURE 11, showing the mercury obscuring light from one of the light-sensitive devices, while increasing transmission of light to the other light-sensitive device; and FIGURE 13 is a top plan view that shows the light-sensitive devices of FIGURES 11 and 12, and that also shows dimpling of mercury by the light-sensitive devices.
FIGURE 14 is an enlarged cross-section of another embodiment of a tilt-actuated X-Y input device of the present invention, that includes two of the light-sensitive voltage dividers of FIGURES 1-8, and that may be used with a light-intensity control as shown in FIGURES 24 or 25, taken substantially as shown by Section Line 14-14 of FIGURE 15, and showing only one of the four resistors;

8 FIGURE 15 is a cross-section of the tilt-actuated X-Y input device of FIGURE 14, taken substantially as shown by Section Line 15-15 of FIGURE 14, but with a light-restricting fluid added;
FIGURE 16 is a cross-section of the tilt-actuated X-Y input device of FIGURES 14 and 15, taken substantially the same as FIGURE 15, but with a cap added, and with the tilt-actuated X-Y input device tilted to an actuating angle, thereby proportioning transmission of light from the electric lamp to the light-sensitive devices unequally;
FIGURE 17 is a cross-section of another embodiment of a joystick X-Y
input device of the present invention, taken substantially as shown by Section Line 17-17 of FIGURE 18, that includes two of the light-sensitive devices of FIGURES 1-8, and that may be used with a light-intensity control as shown in FIGURES 23 or 24;
FIGURE 17A is a partial cross-section of the joystick X-Y input device of FIGURE 17, taken substantially the same as FIGURE 17, showing the light-sensitive devices disposed above a bottom surface of the light-control cap to provide a dead band, and showing the light-control cap tilted at an angle by the joystick of FIGURE 17;
FIGURE 18 is a reduced-scale cross-section of the body of the X-Y input device of FIGURE 17, taken substantially as shown by View Line 18-18 of FIGURE 17, showing the light-sensitive devices oriented on the X and Y axes;
FIGURE 19 is a symbolic view, taken substantially the same as FIGURE
18, showing the light-sensitive devices oriented at 90 degrees to each other and 45 degrees from the X and Y axes, thereby providing equal speed and turn signals when a joystick is moved in the X and Y directions;
FIGURE 20 is another symbolic view, taken substantially the same as FIGURE 18, showing the light-sensitive devices oriented closer to the X axis than to the Y axis, thereby providing a speed signal that is larger than a turn signal when a joystick is moved in the X direction;
FIGURE 21 is still another symbolic view, taken substantially the same as FIGURE 18, showing the light-sensitive devices oriented closer to the Y
axis than to the X axis, thereby providing a turn signal that is larger than a speed signal when a joystick is moved in the Y direction;

9 FIGURE 22 is a cross-section of a third embodiment of a joystick X-Y
input device of the present invention, taken substantially as shown by Section Line 22-22 of FIGURE 23, that includes two of the light-sensitive voltage dividers of FIGURES 1-8, and that may be used with a light-intensity control as shown in FIGURES 24 or 25;
FIGURE 23 is a bottom view of the joystick X-Y input device of FIGURE 22, taken substantially as shown by View Line 23-23 of FIGURE 22, and showing the light source in the center of four, radially disposed, light-sensitive devices;
FIGURE 24 is a schematic drawing of a light-intensity control for the light-sensitive voltage dividers of FIGURES 1-8, and for the X-Y input devices of FIGURES 3-23; and FIGURE 25 is a schematic drawing of a preferred embodiment of a light-intensity control for the light-sensitive voltage dividers of FIGURES 1-8, and for the X-Y input devices of FIGURES 3-23.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGURE 1, a lumen-balanced light-sensitive voltage divider, or null-balanced light sensor, 10 includes first and second light-sensitive devices, photoresistors, photodiodes, or phototransistors, 12A and 12B. The light-sensitive devices 12A and 12B are connected in series, and first and second series parallel-connected resistors 14A and 14B preferably are connected in parallel with respective ones of the light-sensitive devices 12A
and 12B by connecting nodes 16A and 16B, and by connecting nodes 16C and 16D.
The nodes 16A, 16B, 16C, and 16D have been included in FIGURE 1 to facilitate discussion of the operation of FIGURE 1 both with and without the resistors 14A and 14B. While the voltage divider 10 may be constructed without the resistors 14A and 14B, better and more versatile operation is achieved by including the resistors 14A and 14B, as will be discussed subsequently. However, in the discussion that follows, the nodes 16A, 16B, 16C, and 16D are connected as described above.

The light-sensitive devices 12A and 12B used to practice the present invention may be selected from photoresistors, phototransistors, photodiodes, and any other suitable light-sensitive device. Therefore, they will be referred to generically as light-sensitive devices 12A, and 12B, except when referring to 5 specifics of one type of light-resistive device.
Assuming that the light-sensitive devices, 12A and 12B are photoresistors, in the absence of light, resistances of the light-sensitive devices 12A and 12B increase to five or six megohms, and in the presence of strong light, their resistances reduce to about 600 ohms. Resistances in the vicinity of

10 a few thousand ohms can be achieved by a five volt subminiature bulb operating at less than half of its rated voltage, or by a conventional LED
lamp operating at less than half of its rated current.
The resistors 14A and 14B have equal resistances, and the light-sensitive devices 12A and 12B have high resistances, or are essentially open, in the absence of light. Therefore, when connected to a positive potential and to ground, as shown, an output node, or output-voltage node, 18 will be provided with a voltage that is one-half of the voltage of the source, as determined by the resistors 14A and 14B.
Further, when the light-sensitive devices 12A and 12B are subjected to the same light intensities, their resistances will decrease to substantially equal resistances, so that the voltage in the node 18 will still be half of the voltage of the source.
Continuing to refer to FIGURE 1, an electric lamp, or source of light, 20 is shown proximal to the light-sensitive devices 12A and 12B, although the electric lamp 20 is not a part of the light-sensitive voltage divider 10. The light intensity of the lamp 20 can be varied to any reasonable value by any suitable means, or even shut off, without changing the null voltage at the node 18.
Referring now to FIGURE 2, a light-sensitive voltage divider 26 includes a light-sensitive device 12A in series with a dividing resistor, or variable resistor, 28 whose resistance is variable by positioning a wiper 30.
Preferably, the light-sensitive voltage divider 26 also includes a null-balance resistor, or second variable resistor, 32 whose resistance is variable by positioning a wiper 34.

First, assuming that the nodes 36A, 36B, 36C, and 36D are not connected, adjustment of the wiper 30 will provide a null voltage at an output node, or output-voltage node, 38 that is any desired percentage of the source voltage applied to positive and ground terminals for a given quantity of light source voltage transmitted to the light-sensitive device 12A.
If a photoresistor is used for the light sensitive device 12A, in the absence of light, its resistance will increase to about 6.0 megohms, so that a voltage at the output node 38 will be approximately zero volts. However, by connecting the nodes 36A and 36B, and by connecting the nodes 36C and 36D, a definite null voltage will be provided at the node 38 by the null-balance resistor 32, even when the photoresistor 12A is in the dark.
A change in light intensity of the lamp 20 changes the resistance of the light-sensitive device 12A, thereby changing sensitivity of the light-sensitive voltage divider 26, but also shifts the null voltage. If the nodes 36A, 36B, 36C, and 36D are disconnected, this shift in null voltage is great, because it is dependent entirely upon the variable resistance of the light-sensitive device and the fixed resistance of the resistor 28.
If the nodes 36A, 36B, 36C, and 36D are connected as described above, the shift in null voltage is much less, because a change in the parallel-connected resistance of the light-sensitive device 12A and the null-balance resistor 32 is much less than a resistance change in the light-sensitive device 12A alone.
Contrasting the designs of FIGURES 1 and 2, the light-sensitive voltage divider 10 of FIGURE 1 is preferred, because its null does not shift when the light intensity of the lamp 20 is changed. No matter what the light intensity of the lamp 20, if equal lumens are transmitted to both light-sensitive devices and 12B, they produce equal resistances. Therefore, the light-sensitive voltage divider 10 of FIGURE 1 is lumen balanced.
In the embodiment of FIGURE 1, a change of light intensity of the lamp 20 does not shift the null voltage whether the nodes 16A, 16B, 16C, and 16D
are connected or disconnected. However, connection of the nodes 16A, 16B, 16C, and 16D, and thereby inclusion of the resistors 14A and 14B, not only provides a more definite null, but also provides a definite null even when the lamp 20 is dark.
Inclusion of the resistors 14A and 14B in the light-sensitive voltage divider 10 of FIGURE 1 provides better control of sensitivity. A subsequent decrease in the resistance of one device 12A or 12B, and an increase in the resistance of the other device 12B or 12A, as controlled by an X-Y input device, is attenuated by the smaller and parallel-connected resistances of the resistors 14A and 14B.
As will be apparent from subsequent discussion of FIGURES 3-23, a single light-sensitive voltage divider, 10 or 26 can be used to make a mechanical-to-electrical input device, or a pair of the light-sensitive voltage dividers, 10 or 26, can be used to make an X-Y input device.
The light-sensitive voltage divider 10 may be used to construct X-Y
input devices with either a light null or a dark null. In an X-Y input device with a light null, the source of light 20 is allowed to transmit light equally to the light-sensitive devices, 12A and 12B when the mechanical input is at its null position. Conversely, in an X-Y input device with a dark null, the light-sensitive devices, 12A and 12B are isolated from the source of light 20 when the mechanical input is at its null position.
Referring now to FIGURE 3, an X-Y input device, or two-axis mechanical-to-electrical input device, 44 includes light-sensitive voltage dividers, or null-balanced light sensors, 46A and 46B. The light-sensitive voltage dividers 46A and 46B each include a pair of light-sensitive devices, or photoresistors, 48 that are connected in series between a positive input node and ground.
Output nodes, or output-voltage nodes, 52A and 52B are connected intermediate the aforesaid series connections of respective ones of the photoresistors 48, as shown, so that the output nodes 52A and 52B are output nodes for respective ones of the light-sensitive voltage dividers 46A and 46B.
Four resistors 54 provide functions for their respective light-sensitive voltage dividers 46A and 46B, as discussed in conjunction with FIGURE 1.
The X-Y input device 44, as symbolically represented in FIGURE 3, may be a joystick X-Y input device in which a joystick controls light from the lamp 20 of FIGURE 1 to the various ones of the photoresistors 48 in response to movement of the joystick with respect to X and Y-axes, as taught herein.
Or the X-Y input device 44 may be a tilt-actuated X-Y input device in which tilting of a housing with respect to the X and Y-axes proportionally places a light-restricting fluid between the lamp 20 of FIGURE 1 and various ones of the photoresistors 48, as taught herein.
Proportioning means 56, shown as a plus "+" symbol in FIGURE 3, indicates that actuation of the proportioning means 56 with respect to the X-axis controls lumens of light transmitted from the lamp 20 of FIGURE 1 to the photoresistors 48 of the light-sensitive voltage divider 46A exclusively, and proportionally controls a voltage at the output node 52A. In like manner the "+" symbol indicates that actuation of the proportioning means 56 with respect to the Y-axis controls the light-sensitive voltage divider 46B, exclusively, and proportionally controls a voltage at the output node 52B.
As is well known in the industry, some power wheelchairs use joystick X-Y input devices that function in the manner described in conjunction with FIGURE 3, above.
Alternately, as taught in FIGURE 4 below, both of the light-sensitive voltage dividers 46A and 46B may be used to control not only forward and reverse directions of both left and right propulsion motors and their speeds, but also differential speeds of the propulsion motors.
Referring now to FIGURE 4, an X-Y input device, or two-axis mechanical-to-electrical input device, 62 includes the light-sensitive voltage dividers 46A and 46B and the components as named and numbered in conjunction with FIGURE 3. Proportioning means 64, illustrated by an "x"
symbol, indicates that actuation of the proportioning means 64, with respect to the X-axis, proportionally controls voltages at the output nodes 52A and 52B.
Actuation of the proportioning means with respect to the Y-axis also proportionally controls voltages at the output nodes 52A and 52B, but inversely, one to the other.
In FIGURES 4 and 6-8, the functioning of each light-sensitive device, such as the photoresistor 48, is designated as RMF, LMF, RMR, or LMR which stand for right motor forward, left motor forward, right motor reverse, and left motor reverse, respectively.
For instance, when a light sensitive device is labeled RMF, and when it is located proximal to the positive input node 50, rather than being proximal to the ground, an increase in light produces an increase in voltage at its output node 52A or 52B. In this example, a two-axis input device, such as the X-Y
input device 62 of FIGURE 4, is designed for systems in which an increase in voltage produces an increase in motor speed, and an increase in forward speed.
Referring now to FIGURE 5, an X-Y input device, or two-axis mechanical-to-electrical input device, 70 includes light-sensitive voltage dividers, or null-balanced light sensors, 72A and 72B. The light-sensitive voltage dividers 72A and 72B each include a pair of light-sensitive devices, or phototransistors, 74, a pair of current-limiting resistors 76 that are connected in series with respective ones of the phototransistors 74, and a pair of the resistors 54 that are connected as discussed in conjunction with FIGURE 3. The "+"
symbol of the proportioning means 56 indicates that operation is as has been discussed in conjunction with FIGURE 3.
Referring now to FIGURE 6, an X-Y input device, or two-axis mechanical-to-electrical input device, 82 includes the light-sensitive voltage dividers 72A and 72B of FIGURE 5, and other parts as named and numbered in conjunction with FIGURE 5, except that the "x" symbol indicates that the proportioning means 64 controls output voltages at both of the output nodes 52A and 52B in response to actuation with respect to the X-axis, as described in conjunction with FIGURE 4.
Referring now to FIGURE 7, an X-Y input device, or two-axis mechanical-to-electrical input device, 90 includes parts as named and numbered in conjunction with FIGURES 3 and 4, except that light-sensitive voltage dividers, or null-balanced light sensors 92A and 92B each include a pair of light-sensitive devices, or photodiodes, 94.
Output voltages at both of the output nodes 52A and 52B are controlled by actuation with respect to the X-axis, as indicated by the "x"
symbol of the proportioning means 64, and as described in conjunction with FIGURE 4, although the principles taught in conjunction with FIGURE 7 may be used with a proportioning means 56, or with any other type of proportioning mechan ism.
All of the photodiodes 94 of FIGURE 7 are reverse biased. That is, their cathodes are proximal to the positive supply voltage. When a pn junction 5 (not shown) of a photodiode is exposed to light, the reverse current increases with the light intensity.
Remembering that the RMF and RMR resistors 54 function as a voltage divider establishing a null voltage at the output node 52B, when light impinges on an RMF photodiode 94, current flow through the RMF photodiode 94 10 decreases a voltage drop from the positive input to the output node 52B, unequally dividing the source voltage, and pulling the voltage at the output node 52B upwardly.
In like manner, when light impinges on an RMR photodiode 94, current flow through the RMR photodiode 94 decreases a voltage drop from the 15 output node 52B to ground, unequally dividing the source voltage, and thereby pulling the voltage at the output node 52B downwardly.
Referring now to FIGURE 8, an X-Y input device, or two-axis mechanical-to-electrical input device, 100 includes light-sensitive voltage dividers, or null-balanced light sensors 102A and 102B. Each of the light-sensitive voltage dividers 102A and 102B includes a pair of the light-sensitive devices, or photoresistors, 48 of FIGURES 3 and 4, and a pair of trim potentiometers 104.
The trim potentiometers 104 may be used to selectively and individually proportion forward, reverse, and turn sensitivity of the light-sensitive voltage dividers 102A and 102B. Although labels in FIGURE 8, such as RMR and RMF pertain to the proportioning means 64, the X-Y input device 100 may be used with either the proportioning means 56 or the proportioning means 64.
A pair of resistors 106, that are connected in series between the positive input node 50 and the ground, provide a null voltage at a null-voltage node 108 for systems that utilize a null voltage that is developed from a source of electrical power, as applied to the positive input node 50, and a ground, or between any two voltage potentials.

In FIGURES 3 and 5, numbers 90, 180, 270, and 360 indicate angular positions of the light-sensitive devices 48 or 74 in degrees with respect to the proportioning means 56. In FIGURES 4, 6, and 7, numbers 45, 135, 225, and 315 indicate positions of the light-sensitive devices 48, 74, or 94 in degrees with respect to the proportioning means 64.
In FIGURE 8, the numbers 40, 140, 220, and 320 indicate that it is sometimes advantageous to position light-sensitive devices, such as the photoresistor 48, at angles that are not spaced a quadrant apart.
Preferred components for use in the embodiments of FIGURES 3-8 are:
photoresistor 48, part number NSL-7530, manufactured by Silonex, Inc., St.
Laurent, Quebec, Canada; phototransistor 74, part number OP505A, manufactured by Optek Technology, Inc., Carrollton, Texas; and photodiode 94, part number OSD1-ST, manufactured by Centronic Limited, Croydon Surry, England.
Preferred values for the resistors 54 are: 4.99K ohms for FIGURES 3-6 and 8, and 180K ohms for FIGURE 7. The preferred value for the resistors 76 in FIGURES 5 and 6 is 2K ohms. And the preferred value for the trim potentiometers 104 in FIGURE 8 is 10K ohms.
Referring now to FIGURES 9 and 10, a joystick X-Y input device, or mechanical-to-electrical input device, 110 includes a body, or housing, 112, an electric lamp, or source of light, 114, a wobble 116, a light-control cap 117, and a shaft, or joystick, 118, that is screwed into the wobble 116, as shown.
As can be see in the drawings, the wobble 116 and the light-control cap 117 are manufactured as a unified part.
The wobble 116 is disposed in a cylindrical cavity, or cylindrical bore, 120 of the body 112. The wobble 116 is centered, and made pivotal, by an O ring 122 that is disposed in an O ring groove 124 in the wobble 116 and that engages a cylindrical surface 125 of the cylindrical cavity 120. The wobble 116 cooperates with the cylindrical cavity 120 to provide an enclosed chamber, or ambient light-excluding cavity, 126. Further, the wobble 116 provides means for pivotally attaching the joystick 1 18 to the body 112 and to the light-control cap 117.

A spring 127 is disposed in the cylindrical cavity 120, is retained by a retaining ring 128 in a retaining-ring groove 130. The spring 127 is centered by, and presses against, a spring-centering cup 132.
The spring-centering cup 132 prevents the spring 127 from incurring friction from contact with the cylindrical surface 125, transmits force from the spring 127 to the wobble 116, and provides a low friction junction between the spring-centering cup 132 and the wobble 116, thereby allowing the spring-centering cup 132 to slide transversely, with respect to the wobble 116, as shown in FIGURE 10, when the joystick 118 is moved to a tilt angle, or mechanical input, 134 of FIGURE 10.
The spring 127 presses the wobble 116 downwardly, thereby pressing the light-control cap 117 down against a teflon washer 136 that is disposed over and around the lamp 114, and the teflon washer 136 presses against a bottom surface 138 of the cylindrical cavity 120, thereby providing a positive centering device for the joystick 118, and thereby providing a definite dark null for the light-sensitive devices 48 of FIGURES 3 and 4, the light-sensitive devices 74 of FIGURES 5 and 6, or the light-sensitive devices 94 of FIGURES 7 and 8.
Preferably, the wobble 116, the O ring 122, the cylindrical surface 125, the light-control cap 117, the teflon washer 136, and the spring-centering cup 132 are all coated with a grease, part number 49635, manufactured by Dynatex of Elizabethtown, Kentucky to provide minimum friction between operating parts.
Referring now to FIGURE 10, when the joystick 118 is actuated to the angle 134, light from the lamp 114 is transmitted to one of the light-sensitive devices, 74, proportional to the angle 134. A nonreflective black surface, or light absorbing surface, 140, that is glued inside the light-control cap 117, prevents reflected light from interfering from proportional control in the transmission of light from the lamp 114 to the light-sensitive devices 74.
Preferably the lamp 114 is a light-emitting diode, part number MV8742, manufactured by QT Optoelectronics of Sunnyvale, California. As shown in FIGURES 9 and 10, a flat is sanded on the LED to diffuse the light, and thereby reduce the quantity of light that is directed upwardly against the nonreflective black surface 140.

Referring now to FIGURES 11 and 12, a tilt-actuated X-Y input device, or two-axis mechanical-to-electrical input device, 150 includes a body, or housing, 152, a spherically-bottomed bore 154, four light-sensitive devices 74 that are disposed in bores 155, and that are circumferentially spaced as shown in FIGURE 13, a cover plate 156, an electric lamp, bulb, or source of light, that is disposed in a bore 160 of the cover plate 156, and mercury, a light-restricting fluid, or a light-blocking fluid, 162 that rests against the spherically-bottomed bore 154.
Referring now to FIGURE 11, when the tilt-actuated X-Y input device 150 is disposed at a zero tilt angle, or neutral position, 164, the mercury 162 is dimpled by the light-sensitive devices 74 as shown in FIGURES 11 and 13, and the mercury 162 is also dimpled by the lamp 158.
Referring now to FIGURE 12, when the tilt-actuated X-Y input device 150 is disposed at a tilt angle, or mechanical input, 166, the mercury 162 prevents transmission of light from the lamp 158 to one of the light-sensitive devices 74, and exposes another of the light-sensitive devices 74 to more light from the lamp 158.
Referring again to FIGURES 11 and 12, the spherically-bottomed bore 154 and the cover plate 156 cooperate to provide an enclosed chamber, or ambient light-excluding cavity, 168. As shown in the drawings, both the lamp 158 and the light-sensitive devices 74 are operatively attached to the housing 152; and both the lamp 158 and the light-sensitive devices 74 are in light-transmitting communication with the cavity 168. Preferably, the lamp 158 is a miniature lamp manufactured by Chicago Miniature Lamp of Hackensack, New jersey.
The enclosed chamber 168 provides means for transmitting light from the lamp 158 to the light-sensitive devices 74. And the light-restricting fluid 162 of FIGURES 11 and 12 provides means for restricting transmission of light from the lamp 158 to the light-sensitive devices 74.
Preferably, the body 152 and the cover plate 156 are manufactured from polyvinyl chloride, and the cover plate 156 is permanently sealed inside the spherically-bottomed bore 154 by any suitable cement such as a two-part clear epoxy sealer. One such suitable sealer is ITW manufactured by DEVCON

of Danvers, Massachusetts. Preferably, the body 152 has a diameter of about 15.9 mm. (0.625 inches), and the spherically-bottomed bore 154 has a diameter of 11.1 mm. (0.437 inches).
Preferably, the light-restricting fluid 162 is mercury. Although mercury will etch many materials, such as stainless steel, and thereby tend to become somewhat of a wetting-type material, when placed into contact with a suitable material, such as various plastics, mercury remains a nonwetting material.
Further, mercury is a metal that melts at -40 degrees Celsius, so that at ordinary ambient temperatures, it is in its fluid state. Therefore, mercury can be classified as a nonwetting fluid material.
Alternately, the light-restricting fluid 162 may be a graphited, petroleum-based fluid, although it is a wetting fluid-material. One suitable fluid is LOCK-EASE, manufactured by AGS of Muskegon, Michigan.
Referring now to FIGURES 14-16, a headband X-Y input device 180 includes a tilt-actuated X-Y input device, or two-axis mechanical-to-electrical input device, 182 and a headband 184.
The tilt-actuated X-Y input device 182 includes a cylindrical body, or housing, 186 that is disposed around a longitudinal axis 188. Four cylindrical bores 190 are circumferentially disposed around the cylindrical body 186 and extend radially inward toward the axis 188. A lower boss 192 that is square in shape, as seen in FIGURE 14, and an upper boss 194 that is also square, are spaced apart and disposed intermediate of the bores 190.
Referring again to FIGURE 14, each of the bores 190 includes a counterbore 196, and four smaller bores 198 are interspersed intermediate of adjacent pairs of the bores 190. The light-sensitive devices 12A, 12B, 12C, and 12D, are inserted into respective ones of the bores 190, and four resistors are inserted into the smaller bores 198, resistor 14A being shown inserted into one of the smaller bores 198.
The light-sensitive devices 12A, 12B, 12C, and 12D, along with the four resistors, (14A shown), cooperate to make two of the light-sensitive voltage dividers 10 of FIGURE 1. One of the light-sensitive voltage dividers 10 includes the light-sensitive devices 12A and 12B and is disposed with respect to one axis. The other of the light-sensitive voltage dividers 10 includes the light-sensitive devices, 12C and 12D and is disposed with respect to an other axis.
Referring now to FIGURES 14 and 15, a threaded stud 200 is threaded through a lower surface 202 of the body 186, through the lower boss 192, and 5 into an enclosed chamber, or ambient light-excluding cavity, 204. The chamber 204 is formed by the bores 190 and extends between the photoresistors 12A, 12B, 12C, and 12D and intermediate of the lower boss 192 and the upper boss 194.
Referring again to FIGURE 15, an electric lamp, or source of light, 206 10 is pressed down through a top surface 208 of the body 186, into a hole 210 in the upper boss 194, and down against the stud 200. Positioning the lamp 206 against the stud 200, which has been precisely positioned as a stop for the lamp 206, provides precision positioning of the lamp 206.
Referring again to FIGURES 14 and 15, the light-sensitive devices, 12A, 15 12B, 12C, and 12D, are press-fitted into the bores 190. The stud 200 is sealed with a suitable sealer, such as Retaining Compound RC-609 manufactured by Locktite Corp. of Rocky Hill, Connecticut.
The preferred assembly procedure includes: filling the chamber 204 slightly less than half full with a light-restricting fluid, light-blocking fluid, or 20 opaque fluid, 212, pressing the lamp 206 into the hole 210, and hermetically sealing the lamp 206 into the hole 210 with a sealer, such as a two-part clear epoxy sealer. One such suitable sealer is ITW manufactured by DEVCON of Danvers, Massachusetts.
Preferably, the light-restricting fluid 212 is a graphited, petroleum-based fluid. One suitable fluid is LOCK-EASE.
Referring now to FIGURE 16, a cap 214 is assembled over the body 186 and the pigtails, 216 and 218 shown, of the resistors 14A, 14B, 14C, and 14D, to form two light-sensitive voltage dividers 10 of FIGURE 1, and a cable 220 is connected to the two light-sensitive voltage dividers 10. The cap 214 is then permanently attached to the body 186 by a chemically-bonded annular joint 222.

Preferably, the electric lamp 206 of FIGURES 15 and 16 is part number 71753 ASI 15 in the T-3/4 series manufactured by Chicago Miniature of Chicago, Illinois.
Referring to FIGURES 15 and 16, the headband 184 is attached to the tilt-actuated X-Y input device 182 by the threaded stud 200 and a nut 224.
Since the headband 184 is easily removed and replaced, different colors and ornamental designs of headbands may be used to complement hair styling of girls and women. Further, since the actual size of the cylindrical body 186 of the tilt-actuated X-Y input device 182 is only 0.975 inches (24.75 mm.) in diameter and 0.394 inches (10.0 mm.) thick, the tilt-actuated X-Y
input device 182 is not only light in weight, but also may be concealed by creative hair styling.
In FIGURE 14, the headband 184 is oriented between the X and Y
axes, as needed for use with systems such as taught by Lautzenhiser et al. in U.S. Patent 4,906,906, issued 6 March 1990. However, in FIGURE 15 the headband 184 is shown aligned with the Y axis, as needed for use with control systems made by some manufacturers. Thus, by selectively orienting the headband 184, the headband X-Y input device 180 will work for either type of system.
Referring again to FIGURES 15 and 16, in FIGURE 15, the fluid 212 allows exposure of both the photoresistors 12A and 12B to the same intensity of light. But, when the tilt-actuated X-Y input device 182 is tilted to a tilt angle or mechanical input, 226 of FIGURE 16 from a neutral position 227 of FIGURE
15, the light-sensitive devices 12A and 12B are exposed to differences in light intensity that are a function of the tilt angle 226.
Referring now to FIGURES 17-21, and more particularly to FIGURES 17 and 17A, a joystick X-Y input device, or two-axis mechanical-to-electrical input device, 240 includes a cylindrical body, or housing, 242, a joystick 244, a light controller, or light-control cap, 246, an end plug 248, a spherical bearing 250, a spring 252, and the electric lamp 206.
The cylindrical body 242 includes a bearing bore 254, a larger cylindrical bore 256, a spring-receiving counterbore 258, and a plug-receiving counterbore 260. The larger cylindrical bore 256 provides an enclosed chamber, or ambient light-excluding cavity, 261. The light-control cap 246 is disposed in the cavity 261, and the lamp 206 and the light-sensitive devices 12A, 12B, 12C, and 12D, are exposed to the cavity 261.
The joystick 244 includes a joystick shaft, 262, a knob 264, and an actuator ball 266. The knob 264 and the actuator ball 266 may be attached to the joystick shaft 262 by any suitable means, not a part of the present invention.
The joystick shaft 262 extends through the spherical bearing 250 and is retained by a pair of spaced-apart retaining rings 268 that retainingly engage both the joystick shaft 262 and the spherical bearing 250. The spherical bearing 250 is retained in the bearing bore 254 by a pair of spaced-apart retaining rings 270 that retainingly engage both the bearing bore 254 and the spherical bearing 250.
All surfaces of the light-control cap 246 are surfaces of revolution.
Therefore, except for showing circumferential positions of the light-sensitive devices 12A, 12B, 12C, and 12D, the light-control cap 246 is fully disclosed in FIGURE 17.
However, particularly referring now to FIGURE 17A, the light-control cap 246 includes a spherical socket 272 that is disposed in a hub 273 and that slidingly receives the actuator ball 266, a conical recess 274 that extends upwardly to allow the electric lamp 206 to extend upwardly from the end plug 248, a light-control surface, or bottom surface 276, and a spring-receiving shoulder 278.
The spring 252 positions the knob 264 at an intersection, or neutral position, 277 of the X and Y axes of FIGURE 18 as the spring 252 presses the bottom surface 276 tightly against the end plug 248, thereby preventing light from being transmitted from the lamp 206 to any of the light-sensitive devices, 12A, 12B, 12C, or 12D, thereby increasing the resistance of each one to about 6.0 megohms if photoresistors are used for the light-sensitive devices, 12A, 12B, 12C, and 12D.
Series-connected 6.0 megohm resistors cannot function as an effective voltage divider. Therefore, if it were not for the series-connected resistors, such as the resistors 14A and 14B of FIGURE 1 which each have a resistance of about 5K ohms, a definite null voltage, corresponding to a null position of the knob 264, would not be provided.
Referring now to FIGURES 17 and 17A, as the knob 264 is positioned away from the intersection 277 of FIGURE 18, the actuator ball 266, which is slidingly fitted into the spherical socket 272, tilts the light-control cap 246 and its bottom surface 276. If the knob 264 is moved in one Y direction, as shown by an arrow 280 in FIGURE 17, the bottom surface 276 is raised on its right side, and light from the lamp 206 is transmitted to the light-sensitive device 12B.
Since the bottom surface 276 is planar, raising the bottom surface 276 on the right side also raises the entire bottom surface 276 except on the left side wherein it rests against the end plug 248. Therefore, moving the knob 264 in the direction of the arrow 280 to a tilt angle, or mechanical input, 281 of FIGURE 17 also raises the bottom surface 276 proximal to the light-sensitive devices 12C and 12D, shown only in FIGURE 18, but only one-half as much.
So the light-sensitive devices 12C and 12D receive equal amounts of light, but less light than the light-sensitive device 12B.
Referring now to FIGURE 17, a bottom surface 282 of the light sensitive devices 12A and 12B coincides, vertically, with the bottom surface 276 of the light-control cap 246, so light is transmitted from the lamp 206 to the light-sensitive device 12B in response to even the slightest tilting of the light-control cap 246.
In contrast, referring now to FIGURE 17A, the bottom surface 282 of the light-sensitive devices 12A and 12B is positioned above the bottom surface 276 as shown by a dimension, or dead band, 283, so that the larger cylindrical bore 256 cooperates with the light-control cap 246 to prevent light from being transmitted from the lamp 206 to the light sensitive device 12B until the bottom surface 276 is tilted above the bottom surface 282 of the light-sensitive device 12B. Thus, in the FIGURE 17A design variation, the dead band 283 is provided.
Referring now to FIGURES 18-21, the light-sensitive devices 12A, 12B, 12C, and 12D are oriented on X and Y axes as shown in FIGURE 18 for systems that use separate speed and turn signals. The light-sensitive devices 12A, 12B, 12C, and 12D are oriented at forty-five degrees from the X and Y
axes, on axes 284 and 285 as shown in FIGURE 19, for systems that use combined X and Y signals when equal speed and turn sensitivities are desired.
For systems in which combined speed and turn signals are used, orientation of the light-sensitive devices 12A, 12B, 12C, and 12D on axes 286 and 287, as shown in FIGURE 20, decreases turn sensitivity. In like manner, orientation of the light-sensitive devices 12A, 12B, 12C, and 12D on axes 288 and 289, as shown in FIGURE 21, increases turn sensitivity.
The light-sensitive devices 12A, 12B, 12C, and 12D can be positioned in like manner in the embodiments of FIGURES 3-16 and 22-23 to achieve similar results.
Referring now to FIGURES 22 and 23, a joystick X-Y input device, or two-axis mechanical-to-electrical input device, 300 includes two of the light-sensitive voltage dividers 10 that are shown in FIGURE 1 with the nodes 16A, 16B, 16C, and 16D connected, as described above.
Referring to FIGURES 22 and 23, but more particularly to FIGURE 22, the joystick X-Y input device 300 includes a body, or housing, 302 having a counterbore 304 with a threaded portion 306 proximal to a top surface 308.
Preferably, the body 302 is made of a black plastic to absorb light from an electric lamp, or source of light, 309, rather than reflecting light. A
joystick 310 includes a joystick shaft 312 that is attached to a hub, or wobble, 314.
The wobble 314 includes a groove 316. An O ring 318, which is made of urethane, is assembled onto the hub 314 and into the groove 316 thereof.
The hub 314, the groove 316, and the O ring 318 cooperate to provide means for attaching the joystick 310 to the housing 302, for centering the joystick 310, and for allowing the hub 314 to pivot as the joystick 310 is moved to a tilt angle, or a mechanical input, 320 with respect to X and/or Y
axes.
A smaller hub 322 provides means for piloting a spring 324, and a threaded plug 326 retains and preloads the spring 324. The preloaded spring 324 presses the hub 314 firmly against a counterbore shoulder 327, so that the spring 324, the hub 314, and the counterbore shoulder 327 provide means for centering the joystick 310 and its shaft 312 with respect to the intersection of the X and Y axes, the lamp 309, and the light-sensitive devices, 12A, 12B, 12C, and 12D.
The light-sensitive devices 12A, 12B, 12C, and 12D open into an enclosed chamber, or ambient light-excluding cavity, 328 that is formed by a 5 cylindrical bore 329. A mirrored surface, or reflective surface, 330 which may be a chrome plated surface of the hub 314, or a mirror attached to the hub 314 by any suitable means, reflects light from the lamp 309 to the photoresistors 12A, 12B, 12C, and 12D in accordance with selective positioning of the joystick 310 with respect to the X and Y axes.
10 The lamp 309, the mirrored surface 330, and the light-sensitive devices 12A, 12B, 12C, and 12D are positioned to develop substantially equal resistances in the light-sensitive devices 12A, 12B, 12C, and 12D which are each in parallel with a resistor, such as the resistors 14A and 14B of FIGURE

which also have equal resistances.
15 Since the X-Y input device 300 includes two of the light-sensitive voltage dividers 10 of FIGURE 1, when the joystick shaft 312 is centered at the intersection 277 of the X and Y axes, as shown in FIGURE 23, two null voltages are produced at the output nodes 18 of FIGURE 1 that are each one-half of the source voltage, one null voltage for each of the two light-sensitive voltage 20 dividers 10.
Movement of the joystick shaft 312 away from the intersection, or neutral position, 277 of the X and Y axes of FIGURE 23, and along the X axis, increases the light to one of the photoresistors, 12C or 12D, decreasing the resistance thereof, and decreases light to another of the photoresistors, 12D
or 25 12C, increasing the resistance thereof, thereby providing a signal voltage at the output node 18 of FIGURE 1 that is either greater or less than the null voltage.
The threaded plug 326 of the X-Y input device 300 includes a conical bore 332 that limits movement of the joystick shaft 312 with respect to the intersection 277 of the X and Y axes. Inspection of FIGURE 22 reveals that a large force could be placed on the joystick shaft 312 in any direction without causing damage other than bending the joystick shaft 312.
The lamp 309 is an LED that is manufactured by Lumex Opto Components, Inc. of Palatine, Illinois as part no. SSI LXR4815 GC 12V15.

The lamp 309 directs a focused light onto the mirrored surface 330, thereby enhancing the control of the light-sensitive devices 12A, 12B, 12C, and 12D by the mirrored surface 330, as opposed to a lamp that would disperse its light in many directions.
Referring now to FIGURE 24, a light-intensity control, or voltage control, 360 includes a P-channel MOSFET 362, and resistors 364 and 366 that are disposed in series with a switch 368 between a positive potential and ground. The resistors 364 and 366, the switch 368, and a capacitor 370 determine voltages applied to a gate G of the MOSFET 362, and a Zener diode 372 protects the gate G from excessive voltages.
The electric lamp 20 is connected directly to the positive potential and it is selectively connected to ground by an NPN transistor 374. The MOSFET
362 and a potentiometer 376 supply voltages to a base B of the NPN transistor 374 to control brightness of the lamp 20, as described below.
When the switch 368 is open, the gate G of the MOSFET 362 is high, the MOSFET 362 is open, the base B of the NPN transistor 374 is low, and the NPN transistor 374 is open, so that the lamp 20 is not energized.
When the switch 368 is closed, the resistors 364 and 366 form a voltage divider, and the difference in voltage between the source and a node 378 causes the capacitor 370 to charge, momentarily lowering the voltage in the node 378 below that normally determined by the resistors 364 and 366.
This drop in voltage at the node 378 and at the gate G of the MOSFET
362 causes the MOSFET 362 to conduct. As the voltage at the gate G is lowered and the MOSFET 362 conducts, a voltage is placed on the base B of the NPN transistor 374, so that the NPN transistor 374 controls voltage applied to the lamp 20 by providing a variable conductance between a collector C and an emitter E.
The voltage applied to the lamp 20 will be determined by selective positioning of a wiper 380 of the potentiometer 376, a resistor 382 that is in series with the potentiometer 376, and the capacitor 370. That is, immediately after the switch 368 is closed, the capacitor 370 will lower the voltage in the node 378 below that normally determined by the resistors 364 and 366, thereby increasing the voltage applied to the lamp 20 progressively. Thus, by selecting the value of the capacitor 370 in accordance with the values of the resistors 364 and 366, a soft start can be provided for electric motors and the conveyances that they propel, or for other devices requiring a soft start.
When the switch 368 is opened, the capacitor 370 discharges through the resistor 364, raising the voltage at the node 378 to the potential of the positive source, raising the voltage applied to the gate G of the MOSFET 362, and opening the MOSFET 362. Then the voltage applied to the base B of the NPN transistor 374 drops, the NPN transistor 374 opens, and the lamp 20 darkens. A soft stop can be provided for electric motors and conveyances that they propel, or for other devices requiring a soft stop, by selecting the capacity of the capacitor 370 in accordance with the resistance of the resistor 364.
As previously mentioned, selective positioning of the wiper 380, together with the resistor 382, determines voltages applied to the lamp 20.
That is, selective positioning of the wiper 380 determines voltages applied to the lamp 20, as limited by the resistor 382, irrespective of the voltage of the source.
For instance, nominally a 12 volt source is used, but the nominal voltage of the lamp 20 may be only 5 volts, so the resistor 382 is sized to allow the potentiometer to selectively control voltages applied to the lamp 20 within a suitable range.
Referring now to FIGURE 25, a light-intensity control, or voltage control, 390 for the lamp 20 includes an N-channel MOSFET 392. A drain D
of the MOSFET 392 is connected to a positive polarity of a source of voltage (not shown) via a resistor 394, and the lamp 20 is connected intermediate of a source S of the MOSFET 392 and a ground.
The switch 368 symbolizes one or more switches that may be actuated in any suitable manner by any suitable means to start and stop a motor or a conveyance. For instance, in U.S. Patent Application S/N 08/713,049, Lautzenhiser teaches starting a power wheelchair by voice or breath commands and stopping the wheelchair by one or more emergency shut-down switches.
Voltage for the gate G of the MOSFET 392 is enabled by the switch 368 and is selectively adjusted by positioning of a wiper 398 of a potentiometer 400. The potentiometer 400 is interposed between resistors 402 and 404, thereby providing a voltage divider circuit 406 in which wiper voltages may be selectively chosen within a range that is suitable for application to the gate G.
When the switch 368 is closed, a capacitor 408, which is connected in series with a resistor 410 between the wiper 398 and the ground, starts to charge, limiting a rate of increase of voltage applied to the gate G of the MOSFET 392, but slowly charging to a voltage selected by the wiper 398.
When the capacitor 408 is fully charged, voltage applied to the lamp 20 will be in accordance with selective positioning of the wiper 398.
This limiting of the increase in voltage applied to the gate G slows an increase in conductance of the MOSFET 392, slows an increase in voltage applied to the lamp 20, thereby slowing an increase in lumen output, slows an increase in sensitivity of the light-sensitive voltage divider 10 of FIGURE 1, thereby slowing an increase in sensitivity of the X-Y input device 110, 150, 182, 240, or 300 of FIGURES 9-23, and thereby providing soft starts.
When the switch 368 is opened, perhaps in response to an emergency situation as taught by Lautzenhiser in U.S. Patent 5,635,807, the capacitor discharges, not only through the resistor 410, but also through a resistor 412 that is connected in series with a diode 414.
Thus, the capacitor 408 discharges more quickly than it charges, voltage at the gate G reduces more rapidly than it increases, light intensity of the lamp 20 decreases more rapidly than it increases, the sensitivity of the two light-sensitive voltage dividers 10 of the X-Y input device, 110, 150, 182, 240, or 300, decreases more rapidly than it increases, and shut-down is more rapid than start-up. And yet, while slowing of a conveyance (not shown) can be made relatively rapid, the rate of slowdown can still be limited to a safe value.
The N-channel MOSFET 392 is an enhancement mode device, and preferably is part number TN0104NE, manufactured by Supertex, Inc. of Sunnyvale, California. Suitable values for the other components are: the resistor 394 = 56 ohms; the potentiometer 400 = 10K ohms; the resistor 402 = 82.5K ohms; the resistor 404 = 68K ohms; the capacitor 408 = 1.0 microfarad; the resistor 410 = 249K ohms; and the resistor 412 = 100K ohms.
A change in sensitivity of the light-sensitive voltage dividers of FIGURES 1-8, and a similar change in sensitivity of an input device of FIGURES

3-23 in which they are used, can be achieved by changing the voltage applied to the electric lamp 20 by any suitable means, such as the light-intensity controls of FIGURES 24 or 25 which, optionally, are included in each of the five X-Y input devices of FIGURES 3-23.
The headband 184 provides means for tilting the housing 186 of the X-Y input device 182; the intersection 277 of the X and Y axes is in a neutral position for the joystick shafts 262 and 312; the input device 182 is in its neutral position 227 of FIGURE 15 when the tilt angle 226 of FIGURE 16 is equal to zero; and the voltage dividers of FIGURES 1-8 have positive and ground input nodes.
The joystick X-Y input devices, 110 of FIGURES 9-10 and 240 of FIGURES 17-21, can be characterized as having a dark null, because, the light-control cap, 117 or 246, occludes light from being transmitted from the lamp, 114 or 206, to any of the light-sensitive devices, 74 or 12A-12D, when the joystick, 118 or 244, is in a neutral position, as shown in FIGURES 9 and 17.
As can be seen in FIGURES 11 and 15, when the tilt-actuated X-Y input devices, 150 and 182, are in the neutral positions shown, the light-restricting fluid, 162 or 212, partially, and equally, covers the light-sensitive devices, 74 or 12A-12D, so that the light-sensitive devices, 74 or 12A-12D, receive equal quantities of light. Therefore, because of the preferred level of the fluid, 162 or 212, the tilt-actuated X-Y input devices, 150 and 182, each can be characterized as having a light null.
In like manner, it can be seen by inspection that the joystick X-Y input device 300 of FIGURE 22 also has a light null.
In FIGURES 9 and 17, the light-control cap, 117 or 246, provides means for controlling transmission of light. In FIGURE 22, the mirrored surface 330 provides means for controlling transmission of light, and in FIGURES 11 and 15, the fluid, 162 or 212, provides means for controlling transmission of light.
In the light-sensitive voltage divider 26 of FIGURE 2, two resistive devices are connected in series. One of these resistive devices is the light-sensitive device 12A, and the other resistive device is the resistor 28.

The resistors, 14A and 14B, or 54, provide a more positive null for the light-sensitive voltage dividers, 10, 46A, 72A, 92A, and 102A, than would be provided by the light-sensitive devices, 12A-12D, 48, 74, or 94, alone.
While light-sensitive voltage dividers, some of which can be classified 5 as null-balanced light sensors, have been shown and described, other voltage-dividing circuits, and other null-balanced light sensors may be used without departing from the scope of the present invention.
All five X-Y input devices, 110, 150, 182, 240, and 300 of FIGURES 9-23 may be constructed using any two of the light-sensitive voltage dividers of 10 FIGURES 1-8.
However, if only one of the light-sensitive voltage dividers of FIGURES
1-8 is used in any of the embodiments of FIGURES 9-23, all the five embodiments of FIGURES 9-23 become single-axis input devices, 420, 422, 424, 426, and 428, respectively. Further, the input devices 422 and 424, of 15 FIGURES 11-13 and 14-16 become single-axis tilt-actuated input devices.
That is, while the use of light-sensitive devices have been shown and described with X-Y input devices, in a more basic form, the present invention provides an input device in with only one mechanical input, that produces only one electrical output, whether the input be by mechanically positioning a 20 device such as a joystick, or by mechanically positioning a tilt angle.
While photoresistors, phototransistors, photodiodes, and any other suitable light-sensitive devices may be used without departing from the scope of the present invention, phototransistors are preferred.
With regard to advantages of the present invention, the light-sensitive 25 input devices of FIGURES 9-23 have excellent resolution, minimal stiction, minimal hysteresis, and definite light and/or dark nulls. They are adaptable for use with a large range of input voltages, and they have the ability to produce a large range of output signals.
They have little tendency to overshoot or oscillate, so they are usable 30 with minimal electronic damping. They are insensitive to both RFI and EMI
interference, and they do not produce any RFI or EMI fields that could interfere with sensitive electronic equipment.

Further, the input devices of the present invention provide selectable sensitivity, selectable rate of start-up, and selectable rate of shut-down.
Additionally, the present invention provides means for selectively adjusting quadrant sensitivity either mechanically or electrically in both the tilt-actuated X-Y input devices, 150 and 182, and the joystick X-Y input devices, 110, 240, and 300.
Quadrant sensitivity can be adjusted mechanically by quadrant distortion, as described in conjunction with FIGURES 18-21. Quadrant sensitivity also can be adjusted by selective vertical positioning of the light sensitive devices, 12A, 48, 74, or 94, as illustrated by the deadband 283 of FIGURE 17A.
If one or more light-sensitive devices, 12A and/or 12B of one light-sensitive voltage divider 10, is/are positioned vertically from a light-sensitive device, 12C or 12D of a second light-sensitive voltage divider 10, not only are different deadbands provided with regard to separate axes, X or Y, but also the maximum light transmitted to one of the light-sensitive devices, 12A, 12B, 12C, or 12D, is reduced, thereby selectively changing sensitivity of the X-Y input device, 110, 150, 182, 240, or 300 with regard to one axis, X or Y.
Further, quadrant sensitivity of the X-Y input devices, 110, 150, 182, 240, or 300 can be adjusted electrically as taught in FIGURE 8. That is, selective adjustment of one or both of the trim potentiometers 104 of one of the light-sensitive voltage dividers, 102A or 102B, selectively adjusts both the proportionality and the maximum output of one or both of the light-sensitive devices 48 of that light-sensitive voltage divider, 102A or 102B.
The input devices are usable over a wide range of ambient temperatures, avoid using mechanical-electrical components such as potentiometers, each one is so light in weight that a person will forget that it is on one's head, and so compact that it can be hidden in one's hair.
As an example of the long life and dependability of the input devices of the present invention, the lamp 206 has a life expectancy of 40,000 hours when energized with 5 volts ac, and in the present design, less than 2 volts do is used. In like manner, LED's, such as the lamp 309, have extensive life expectancies.

While specific apparatus and method have been disclosed in the preceding description, and while part numbers have been inserted parenthetically into the claims to facilitate understanding, it should be understood that these specifics have been given for the purpose of disclosing the principles of the present invention, and that many variations thereof will become apparent to those who are versed in the art. Therefore, the scope of the present invention is to be determined by the appended claims without any limitation by the part numbers inserted parenthetically therein.
Industrial Applicability The present invention is applicable to devices in which it is desirable to produce an electrical signal in response to a mechanical input with respect to a single axis or two electrical outputs in response to X-Y mechanical inputs, whether the mechanical inputs are made by actuation of joystick, or lever, or by tilting a housing.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. An input device (420, 422, 424, 426, or 428) which comprises:
a null-balanced light sensor (10);
a source (20, 114, 158, 206, or 309) of light; and means (117, 162, 212, 246, or 330) for controlling transmission of said light from said source to said null-balanced light sensor proportional to a mechanical input (134, 166, 226, 281, or 320).

2. A tilt-actuated input device (422 or 424) which comprises:
a housing (152 or 186) having an enclosed chamber (168 or 204);
a first light-sensitive device (12A, 48, 74, or 94) being disposed with respect to a first axis, being operatively attached to said housing, and being in light-receiving communication with said enclosed chamber;
a source (20, 158, or 206) of light being operatively attached to said housing, and being in light-transmitting communication with said first light-sensitive device through said enclosed chamber; and means (162 or 212) for controlling said transmission of light from said source to said first light-sensitive device proportional to tilting of said housing with respect to a second axis.

3. A joystick X-Y input device (110, 240, or 300) which comprises:
a housing (112, 242, or 302) having an enclosed chamber (126, 261, or 328);
a first light-sensitive voltage divider (10 or 26) being disposed with respect to a first axis, being operatively attached to said housing, and being in light-receiving communication with said enclosed chamber;
a second light-sensitive voltage divider (10 or 26) being disposed with respect to a second axis, being operatively attached to said housing, and being in light-receiving communication with said enclosed chamber;
a source (20, 114, 206, or 309) of light being operatively attached to said housing, and being in light-transmitting communication with said first and second light-sensitive voltage dividers through said enclosed chamber;

means (117, 246, or 330) for controlling transmission of said light from said source to respective ones of said first and second light-sensitive voltage dividers proportional to an input with respect to an X-Y input; and a joystick (118, 262, or 310) being operatively attached to said means for controlling, and being pivotally moveable with respect to said X and Y
axes.

4. A tilt-actuated X-Y input device (150 or 182) which comprises:
a housing (152 or 186) having an enclosed chamber (168 or 204);
a first light-sensitive voltage divider (10 or 26) being operatively attached to said housing, being oriented with respect to a first axis, and being in light-receiving communication with said enclosed chamber;
a second light-sensitive voltage divider (10 or 26) being operatively attached to said housing, being oriented with respect to a second axis; and being in light-receiving communication with said enclosed chamber;
a source (20, 158, or 206) of light being operatively inserted into said housing, and being in light-transmitting communication with said first and second light-sensitive voltage dividers through said enclosed chamber; and means (162 or 212) for controlling transmission of said light from said source to said light-sensitive voltage dividers proportional to tilting of said housing with respect to said X and Y axes.

5. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which said input device produces a null output in the absence of light produced by said source of light.

6. An input device (150 or 182) as claimed in Claim 2 in which said input device produces a null output in the absence of light produced by said source of light.

7. An input device (110, 240, or 300) as claimed in Claim 3 in which said input device produces a null output in the absence of light produced by said source of light.

8. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which:
said source of light comprises an electric lamp (20, 114, 158, 206, or 309) and means (117, 162, 212, 246, or 300) for controlling a voltage supplied to said electric lamp;
said controller produces a null output in the absence of a voltage supplied to said electric lamp; and said input device further comprises means (368) for isolating said electric lamp from said voltage.

9. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which said input device comprises means (117, 162, 212, 246, or 300) for selectively adjusting said proportionality.

10. An input device (150 or 182) as claimed in Claim 2 in which said input device comprises means (380 or 398) for selectively adjusting said proportionality.

11. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which:
said source of light comprises an electric lamp (20, 114, 158, 206, or 309); and said input device includes means, comprising means (360 or 390) selectively adjusting a voltage supplied to said electric lamp, for selectably controlling said proportionality.

12. An input device (110, 240, or 300) as claimed in Claim 3 in which:
said source of light comprises an electric lamp (20, 114, or 309); and said input device includes means, comprising means (360 or 390) selectively adjusting a voltage supplied to said electric lamp, for selectably controlling said proportionality.

13. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which:
said source of light comprises an electric lamp (20, 114, 158, 206, or 309) and means for supplying a voltage to said electric lamp; and said input device further comprises means (370 or 408) for effecting a controlled decrease in said voltage supplied to said lamp; whereby both a soft shut-down of said lumens produced by said source of light and a soft shutdown in said proportionality are provided.

14. An input device (110, 240, or 300) as claimed in Claim 3 in which:
said source of light comprises an electric lamp (20, 114, or 309) and means for supplying a voltage to said electric lamp; and said input device further comprises means (370 or 408) for effecting a controlled decrease in said voltage supplied to said lamp; whereby both a soft shut-down of said lumens produced by said source of light and a soft shutdown in said proportionality are provided.

15. An input device (110, 150, 182, 240, or 300) as claimed in Claim 1 in which:
said source of light comprises an electric lamp (20, 114, 158, 206, or 309) and means for supplying a voltage to said electric lamp; and said input device comprising means (370 or 408) for effecting a controlled increase in said voltage supplied to said electric lamp; whereby both a soft start-up of said lumens produced by said source of light and a soft start-up in said proportionality are provided.

16. An input device (110, 240, or 300) as claimed in Claim 3 in which:
said source of light comprises an electric lamp (20, 114, or 309) and means for supplying a voltage to said electric lamp; and said input device comprising means (370 or 408) for effecting a controlled increase in said voltage supplied to said electric lamp; whereby both a soft start-up of said lumens produced by said source of light and a soft start-up in said proportionality are provided.

17. An input device (110, 240, or 300) as claimed in Claim 3 in which said first light-sensitive voltage divider (10) comprises:
first and second input nodes; (+ and gnd.) an output node (18);
a first light-sensitive device (12A, 48, 74, or 94) that is connected between said first input node and said output node; and a second light-sensitive device (12B, 48, 74, or 94) that is connected between said output node and said second input node.

18. An input device (150 or 182) as claimed in Claim 4 in which said first light-sensitive voltage divider (10) comprises:
first and second input nodes; (+ and gnd.) an output node (18);
a first light-sensitive device (12A, 48, 74, or 94) that is connected between said first input node and said output node; and a second light-sensitive device (12B, 48, 74, or 94) that is connected between said output node and said second input node.

19. An input device (110, 240, or 300) as claimed in Claim 3 in which said first light-sensitive voltage divider (10) comprises:
first and second input nodes; (+ and gnd.) an output node (18);
a first light-sensitive device (12A) that is connected between said first input node and said output node;
a second light-sensitive device (12B) that is connected between said output node and said second input node; and first and second resistors (14A and 14B) that are connected in parallel with respective ones of said light-sensitive devices.

20. An input device (150 or 182) as claimed in Claim 4 in which said first light-sensitive voltage divider (10) comprises:
first and second input nodes; (+ and gnd.) an output node (18);

a first light-sensitive device (12A) that is connected between said first input node and said output node;
a second light-sensitive device (12B) that is connected between said output node and said second input node; and first and second resistors (14A and 14B) that are connected in parallel with respective ones of said light-sensitive devices.

21. An input device (110 or 240) as claimed in Claim 1 in which said means for controlling transmission of said light comprises a light-control cap (117 or 246) that is disposed over said source of light (114 or 206).

22. An input device (110 or 240) as claimed in Claim 3 in which said means for controlling transmission of said light comprises a light-control cap (117 or 246) that is disposed over said source of light (114 or 206).

23. An input device (300) as claimed in Claim 1 in which said means for controlling said transmission of light comprises:
a reflective surface (330); and means (310), being operatively connected to said reflective surface, for moving said reflective surface.

24. An input device (300) as claimed in Claim 3 in which said means for controlling said transmission of light comprises:
a reflective surface (330); and means (310), being operatively connected to said reflective surface, for moving said reflective surface.

25. An input device (150 or 182) as claimed in Claim 1 in which said means for controlling said transmission of light comprises a fluid (162 or 212).

26. An input device (150 or 182) as claimed in Claim 2 in which said means for controlling said transmission of light comprises a light-restricting fluid (162 or 212).

27. An input device (150 or 182) as claimed in Claim 4 in which said means for controlling said transmission of light comprises a light-restricting fluid (162 or 212).

28. An input device as claimed in Claim 2 in which said means for controlling said transmission of light comprises a light-blocking fluid (162 or 212).

29. An input device (150, 182, or 300) as claimed in Claim 1 in which said input device includes a neutral position (164 or 227) wherein said means for controlling continues to transmit said light.

30. An input device (150 or 182) as claimed in Claim 2 in which said input device includes a neutral position (164 or 227) wherein said means for controlling continues to transmit said light.

31. An input device (300) as claimed in Claim 3 in which said input device includes a neutral position wherein said means for controlling continues to transmit said light.

32. An input device (110 or 240) as claimed in Claim 1 in which said input device includes a neutral position wherein said means for controlling said transmission occludes said transmission of light.

33. An input device (110 or 240) as claimed in Claim 3 in which said input device includes a neutral position wherein said means for controlling said transmission occludes said transmission of light.

34. An input device (240) as claimed in Claim 1 in which said input device further comprises a dead band (283) wherein said transmission of light is prevented.

35. An input device (240) as claimed in Claim 3 in which said input device further comprises a dead band (283) wherein said transmission of light is prevented.

36. An input device (110, 240, or 300) as claimed in Claim 3 in which said input device further comprises means (104, 283, or 284-289) or for making a sensitivity with regard to one of said axes (X or Y) greater than a sensitivity of the other of said axes (X or Y).

37. An input device (150 or 182)) as claimed in Claim 4 in which said input device further comprises means (104, 283, or 284-289) for making a sensitivity with regard to one of said axes (X or Y) greater than a sensitivity of the other of said axes (X or Y).

38. A light-sensitive voltage divider (10, 26, 46A, 72A, 92A, or 102A) which comprises:
first and second input nodes; (+ and gnd.) an output node (18, 38, or 52A);
a first resistive device (12A, 14A, 48, 74, or 94) being connected to said first input node and said output node;
a second resistive device (12B, 14B, 28, 48, 74, or 94) being connected to said second input node and to said output node; and one of said resistive devices comprises a first light-sensitive device (12A, 12B, 48, 74, or 94).

39. A light-sensitive voltage divider (10, 46A, 72A, 92A, or 102A) as claimed in Claim 38 in which the other of said resistive devices comprises a second light-sensitive device (12B, 12A, 48, 74, or 94).

40. A light-sensitive voltage divider (26) as claimed in Claim 38 in which said light-sensitive voltage divider comprises a variable resistor (32) that is connected in parallel with said one light-sensitive device (12A).

41. A light-sensitive voltage divider (10, 46A, 72A, 92A, or 102A) as claimed in Claim 38 in which:
the other of said resistive devices comprises a second light-sensitive device (12B, 12A, 48, 74, or 94); and said light-sensitive voltage divider further comprises first and second resistors (14A and 14B) that are connected in parallel with said first and second light-sensitive devices (12A, 12B, 48, 74, or 94).

42. A light-sensitive voltage divider (26) as claimed in Claim 38 in which the other of said resistive devices comprises a variable resistor (28).

43. A light-sensitive voltage divider (10, 26, or 72A) as claimed in Claim 38 in which said first light-sensitive device comprises a phototransistor (12A or 74).

44. A method for producing an electrical output in response to a tilt-angle input, which method comprises:
a) providing a source of light in an enclosed chamber;
b) exposing a light-sensitive device to said source of light through said enclosed chamber; and c) controlling transmission of said light from said source to said light-sensitive device as a function of said tilt-angle input.

45. A method as claimed in Claim 44 in which said controlling step comprises disposing a light-restricting fluid in said chamber.

46. A method as claimed in Claim 44 in which said method further comprises providing a null-output in the absence of said source of light.

47. A method as claimed in Claim 44 in which said controlling step includes:

a) actuating to a neutral position; and b) transmitting said light substantially equally to two light-sensitive devices in response to said actuating step.

48. A method as claimed in Claim 44 in which said controlling step includes:
a) actuating to a neutral position; and b) occluding transmission of light to light-sensitive device in response to said step of actuating to said neutral position.

49. A method for producing an electrical output in response to a mechanical input, which method comprises:
a) providing a source of light in an enclosed chamber;
b) exposing a light-sensitive voltage divider to said source of light through said enclosed chamber; and c) controlling transmission of said light from said source to said light-sensitive device as a function of said mechanical input.

50. A method as claimed in Claim 49 in which said controlling step comprises covering said source of light.

51. A method as claimed in Claim 49 in which said controlling step comprises covering said source of light.

52. A method as claimed in Claim 49 in which said controlling step comprises reflectively controlling.

53. A method as claimed in Claim 49 in which said method further comprises providing a null-output in the absence of said source of light.

54. A method as claimed in Claim 49 in which said controlling step includes:

a) actuating to a neutral position; and b) transmitting said light substantially equally to two light-sensitive devices in response to said actuating step.

55. A method as claimed in Claim 49 in which said controlling step includes:
a) actuating to a neutral position; and b) occluding transmission of light to light-sensitive device in response to said step of actuating to said neutral position.