United States Patent|119)
`[11] Patent Number:
`4,649,323
`[45] Date of Patent: Mar. 10, 1987—
`Pearlmanetal.
`
`[54]
`
`[75]
`
`[73]
`
`(21)
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`[22]
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`[51]
`[52]
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`[58]
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`[56]
`
`MICROCOMPUTER-CONTROLLED LIGHT
`SWITCH
`
`Inventors: Gordon W. Pearlman; Steven B.
`Carlson, both of Portiand, Oreg.
`Lightolier Incorporated, Jersey City,
`N.J.
`
`Assignee:
`
`Appl. No.: 724,015
`Filed:
`Apr. 17, 1985
`
`int, Ch! o.seesescssssressesssersennessenseeenees HO5B 37/02
`US. Cl. ceeseesssssesseersceensnstenenes 315/307; 315/292;
`315/293; 315/362
`Field of Search................ 315/307, 292, 293, 362
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`6/1972 ISAAC ...sssssssserecsesseereeseneonses 315/292
`3,668,467
`3,706,914 12/1972 Van Buren....
`. 315/316
`3,766,431 10/1973 Isaacs. .......0
`w. 315/292
`3,805,096 4/1974 Hamilton ..
`we 315/292
`3,968,401
`7/1976 Bryant.......
`w 315/292
`4,240,011 12/1980 Dinges ......
`4,241,295 12/1980 Williams .......ssssssoerernsreses 315/294
`4,287,468
`9/1981
`Sherman...
`315/DIG.4
`4,289,972 9/1981 WELD crressesscserssesreeerssesonsneens 315/362
`4,359,670 11/1982 Hosaka et al.
`.......---..srseo 315/307
`
`ve 315/293
`
`
`
`Primary Examiner—Harold Dixon
`Attorney, Agent, or Firm—Chernoff, Vilhauer, McClung
`& Stenzel
`
`ABSTRACT
`[57]
`A light level controller includes a microcomputer con-
`trolled light switch which responds to a manual tap or
`a longer manual depression of the switch in order to
`initiate various control modesfor a light source. Preset
`levels of light intensity may be stored in the microcom-
`puter’s memory and an automatic fade mode may be
`initiated to cause the level of light intensity to fade from
`a current level to a preset level at a pre-established rate.
`The controller may respond to the momentary depres-
`sion of the switch to initiate the automatic fade mode or
`if tapped while a fade is in progress it may cause the
`light source to make an abrupttransition to either full
`on or full off, depending on whether a higher or lower
`level of light intensity is desired. A depression of the
`switch for a period longer than a tap will cause the level
`oflight intensity to continue to change until the switch
`is released, and simultaneously this level will be stored
`in memory.
`
`21 Claims, 8 Drawing Figures
`
`|6rowenPOWERLa
`
`AC MAINS
`(20V 60
`CYCLE AC
`
`30b COMPUTER
`
`ee
`LED DISPLAY
`
`RECTIFIER
`AND CLAMP
`CPOSITIVED
`RECTIFIER
`AND CLAMP
`CNEGATIVE)
`
`MICRO
`
`RESET
`NETWORK
`
`1
`
`APPLE 1026
`
`1
`
`APPLE 1026
`
`

`

`US. Patent Mar. 10, 1987
`
`Sheet 1 of3
`
`4,649,323
`
`
`
`AC MAINS
`i20V 60
`
`
`
`DC POWER
`SUPPLY
`
`FIG.|
`
`CYCLE AC
`
`
`
`ZERO CROSSING
`DETECTOR
`
`
`
`
`
`
`RECTIFIER
`AND CLAMP
`
`
`CPOSITIVE)
`MICRO
`
`
`
`COMPUTER
`
`
`RECTIFIER
`
`
`AND CLAMP
`
`
`0
`CNEGATIVE)
`
`
`
`
`
`
`
`teNETWORK
`
`AC LINE
`
`I2z0V ZERO
`
`CROSS
`
`FIRING SIGNAL
`FROM MICROCOMPUTER
`
`|
`
`LOAD
`VOLTAGE
`
`70°
`
`2
`
`

`

`U.S. Patent Mar. 10, 1987
`
`Sheet 2 of 3
`
`4,649,323
`
`
` ezAipoony
`
`EZ
`SISAL
`
`
`
`
`
`
`|ZaIPE
`LLL
`NISSSSS>
`<r
`
`VNveb<a
`
`3
`
`
`
`
`
`
`
`
`

`

`U.S. Patent Mar. 10,1987
`
`Sheet 3 of3
`
`4,649,323
`
`C= CURRENT LEVEL
`
`N= NEW LEVEL
`P= PRESET
`LEVEL
`
`°
`
`
`
`
`
`F | G. 4b
`
`C= CURRENT LEVEL
`N= NEW LEVEL
`P= PRESET
`LEVEL
`
`
`
`
`INCREMENT
`N=C
`
`DECREMENT
`
`N=C
`P=C
`
`
`
`
`
`
`FIG.4a
`C= CURRENT LEVEL
`N= NEW LEVEL
`P= PRESET
`LEVEL
`
`4
`
`

`

`1
`
`4,649,323
`
`MICROCOMPUTER-CONTROLLED LIGHT
`SWITCH
`
`2
`3,706,914; and Isaacs, U.S. Pat. Nos. 3,766,431 and
`3,668,467.
`SUMMARYOF THE INVENTION
`
`5
`
`40
`
`BACKGROUNDOF THE INVENTION
`
`The present invention provides a highly versatile
`microcomputer-controlled light level intensity switch
`The present invention relates to a manually operated
`which is operated by a pair of non-latching switches
`switch such as a wall-mountedlight switch for control-
`which provide inputs to the microcomputer. The non-
`ling the level oflight intensity fromalight fixture and
`latching switches may be arranged as upper and lower
`more particularly to a light level controller actuated by
`switches on a rocker panel or independentpair of panels
`the switch which includes a microcomputer forinitiat-
`which are normally biased to remain in a neutral posi-
`ing control programsto regulate the level oflight inten-
`tion. The switches are each connected in series with the
`sity.
`AC mains powerline so that when either switch is
`Wall-mounted light switches which include a dimmer
`depressed a signal in the form ofa series of sequential
`have becomeincreasingly popular especially for resi-
`pulses is provided to the microcomputer.
`dential applications whereit is desired to precisely con-
`When the switch is depressed in either the up or
`trol the level of light intensity in a particular room.
`down direction,
`the microcomputer first determines
`Such light switches usually include a variable resistor
`whetherthe depression ofthe switch is momentary, that
`which is manually manipulated to control the voltage
`is, a brief tap, or whetherit is being held down for a
`input to the light, where the variable resistor is con-
`period of more than transitory duration. When the
`nected in series with the household AC powerline. A
`switch is held, the microcomputer advances the level of
`desirable feature in such switches would be the ability
`light intensity in the direction indicated by the switch,
`to return to predetermined levels of light intensity from
`that is, either towards bright or towards dim. When the
`conditionsofeither full power on orfull power off. At
`switch is subsequently released the microcomputer
`present, however, such switches have no such memory
`stores that current level of light intensity as a “‘preset”
`and formerly established light intensity levels may be
`level in its memory. If the switchis first tapped in either
`reestablished only by manual operation and guesswork.
`direction with the light intensity at somestatic level the
`Thereare in existence, however, touch actuated dim-
`microcomputer will cause the level of light intensity to
`mer controls which cycle through a dim to a bright
`automatically advance or “fade” towards a predeter-
`eycle and back again, and include a memory function
`mined level, either “full on,” “off,” or “preset.” The
`such that removing the hand from the switch will stop
`fade may occur at a rate which can be programmedin
`the cycle and store the level of light intensity at that
`the microcomputer. If desired, the speed of the fade
`point in memory. A subsequenttouch will turn the light
`may vary depending upon whetherthe fadeis from dim
`off and yet a further touch will return the lightto its
`to bright or vice versa. For example, it is possible to
`previous intensity level based upon the value of the
`program all downward fades to occur more gradually
`intensity level stored in memory. While an improve-
`than all upward fades. If the switch is tapped again
`ment over the manually-operated variable-resistor type
`while the light intensity is fading towards the preset
`of dimmer, this dimmer may require the user to manu-
`level, the microcomputer will halt the fade and cause
`ally cycle through a complete cycle of dim light to
`the light intensity level to abruptly shift to the preset
`bright light to arrive at a desired intensity level. This
`level. If the “up” switch is tapped with light at the
`latter switch is known as a DECORA ® touch dimmer
`preset level, the light intensity will fade to full maxi-
`and is manufactured by Leviton Manufacturing Com-
`mum.Ifit is tapped in the downward position when the
`pany, Inc. of Littleneck, N.Y. The DECORA ® touch
`light intensity level is at the preset position the light
`dimmer, however, lacks the versatility needed for cer-
`intensity will fade towards zero. Thus, the microcom-
`tain aesthetic effects such as an automatic gradual fade
`puter interprets the character of the command,thatis, a
`from one light level. to another. Moreover, it cannot
`hold or a tap, determines the current control mode, and
`changethe direction, that is, either the increasing (up)
`initiates a light intensity control function accordingly.
`or the decreasing (down), of light intensity from one
`The three types of programs are preset, automatic fade,
`direction to another without completing a full cycle
`and abrupt transition.
`from dim to bright and back again. Also, the touch
`The non-latching switches provide a pulse input,
`which is derived from the AC powersource, to the
`dimmer has no “remote” capability that would enable
`oneto use its features from a remote location such as a
`light switch through a clamp and half-waverectifying
`network. Thus, the input to the microcomputer is a
`haliway or another room. Full function remotes are
`series of square wave pulses. The microcomputer has an
`common with ordinary two-position light switches, but
`have not been available for dimmers because of the
`internal program which counts the numberof a sequen-
`tial series of pulses to determine if the switch is being
`complexity of the circuitry.
`tapped or held and executes a control program mode
`Yet another touch-type light control is shown in
`Hamilton, U.S. Pat. No. 3,805,096, and in Hosaka, etal.,
`accordingly,
`The microcomputer is connected to a source of light
`U.S. Pat. No. 4,359,670. These devices are responsive to
`such as an incandescent light bulb of between 40 and
`the duration oftouchforinitiating various control func-
`2,000 watts by means of a thyristor solid state switch.
`tions but include no provision for automatically fading
`The thyristor controls power to the incandescentlight
`light from one level to another.
`source by turning on at a predetermined phase angle
`Automatic fading has in the past been available only
`relative to the phase of the AC line source. For this
`in theatrical lighting systems employing very compli-
`purpose the thyristor is responsive to a timed firing
`cated switching inputs such as keyboard commands or
`signal generated by the microcomputer according to
`elaborate banks of switches. Examples of such systems
`the program in operation. The firing signal is synchro-
`are shownin Williams, U.S. Pat. No. 4,241,295; Dinges,
`nized with the incoming powersupply line by a zero
`et al., U.S. Pat. No. 4,240,011; Van Buren, U.S. Pat. No.
`
`35
`
`60
`
`65
`
`5
`
`

`

`4,649,323
`
`20
`
`25
`
`FIG. 1 is a schematic block diagram of a circuit con-
`structed according to the present invention.
`FIG.2 is a side view of a wall switch mounting con-
`taining the circuit of the present invention illustrated in
`FIG. L
`FIG.3 is a front view of an alternate type of wall
`switch mounting.
`FIG. 3(@) is a side view of the wall switch mounting
`of FIG.3.
`FIG. 4 is a flow chart diagram depicting the method
`of operation of the circuit illustrated in FIG. 1.
`FIG. 4(@) is a continuation of a portion of the flow
`chart diagram of FIG.4.
`FIG. 4(6) is a further continuation of the flow chart
`diagram of FIG.4.
`FIG. 5 is a waveform diagram illustrating the method
`of controlling the line voltage input to a light source
`using the circuit of FIG. 1
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`4
`3
`A still further object of this invention is to provide a
`crossing detector which detectsthe transition in the AC
`light level controller havingaplurality of light control
`powerline from positive to negative. The microcom-
`modesin which the particular mode chosen is a function
`puter receives the zero crossing information and syn-
`chronizes this information with its internal clock which
`of the period of time that the non-latching control
`switch is pressed.
`controls the timingofthe firing signal for the thyristor.
`A further object of this invention is to provide a light
`In this way the timing of the thyristor firing signal is
`level controlier in a wall switch mounting having a
`calibrated to the desired level of light intensity and
`visual indication of the intensity of the light on the
`represents a phase angle at which the AC line is gated
`room.
`into the incandescent light source.
`A still further object of this invention is to provide a
`Wheneither the “up” or “down” switch is held the
`wall-mounted light level controller having full remote
`computer first determines the current level of light
`intensity. The microcomputer then causes the level of
`capability.
`The foregoing and other objectives, features and
`light intensity to increase for “up” or decrease for
`advantagesofthe present invention will be morereadily
`“down” in predetermined increments by initiating thy-
`understood upon consideraton of the following detailed
`ristor firing signals which either advance the phase
`description of the invention taken in conjunction with
`gating of the AC waveorretard it. As long as either
`the accompanying drawings.
`switch is held “on,” the level of light intensity will
`gradually advance or decline. Each time an additional
`BRIEF DESCRIPTION OF THE DRAWINGS
`incrementoflight intensity is added it replaces the cur-
`rent level in the memory which continuesto be sampled
`in a closed-loop fashion until the switch is released.
`Whenthe switch is released the current level oflight
`intensity is stored in memory as a “preset”level.
`When either switch is tapped the microcomputer
`interrogates memory to find out if the current levelis
`equal to the preset level. This determines whether a
`fade is in progress or whetherthe lightintensity is not
`changing. The subsequent control modes, “fade” and
`“abrupt transition,” then depend upon whether the new
`level
`in memory is preset, full on, or full off, and
`whetherthe current level is higher than, lower than, or
`equal to this level.
`The switches are wired in line with the main 120-volt
`ACline. Since the switchesare at all times either “‘on”
`or “off” and there are no variable resistors used for the
`dimmingfunction,a parallel set of remote switches, also
`wired in line with the AC line, may be provided to give
`full remote capability. Thus, another switch box may be
`provided in a hallway or adjacent room which fully
`duplicates the functions of the primary switch box with-
`out the necessity for duplication of the microcomputer
`and its associated circuitry. The remote switches are
`wired in parallel with the primary switches through
`their wall-mounted switch box forming a second paral-
`lel input to the microcomputer.
`A primary object of this invention is to provide a
`light level controller which provides a maximum de-
`gree of flexibility in altering levels of light intensity
`according to the desires of the user.
`A further object of this invention is to provide a light
`level controller which includes an automatic fader for
`gradually fading the light intensity level from a current
`level to a preset level.
`Yet a further object of this invention is to provide a
`light level controller having means for manually over-
`riding the automatic fader and for making abrupttransi-
`tions in light level intensity from a current level to a
`predetermined level.
`A still further object of this invention is to provide a
`light level controller having the above features which
`can be mounted within a standard wall switch panel box
`and connected to a standard 60-cycle AC household
`powersupply.
`Yet a further of this invention is to provide a light
`level controller in a wall switch mounting which is
`microcomputer-controlled and responsive to the state
`of non-latching switches which provide a digital input
`signal to the microcomputer.
`
`A light source 10 which may be, for example, an
`incandescent
`light source drawing between 40 and
`2,000 watts of power, is connected to a source of AC
`power12 througha thyristor 14. The AC source 12 is a
`standard household power supply, 60-cycle, 120-volt
`AC. Thethyristor 14 is a bi-directional SCR controller.
`Thecontrol line 11 for the thyristor 14 is connected to
`a microcomputer 16. The microcomputer 16 is powered
`by a DC powersupply 18 and includes an input from a
`zero crossing detector 20 whichis also connected to AC
`powersource 12. A wall switch mounting 22 (enclosed
`within the dotted line in FIG. 1) may include a pair of
`nonlatching switches 24a and 245 and an LED display
`26. The LED display may be connected to the mi-
`crocomputer 16 by a bus 28 which may include any
`desired plurality of lines. In the example shown in FIG.
`1, line 28 is an eight line bus. Each of the nonlatching
`switches 24a and 246 includes a rectifier and clamp
`circuit 30a and 308, respectively, which provide half-
`waverectification and voltage clamping. The switches
`24a and 24b are connected to AC power source 12
`through a resistor 17 and diodes 13 and 15. The output
`of the rectifier and clamp circuits 30a and 306 are con-
`nected as inputs to microcomputer 16. Microcomputer
`16 also includes a clock which may, for example, be a
`crystal oscillator 32. The microcomputer 16 also in-
`cludes as an input, a reset network 34. A remote input
`19 mayalso be providedas a parallel input to circuts 30a
`
`30
`
`45
`
`60
`
`65
`
`6
`
`

`

`4,649,323
`
`5
`
`15
`
`25
`
`35
`
`5
`and 304. Remote input 19is in all respects identical to
`the network of switches 24a and 246 including resistor
`17 connected to the AC line and diodes 13 and 15. Thus,
`either the wall mounting 22 or the remote input 19 may
`initiate the functions discussed herein.
`Between thyristor 14 and light source 10 there is a
`choke or induction coil 36 which provides current
`damping for the light source 10. Without such a choke
`36 the filament in an incandescentlight source such as
`light source 10 may physically oscillate under certain
`conditions. Thyristor 14 has an output comprising AC
`pulses having relatively fast rise times. The choke 36
`smooths the shape of these pulses so that there is no
`ringing or spurious oscillation within the light source
`10.
`,
`The input of the microcomputer 16 from the rectifier
`and clamp circuits 30a and 30d is responsive to a series
`of sequential square wave pulses. These pulses are de-
`veloped from the line inputs through either switch 24a
`or 245. For example, if switch 24¢ is depressed the line
`voltage is fed to rectifier and clamp circuit 30¢ which
`provides. half-waverectification and clamps the voltage
`peaks: to a level compatible with the microcomputer
`inputs, that is approximately 5 volts. The switches 24¢
`and 246 are arranged to provide “up” and “down”light
`level changes, respectively. A detailed functional de-
`scription of the consequence of pressing either switch
`will be explained below, but, in general, switch 24a
`increases the brightness level of the light source 10 and
`may therefore be considered an “up” switch and switch
`246 decreases the brightness level of the light source 10
`and may therefore be considered. a “down” switch.
`Accordingly, rectifier and clamp circuit 306 provides
`negative-going square wave pulses as an input to mi-
`crocomputer 16 and the circuit 30¢ provides positive-
`going square wave pulses. The reset network 34 pro-
`vides a signal that resets the microcomputer 16 upon
`initial power upofthe system irrespective offluctuation
`in the DC power supply 18. Such circuits are well
`knownin the electronics art. The zero crossing detector
`20 determines the zero crossing points of the input
`power AC waveform from AC powersource 12. This
`information is synchronized with the crystal oscillator
`32 so that the thyristor 14 may be controlled by gating
`voltage from the AC powersource 12 into the light
`source 10 at predetermined times relative to the zero
`crossing points.
`Microcomputer 16 is a single chip microcontroller
`which may include read only memory and random
`access memory. Such a microcontroller is manufac-
`tured by National Semiconductor Co. and bears the
`model number COP413L. The microcomputer 16 re-
`ceives commandsfrom the rectifier and clamp circuits
`30a and 30d, and synchronizes those commands with
`the zero crossing points of the AC powerline by way of 55
`a signal from zero crossing detector 20, and provides
`appropriate firing commands to thyristor 14 over line
`11. The programs executed by microcomputer 16 and
`the method of operating switches 24a and 240 to
`achieve the programmedresults will be explained be-
`low.
`Referring now to the flow chart diagrams of FIGS.4,
`4(a) and 4(6), there are four possible switch conditions
`for switches 24a and 245. These are identified as the
`decision nodes “up held”, “down held”, “up valid”, and
`“down valid’. There also exists the possibility that none
`of the four above conditions exists and the light will
`remainatits current level by the continuous completing
`
`40
`
`6
`of the zero crossing (“‘Z.C.”’) subroutine, shown in the
`bottom half of FIG. 4, once every 1/120 second. This
`subroutineis responsible for generating a firing or com-
`mandsignal overline 11 which controls the phase angie
`at which the triac fires during each } cycle of the 60
`cycle AC powerinput. If desired, the Z.C. subroutine
`may be executed every other half cycle or every third
`half cycle. Thus an instruction could be provided in the
`program to skip a certain numberofhalf cycles before
`executing the Z.C. subroutine. The effect of such a
`instruction would be to provide a more gradual auto-
`matic fade or preset.
`Thefirst step in the zero crossing subroutine is to
`determineif the current intensity level “C” equals a new
`or desired intensity level. The new level, indicated by
`the letter “N,’’ may have oneofthree values. It may be
`equal to the “preset” level “full on”or “full off.” Thus,
`in a case where N is equal to C, which would be the case
`if none of the switch conditions identified in the four
`decision nodes above currently existed, the microcom-
`puter 16 would determine the time of zero crossing of
`the AC input wave with reference to its own internal
`clock. As soonas it is determined that a zero crossing
`has occurred the microcomputer 16 begins counting
`until it reaches a point in time in the current half-cycle
`of the AC wave at which the voltage input will cause
`the light 10 to have the desired level oflight intensity N
`(FIG.5). This point in time may be expressed as a phase
`angle of the line input wave. At the predetermined
`phase angle the microcomputer will initiate a firing
`signal which will cause the thyristor 14 to gate the
`remaining portion of the AC voltage waveinto the light
`source 10. The resultant voltage input which is shown
`as the “load voltage” line in FIG. 5 is a sharply rising
`pulse whose power content represents a fraction ofthe
`total available AC power line output. The sharplyrising
`input wave form is smoothed by choke 36 to eliminate
`ringing oroscillation of the filamentin the light source
`
`45
`
`50
`
`60
`
`Thethyristor 14 is fired once each half cycle and after
`each firing the microcomputer 16 interrogates the in-
`puts from circuits 30a and 30d to determine the status of
`switches 24a and 246. The interrogation sequence and
`the resulting computations to determine the properlight
`level occur during a brief period of time at the begin-
`ning and at the endof each half cycle of the input wave-
`form as indicated by the shaded portions under the
`curveofthe input wavein FIG. 5. During these periods
`no firing signal is generated and the thyristor 14 remains
`off. These are the points in the cycle, however, when
`the input voltage is lowest and the effect upon power
`availability is therefore negligible.
`The microcomputer 16 determines the status of the
`switches 24a and 24b based upon the numberof sequen-
`tial square wave pulses counted at each of the switch
`inputs from circuits 30a and 306 during each sampling
`period. Depressingeither of the switches 24a or 246 will
`cause circuit 30a or 30b to generate a series of square
`wavepulses for as long as the switch is depressed. Thus,
`the numberof sequential pulses received is a function of
`the length of time that the user manually depresses the
`panel (refer to FIGS.2 and 3)that actuates the switches
`24a and 24d. The microcomputer 16 counts the number
`of pulses in order to discriminate between a “hold”
`condition and a “tap” condition. If the microcomputer
`16 reads a predetermined numberofpulses “n”. whenit
`interrogates a switch input it may interpret the condi-
`tion as a hold, and if it receives a number of pulses
`
`7
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`

`

`4,649,323
`
`_0
`
`8
`7
`sults in a fade in which the incremental increases or
`greater than a predetermined minimum “‘m” but less
`decreases in light intensity are imperceptible and the
`than n it may interpret the switch condition as a “tap.”
`fade appears to be smooth and continuous.
`The predetermined minimum is necessary so that the
`If the up button is tapped while the automatic fade
`micro-computer will not interpret spurious noise as a
`valid switch condition.
`modeis in operation, a different set of conditions will
`exist at the first decision node in FIG. 4(a). In this case
`Referring again to the top of FIG.4, if n pulses are
`C will not be equal to N because N=P=4C and the
`counted while the input from rectifying and clampcir-
`microcomputer 16 will be in the process of fading C
`cuit 30a is being sampled the microcomputer 16 deter-
`towards N. In such a case the microcomputerfirst de-
`mines that the up switch is being held. It then deter-
`termines if N is greater than or less than C. If N is
`mines whether the current level of light C is at full
`greater than C, C is assigned a valuethatis equal to N.
`powerorless than full power. If the current level of
`This causes the level of light intensity to abruptly jump
`light C is less than full the microcomputer increments C
`from C to N. When the zero crossing subroutine is
`and simultaneously makes the new level just achieved
`executed N will then be equal to C and the automatic
`equal to C and the preset level P equal to C. The zero
`fade mode will be circumvented as shown in FIG.4.
`crossing subroutineis then executed. The result of this
`Thus, the difference between a fade and an abrupt tran-
`loop is that as long as the user continues to depress
`sition lies in making C either equal to a new or desired
`switch 244, the microcomputer 16 will cause C to incre-
`level N or in making C equal to some value that is not
`ment onestepat a time per half cycle until the switch is
`N prior to execution of the zero crossing subroutine.
`released.
`If switch 245 remains depressed the mi-
`For example, if N is not greater than C in FIG. 4(a),
`crocomputer 16 will decrement C simultaneously mak-
`microcomputer 16 makes N equal to P, a preset level
`ing N equal to C and P equal to C until the lightis either
`whichis lower than C. Since N is then not equal to C at
`fully off or until the user releases the button controlling
`the commencementof the zero crossing subroutine, C
`switch 24b. The operations N=C and P=C are also
`movesonestep at a time towards N whichis lower than
`memory operations and values of N andPare stored in
`C, and a downward automatic fade is commenced.
`memory for subsequent operations. The above de-
`The operation of the switch when the downbuttonis
`scribed loops represent the preset modeoflight control
`tapped is similar in operation to the situation encoun-
`and serveto establish a new value in memory fora level
`tered when the up button is tapped. If no fade is in
`of light intensity P at the same time that a new level of
`progress when the down button is tapped, C will be
`light intensity is being established in the light source 10
`equal to N. Subsequently, N will be made equal to zero
`through the zero crossing subroutine.
`and the zero crossing subroutine will cause the light
`If during a sampling period the microcomputer 16
`intensity level to fade to off. If a fade is in progress such
`discovers a “tap” condition on the “up” switch 244, it
`that when the down button is tapped, N is either equal
`executes the computational routine shown in FIG. 4(¢).
`to, greater than, or less than C, the light either fades to
`First the microcomputer 16 determines if the current
`off or makes an abrupttransition to off. A delay mode
`level oflight intensity equals the new or desired level of
`may be provided when a downfade is in progress to
`light intensity N. N could be the preset level stored in
`make downward fading more gradual
`than upward
`memory or could be a level correspondingto full power
`fading. Thus,if during a Z.C. subroutine a downward
`on. If C=N, the microcomputer 16 then determines
`fade is detected, the microcomputer 16 delays the thy-
`whether C=full power. If yes, the zero crossing sub-
`ristor firing until the delay subroutine has been com-
`. routine is executed. If no, microcomputer 16 determines
`pleted, incrementing the delay.function one step at a
`_ if N is then equal to P. If yes, the microcomputer makes
`time until its completion. If the down button is pressed
`_N equal to full power and executes the zero crossing
`while an up fadeis in progress, N is made equal to zero
`subroutine. If no, the microcomputer 16 makes N equal
`and C fades toward N in the zero crossing subroutine.If
`to P and executes the zero crossing subroutine. When
`the down is pushed while the system is fading towards
`N=P or N=full and the zero crossing subroutine is
`off, N will be less than C and microcomputer 16 will
`executed, N will not be equal to C and therefore the
`make C equal to N which will cause the auto-fade mode
`command “move C one towards N”in the zero crossing
`in the zero crossing subroutine to be circumvented and
`subroutine will be executed. Since the computational
`the light will make an abrupttransition to off.
`routine in FIG. 4(@) established N as a value which was
`Physically the system represented in the block dia-
`not equal to the current value C of the light intensity
`gram of FIG.1 may beenclosed in a wall mountedlight
`level, the zero crossing subroutine will repeatitself until
`switch. One example of such a switch is shown in the
`N=C (assuming no switches have been depressed in the
`side view of the switch in FIG.2. The switch of FIG. 2
`meantime), at which timethelevel oflight intensity will
`remain constant at the new level N. Thus, when N does
`includes a cover plate 38 and a rectangular bezel 40.
`The bezel 40 encloses a rocker mounted panel 42 which
`not equal C in the zero crossing subroutine, an auto-
`matic fade modeis initiated which moves C one incre-
`includes two inwardly extending fingers 44a and 448.
`The fingers 44a and 446 are adapted to make contact
`mental value towards N each timethe loop is repeated.
`with non-latching push buttons 46¢ and 46). The push
`This loop is executed a chosen numberof times a second
`buttons 46a and 46b are mounted on a PC board 48
`and by choosing that number or the magnitude of the
`which also includes the circuit elements shown in the
`incremental steps through which N moves,the designer
`block diagram of FIG. 1 with the exception of the in-
`may regulate the slope of the automatic fade mode. For
`candescentlight source 10 and the AC powersupply 12.
`example, if the increments of N are made very small it
`The PC board 48 is mounted to an aluminum heat sink
`would take the completion of more loops to move C to
`50. An air gap safety switch 52 is also mounted to the
`the value of N (a slowerfade) than it wouldif the incre-
`heat sink which breaks the circuit when slider 67 is
`mental values of C were made larger (a faster fade).
`actuated. The switch componentsare enclosed in a box
`According to the preferred embodiment, each half
`54 of a size compatible with the current size standards
`cycle is divided into 160 incremental steps and the Z.C.
`for wall-mounted light switch boxes. Inside the box 54
`subroutine is executed every third half cycle. This re-
`
`40
`
`30
`
`35
`
`45
`
`60
`
`65
`
`8
`
`

`

`9
`is choke coil 36. An aperture 56 in box 54 provides a
`means for connection to the incandescentlight source
`10 by way of wire 58. The rocker panel 42 includes
`apertures 60 (only one such aperture is shownin FIG.2)
`in which are mounted light-emitting diodes (LEDs)
`such as LED 62. LED 62is part of LED display 26
`identified in FIG. 1. There may be as many LEDs as
`desired. According to the preferred embodiment there
`should be eight because the National Semiconductor
`chip used for microcomputer 16 has eight outputs
`which may be arranged to provide a signal indicating
`the current level of light intensity. For example, the
`LEDsmaybe arranged in an array extending along the
`rocker panel 42 from top to bottom so that the vertical
`position in the array of the LEDthatis on indicates the
`level of brightness. The nonlatching push buttons 46a
`and 46 correspond functionally to switches 24a and
`245 in FIG. 1. Thus, depressing the upper portion of the
`rocker panel 42 will cause finger 44¢ to engage push
`button 46a¢ and close the “up” switch 24a. Similarly,
`pressing the lower half of rocker panel 42 will close
`“down” switch 246. The rocker panel 42 is biased by a
`pair of angled legs 64a and 646 thatfit snugly within an
`aperturein heat sink 50. The legs 64a and 644 cause the
`fingers 44a and 445 to release the push buttons 46a and
`466 when there is no manual pressure on either half on
`the rocker panel 42.
`Analternative embodiment of the wall mounting for
`FIG.2 is shown in FIGS. 3 and 3a. The wall mounting
`of FIG. 3 includes a cover plate 66 and a two push
`plates 68a and 68b. LEDs 62 are arranged vertically
`from top to bottom throug