Delayed response touch switch controller

The present invention provides a very low actuation force touch control switch for use in brightness control of illumination devices. The control switch comprises a flexible membrane having a plurality of conductors disposed on one surface and secured to a rigid support surface. The conductors are interwoven in a present pattern with portions of the conductors being exposed. A conductive surface is formed in an area under the exposed conductors. The membrane is fastened to the rigid support surface so that a very small spacing is maintained between the exposed conductors and the fixed conductive surface, allowing a very light touch to cause one or more exposed conductors to be shorted to the conductive surface. A microprocessor periodically polls the leads of the membrane to determine which are shorted together and causes an output power level to be adjusted accordingly. The touch control system employs a Delayed-Off feature in which the microprocessor causes a discernible dimming to occur when a DELAYED-OFF selection are on the memberane is pressed but which delays the turning off of the illumination device until a preselected amount of time has passed, thereby allowing a switch operator to leave an area before becoming dark. In addition, Soft-On and Soft-Off processing is employed so that on and off transitions are more gradual and aesthetically pleasing and to provide a period in which to select an alternate brightness level.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to electrical switches and controllers and 
more particularly to a touch actuated switching system that provides 
delayed response timing for termination of electrical power to a 
controlled device. The invention further relates to a touch control system 
allowing selection between a plurality of alternate ON states, an OFF 
state, and a delayed OFF state for an illumination device. 
2. Background of the Art 
Touch control switching systems, especially for controlling illumination 
devices, have proven appealing due to their added convenience and 
aesthetics. However, incorporation of multiple power level dimming schemes 
in such systems or switches has typically required use of complex touch or 
contact sequences which have proven annoying or to difficult to remember 
and use for noncommercial applications. 
To decrease the operational complexity by decreasing the number of discrete 
contact elements that must be separately touched during operation, a class 
of switches based on membrane contacts were developed. In membrane 
switching a series of switch contact is are manufactured on the surfaces 
of one or more adjacent membranes which are deformed into contact by 
touch. This allows a series of contact elements or patterns to be built 
into a relatively compact structure which is operated by touching an 
exterior surface which generally hides the underlying contact structure. A 
variety of otherwise complex power or lighting level control schemes are 
accommodated through a specific, and complex, interconnection of contacts 
without requiring knowledge by the switching system user. The user only 
needs to follow a simple contact pattern on an exterior surface which is 
interpreted by the more complex underlying pattern of switch contacts. 
However, present membrane switching techniques have a number of drawbacks 
which seriously limit their suitability for many applications. One 
drawback is a requirement for relatively high actuation forces which 
reduces their aesthetic appeal and their utility for users having limited 
hand or finger mobility or strength. A second drawback is the generally 
complex multi-layered construction techniques for present membrane 
switches which adds to their cost and complexity. 
At the same time, an inadequacy of all prior techniques for switching 
lights is that switching systems automatically turn lights completely off 
before a system user can leave the room or building. Thus, the user must 
fumble in the dark to leave the previously illuminated area or leave a 
light on. 
What is needed is a method and apparatus for proving touch actuated control 
over the brightness or light output of lamps or similar illumination 
devices that is easy to use and provides a more convenient output scenario 
when adjusting to an off state. 
SUMMARY OF THE INVENTION 
One purpose of the present invention is to provide a touch sensitive 
controller that allows a delayed off response. 
Another purpose of the present invention is to provide a touch control 
switching system that allows ready adjustment or reinstatement of 
illumination levels after a an off command. 
An advantage of the present invention is the provision for a period of 
partial illumination after receiving an off command to allow safe exit 
from a lighted area. 
Another advantage of the prevent invention is the provision of easy 
reactivation of the illumination pattern after requesting an off state. 
The present invention provides a touch control system which is actuable by 
a very light touch while allowing a large number of switching gradations 
or control sequences. 
These and other purposes, advantages, and objects of the present invention 
are realized if a touch control system comprising a pad with multiple 
interleaved conductors disposed on a semi-flexible material which is 
generally mounted on a very rigid base or support structure. The 
semi-flexible membrane is attached directly to the rigid base with a thin 
layer of adhesive which serves as a spacer, leaving portions of the 
interleaved conductors exposed. The rigid base has a recessed portion in 
which a conductive element is mounted and positioned so that it is 
directly beneath exposed portions of the conductors printed on the 
semi-flexible membrane. Because of the extremely small spacing between the 
membrane and the rigid base and because of the rigidity of the base, a 
very light touch causes exposed conductors to come in contact with the 
conductive element, shorting them together. Because of the extremely small 
spacing provided by this construction technique, an extremely light touch 
is required to actuate the switch rendering it far more aesthetically 
pleasing and more suitable for use in many applications. 
In one embodiment of the invention, a precision recess is molded into a 
rigid plastic base, which precisely accommodates the thickness of a 
hot-stamped or printed-on conductor. The interleaved conductors are 
mounted above this conductor and constantly polled or monitored by a 
microprocessor to determine which are shorted together. The microprocessor 
provides a control signal to a triac which alters an controlled output 
power level according to which conductors are shorted together. Using 
lithographic techniques to form the conductors, a complex pattern of 
interleaving can be achieved and a large number of gradations created and 
nearly continuous power control may be provided. 
A Delayed-Off feature is implemented by interleaving at least two of the 
conductors in a DELAYED-OFF selection area on the flexible membrane and 
using conduction between these conductors to initiate a delayed response 
turn off operation. When the Delayed-Off mode is initiated by touch 
contact, the power output level is immediately decreased, dimming any 
controlled light, to indicate to the user that the Delayed-Off has taken 
effect. The microprocessor holds this power level and counts a fixed 
period of time before turning off the lamp. Thus, a person has time to 
leave the room before the room goes dark. 
In addition, the microprocessor utilizes a short period decreasing power 
level ramp to turn off illumination devices connected to the controller.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
The present invention provides a touch control switch or power controller 
that provides several adjustable levels of output power to a controlled 
device such as a lamp or other source of illumination and allows a time 
delayed response to OFF commands. In addition, during execution of OFF 
commands the illumination device is ramped to a zero power level over a 
short period rather than abruptly turned off. These steps are accomplished 
if a touch control switch assembly employing a low activation force switch 
with a series of patterned conductors positioned above a conductive 
surface. The conductors are connected to a control circuit for monitoring 
conduction between the conductors and providing an output control signal 
to an output power device in response to conduction patterns or sequences. 
A schematic diagram depicting control circuitry constructed and operating 
according to the principles of the present invention is illustrated in 
FIG. 1. In FIG. 1, a controller is shown having an interface plug 1 
connected between a lamp 2, or other illumination device, and a source of 
electricity 5 such as a typical wall or floor outlet (not shown). 
A typical application for the present invention is for controlling the 
brightness of household lamps and lighting fixtures operating at 110 volts 
AC. Therefore, the electrical source 5 is described as providing 110 volt 
AC current at approximately 60 Hertz which is standard household voltage 
and frequency in the United States. However, the method of the invention 
is also applicable to other voltage levels up to 220 volts and operating 
frequencies such as 50 Hertz with adjustments to components as would be 
obvious to those skilled in the art. 
The interface plug 1 is configured to act as a receptacle for a matching 
electrical plug (not shown) for the lamp 2. The interface plug 1 is 
generally polarized with one contact blade oriented to connect to a 
neutral or grounded side of the electrical source 5 and a second blade 
connected to a hot side. Electricity from the neutral or grounded side is 
connected directly to both a first input of the controlled lamp 2 and a 
control circuit or controller 4. The second or hot side of the electrical 
source 5 output is connected to a second input of the control circuit 4 
which is in turn connected to a second electrical input of the controlled 
lamp 2. 
As shown in FIG. 1, the control circuit 4 uses a triac 6 interposed between 
the second electrical source connection and the controlled lamp 2. A 
microprocessor 20 is used in the control circuit 4 to determine the 
various operating levels for the lamp 2 and provide control signals to the 
triac 6. 
An exemplary microprocessor 20 useful in constructing the present invention 
is a microprocessor manufactured by the Motorola Company under the 
designation of model numbers 6804, HC 6804 or 68HC6804. This processor has 
the advantage that it is a low power CMOS type device which is organized 
as an eight-bit central processor with an internal instruction set that 
efficiently handles the required control functions or instructions of the 
present invention. 
Of course, the exact microprocessor used and the operating frequency and 
port configurations may be altered so long as required operating 
programming is provided. The exemplary HC6804 microprocessor employs a 
series of internal storage registers, an accumulator, an internal timer, 
ROM type memory, and 32-128 bytes of RAM which are available in other 
microprocessors. However, the present invention only requires a few 
hundred bytes of ROM to implement along with 4-8 internal registers, a 
timer, an accumulator and associated support elements, allowing less 
complex microprocessors to be employed. In the alternative, an Application 
Specific Integrated Circuit (ASIC) is constructed which incorporates only 
the specific amount of ROM, RAM, and other elements, including discrete 
components like timing capacitor 26 (see below). The manufacture of an 
ASIC reduces cost through reduced complexity and may require less power to 
operate. 
The microprocessor 20 operates in five volt electrical power which is 
typically derived from the 110 volt input through a diode 8, resistor 10, 
zener, diode 12 and capacitor 14. The diode 8 supplies semi-rectified 
current which is limited by a the resistor 10 which has a resistance of 
approximately 10 kilo-ohms. A zener diode 12, with a zener breakdown 
voltage of approximately 5 volts, is connected between the output of the 
resistor 10 and ground and clamps the voltage between a power supply point 
16 and ground point 18 to 5 volts. 
The capacitor 14 has a capacitance of approximately 200 microfarads which 
acts to smooth out the semi-sinusoidal signal provided through the diode 8 
which provides a fairly high quality or well regulated positive 5 volt 
supply voltage to power supply node 16. Because the ground 18 is connected 
to the other side of at 110 volt power supply voltage, power supply node 
16 floats at 5 volts above the nominal 110 volts AC power from the 
electrical source 5. 
In the preferred embodiment, power supply voltage is also provided to 
microprocessor 20 through a resistor 22 to all four input terminals of 
port C (labeled PC0-PC3) of the exemplary microprocessor 20. The 
resistance of the resistor 22 is approximately 1 meghms, which limits the 
current to a value which will not damage microprocessor 20. Integrated 
circuits generally contain voltage protection diodes which clamp input 
voltages above Vcc to Vcc+1.6 volts on the internal circuitry of the 
integrated circuit and similarly with voltages below 0 volts the voltage 
supplied to the integrated circuit is clamped to Vss -1.6 volts. Because 
of the input protection devices, what microprocessor 20 actually sees is a 
square wave input going from nominally 0 to 5 volts. 
Microprocessor 20 controls the operation of triac 6 through capacitor 24. 
During periods when triac 6 is off, output terminals P80 through P85 are 
maintained at a high, 1, logic level, i.e., 5 volts. When microprocessor 
20 is to turn on triac 6, output terminals P80 through P85 go to a low, 0, 
logic level, i.e. 0 volts. The charge stored on the capacitor 24 is 
discharged into a P-type injection port of triac 6 which causes triac 6 to 
turn on. Output ports PB0 through PB5 then return to the high or 5 volt 
level and the capacitor 24 is recharged by internal leakage through the 
triac 6. 
The capacitor 26 adjusts or sets the operating frequency of microprocessor 
20. The microprocessor 20 has an internal clock generation circuit whose 
operating frequency is adjusted by an external capacitor. 
A capacitor 28 is connected to the reset input terminal to prevent stray 
fields from generating a reset signal in the microprocessor 20. 
Microprocessor terminals PB6, PB7 and through are connected to a 
series of dim, low, L1 through 6, mid and high leads of a touch switch 30. 
A layout of a membrane portion of the touch switch 30 is shown in FIG. 2. 
As shown in FIG. 2, the dim, low, mid and high leads of the switch 30 
cross a power level control area 40 covering 4 sections of dimmer area 40. 
Leads L1 through L6 interweave through the dim, low, mid, and high leads 
in a serpentine fashion. The dim lead is interwoven with the high lead in 
an OFF selection area 38 and the low and high leads are interwoven in a 
DELAYED-OFF selection area 36. A printed insulator 34 covers all leads 
excepting in areas 36, 38 and 40. In these areas the leads are exposed. 
FIG. 3 is a sectional view of membrane 30 showing the exposed low, dim and 
high leads. These leads are supported by substrate 31 but are not covered 
by insulation 34 in this selection area. FIG. 4 is a section of membrane 
30 taken along line 4--4 of FIG. 2. FIG. 4 shows how leads L1 through L4 
and the high lead are insulated by insulation 34 but lead HIGH is exposed 
in opening 40. FIG. 5 is a rear view of membrane 30 through substrate 31. 
FIG. 6 is a top view of base 42. Recess 44 is a flat recess approximately 2 
mils below the flat surface of base 42. Conductor area 46 is formed in 
recess 44. In a preferred embodiment conductor 46 is formed by carbonized 
paint. Conductors 50 and 52 are formed in a simi)ar manner. Ventilation 
hole 48 is included to avoid alteration of the tolerances between membrane 
30 (FIG. 2) and base 42 due to variations in ambient temperature and/or 
barometric pressure changes when membrane 30 is adhesively placed on the 
surface of base 42. 
FIG. 7 is a side view of base 42 and conductor 46. 
FIG. 8 is a side view showing membrane 30 attached to base 42 by adhesive 
43. Because of the extreme rigidity of base 42, which is preferably formed 
with high rigidity plastic, this spacing tolerance between the exposed 
leads of membrane 30 and conductor regions 46, 50 and 52 can be very small 
on the order of 50 microns or less. Because of this small tolerance, a 
very light touch approximately one half ounce, is required to cause 
connection between the leads formed on membrane 30 and conductor regions 
46, 50 and 52. Because of this tight tolerance, membrane 30 must be formed 
of a plastic such as mylar which is resistant to moisture and temperature 
alterations of size and shape and membrane 30 must be fastened to the 
surface of base 42 using an adhesive 43 such as the 467 adhesive by 3M 
Corporation which is also moisture and temperature stable. 
In the described embodiment, adhesive 43 acts as a spacer between membrane 
30 and base 42 to provide precise spacing between membrane 30 and 
conductor regions 46, 50 and 52. Alternatively, adhesive 43 is made 
thicker, approximately 7 mils, and recess 44 is eliminated. In this 
alternative embodiment, the adhesive itself provides all the required 
spacing between the conductors of membrane 30 and conductor regions 46, 50 
and 52. 
To activate the touch control switch of the present invention and select an 
illumination setting, manual pressure is applied on the top of the 
membrane 30. When pressure is directed on the membrane 30 above conductor 
region 46, as shown in FIG. 9, one or more of the leads L1 through L6 will 
be shorted to one of more of dim, low, mid and high leads through 
conductor 46. Microprocessor 20 is programmed so that a logical 0 is 
placed on each of the dim, low, mid and high leads, successively and leads 
L1 through L6 are normally at a logical 1. Microprocessor 20 then polls 
terminals through to determine if conductivity is present between 
the selected dim, low, mid and high lead and one of the leads L1 through 
L6. If continuity is found, that fact is stored in a register within 
microprocessor 20 and is used as timing data for triggering the triac 6. 
The controller 4 and, thus, the microprocessor 20 are powered on as long as 
the interface plug 1 is connected to an electrical source 5. To preserve 
aesthetics no separate ON switch is used, although possible. This means 
that the controller 4 is always ready to receive new commands or 
brightness level requests from the switch membrane 30, subject to polling 
timing described below. 
The operation of the microprocessor 20 and associated support elements and 
leads low through high are better understood from viewing the flow diagram 
of FIG. 10 in conjunction with the circuit of FIG. 1. 
The microprocessor 20 is initialized or initializes the controller 4 on 
initial power up so that the microprocessor port A leads -, port B 
leads PB6-PB7 and port C leads PC0-PC3 are set or configured as inputs; 
and port A leads -, and port B leads PB0-PB5 are set as outputs, 
except for polling commands as used below. The voltage on the PC0-PC3 
leads, from register 22, are defined as high and the PB1-PB5 and - 
leads set at a high or 1 logic level. A system status register is loaded 
with a multi-bit command which contains bits defining system status for 
certain basic operating parameters. These parameters are lamp ON or OFF, 
Soft-On feature active or inactive, polarity for the triac 6 (low 
positive, high negative), Delayed-Off active or inactive, and Soft-Off 
inactive or active. Initially these values are set as OFF, inactive, low, 
inactive, and inactive. 
Additional registers, such as a register BLevel are set for establishing an 
initial Brightness Level. The BLevel register is initially loaded with a 
value on the order of 5.6 milliseconds of delay. The BLevel register value 
is also loaded into a Timer Counter Register TCR. 
As the line voltage connected to plug 1 passes through one half cycle of 
the sinusoidal alternating current provided by the electrical source, 
microprocessor 20 (FIG. 1) detects zero voltage cross over transitions 
through input terminals PC0 through PC3. These cross over points are used 
as markers or flags to prompt a processing cycle for the microprocessor 20 
operating instructions or program. 
The operating frequency of microprocessor 20 is approximately 125 kilohertz 
which is approximately 2000 times the operating frequency of standard 
household current. The exemplary HC 6804 microprocessor requires on 
average four clock cycles to perform a given command or instruction. 
Therefore, the microprocessor 20 executes approximately 500 instructions 
for every cycle of the power source 5 and approximately 250 instructions 
every one-half cycle. The one-half cycle period representing the time 
between zero voltage cross over points for the sinusoidal AC current 
source. As before, the value of capacitor 26 can be altered to establish 
an alternate timing cycle for the microprocessor 20 where other electrical 
sources are used. 
During a given half-cycle, the longer triac 6 remains off, the lower the 
average power received by lamp 2 and the dimmer the lamp 2 will be. 
Conversely, the longer the lamp 2 is turned on the brighter it will be. 
Thus, when the microprocessor 20 is set to provide a particular brightness 
setting, microprocessor 20 adjusts the amount of delay time that passes 
into each half-cycle before the triac 6 is turned on. The lowest intensity 
or brightness setting typically translates to about 6.7 milliseconds of 
delay before allowing triac 6 to turn on and at the brightest setting, 
microprocessor 20 allows triac 6 to turn on about 1.6 milliseconds after 
the start of a half cycle. This 1.6 millisecond delay is used to allow 
microprocessor 20 to poll the required leads of membrane 30 to determine 
if a new setting or brightness has been selected and perform necessary 
program steps. 
At the start of each half cycle or 1.6 millisecond delay period, the 
microprocessor 20 begins operation by pulling or strobing the lead low 
to poll the various input leads and determine their conductivity with 
7. The microprocessor 20 also starts an internal timer which is used to 
set the firing time for the triac 6. 
With the lead pulled low, the touch pad is checked for brightness 
commands by checking one level of each of the leads -P5 one at a time. 
If any of the leads are in a low state then a time delay value associated 
with that lead is loaded into the BLevel register. For the preferred 
embodiment, the levels associated with conductivity between lead and 
the -A5 leads is on the order of 2.0, 3.0, 3.2, 3.4, 3.5, and 3.6 
milliseconds respectively. The microprocessor 20 then sets the lead 
high and the lead is strobed low. The - leads are again checked, 
this time in descending order, and another series of associated values 
loaded into the BLevel register. These values are 3.7, 3.8, 3.9, 4.0, 4.1, 
and 4.2 milliseconds respectively. Note that the lowest or smallest delay 
values are checked first so that the brightest setting specified by 
touching the touch pad is selected first to the exclusion of other or 
contradictory commands during a given polling cycle. Once a brightness 
level is selected and loaded into the BLevel register a new brightness 
level cannot be selected until the next cross over point. 
The above procedure is used with leads PB6 and PB7 by setting them as 
outputs and strobing them to a low value and checking the leads - 
and then - respectively. The values loaded into the BLevel register 
when these leads are detected as low are 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 
4.8, 4.9, 5.0, 5.1, 5.2, and 5.3 milliseconds respectively. 
The microprocessor 20 then changes or sets the PB6-PB7 leads to inputs with 
the lead then strobed low. The leads PB7 and PB6 are checked to 
determine if contact has been made in the OFF selection area 36 or 
DELAYED-OFF selection area 38. 
Of the 26 combinations between the dim, low, mid, and high leads, and the 
leads L1 through L6 on the membrane 30, twenty-four are used to define 
gradations or levels of brightness for the lamp 2 and two are used to 
define "OFF" and "DELAY-OFF" states or commands. The differences in 
brightness between adjacent levels are very difficult to perceive by the 
human eye, thus the variations in levels appear to be a continuous scale. 
Because of the light touch and the continuous scale appearance of the 
control switching system, the described embodiment provides a lamp dimming 
system with the tactile qualities of touch lamp control and the aesthetic 
qualities of continuous dimming. 
The microprocessor 20 continues to monitor or poll the leads - on a 
periodic basis and detects any new commands or requests for altered 
brightness. If a new level command is detected then a value for the 
corresponding delay from zero point cross over is transferred into the 
BLevel register which is used to determine the timing for firing the triac 
6. 
While the variations in brightness as implemented by the present invention 
advance the art, additional features are provided by the method and 
apparatus of the invention which prove most useful. 
One such feature is the implementation of a Soft-Start technique for 
initially turning on the lamp 2 after being turned off. In the Soft-Start 
or Sott-On mode of operation the microprocessor 20 retrieves the current 
brightness level from the BLevel register and saves it in a temporary 
Command Level (ComLevel) storage register. The ComLevel value, from the 
BLevel register, is used as a target brightness level unless the touch 
control user sets a new level. The target level is adjusted if a different 
one is requested by a control user before the ComLevel value is reached. 
Typically the BLevel value is then set at a very low level, say on the 
order of 5.6 milliseconds of delay as set initially in the BLevel 
register. This means that the initial average power delivered to the lamp 
2 is very low which results in a dim light level. The BLevel value or 
number is then decreased by subtracting 32 microseconds from the BLevel 
register value and reloading the new value into the BLevel register on 
each microprocessor 20 instruction cycle. At the beginning of each 
microprocessor instruction cycle the new BLevel value is compared to the 
value stored in ComLevel to see if the target level has been reached. If 
it has, Soft-On processing is completed. Otherwise, the Soft-On processing 
continues until completed, and does so to the exclusion of other level 
changes or commands. Once the microprocessor 20 has adjusted the triac 6 
to achieve the desired brightness level, the appropriate bit in the system 
status register is set low to indicate that the Soft-on processing routine 
is to be ignored in subsequent operational checks and program steps until 
the light is turned off. Another useful feature of the present invention 
is the implementation of the converse procedure called Soft-Off or 
Slow-Off which is used for added safety and aesthetics. When a touch 
control user wishes to turn the lamp off immediately, the portion of 
membrane 30 labeled area 38 in FIG. 2 may be pressed. During the 1.6 
millisecond polling cycle of the microprocessor 20, conductivity between 
the dim and high leads is checked. If microprocessor 20 detects 
conductivity between these two leads the current value of the BLevel 
register is stored in an Entry Level (ELevel) register. The value in the 
ELevel register is used as the new BLevel and a flag or bit set in the 
status register to indicate that Soft-Off is active (and Delayed-Off is 
inactive, see below). 
On each successive microprocessor instruction cycle, 32 microseconds is 
added to the delay value in the BLevel register and stored in the BLevel 
register until a targeted low value is reached. The low value is prestored 
in ROM and can be as low as the lowest value or 5.6 milliseconds, or any 
other suitably low value. It will take on the order of 250 half-cycle 
periods of the electrical source 5 to reach the lowest brightness value 
from the highest value. This is approximately 4 seconds. The time to reach 
a minimum brightness level from other brightness levels is, of course, 
shorter. 
This Soft-Off feature allows time to hit another setting where the OFF 
selection portion of the membrane 30 was touched in error. This is 
especially useful for the present invention since a very light touch is 
all that is required to activate the switching control of the present 
invention unlike previous designs. If desired a double touch of the OFF 
selection portion of the membrane can be used to accelerate the OFF ramp 
by providing continued polling and additional changes in the values stored 
in the BLevel register. 
Another feature of the present invention is activated by pressing the 
DELAYED-OFF selection area 38 of the membrane 30 so that the 
microprocessor 20 detects conductivity between the low and high leads and 
enters a Delayed-Off program. If Delayed-Off is selected by shorting the 
leads and PB6 together a flag bit is set in the status register to set 
Delayed-Off active, and the Soft-Off bit is also set inactive. Delay timer 
or control bits are set low and the current brightness setting or level is 
loaded from the BLevel register into an Entry Level (ELevel) register and 
sets a value in the Delay register (DLevel). The ELevel value is used as 
the starting point for the delayed-off operation. 
The microprocessor 20 automatically adjusts the brightness level to dim the 
lamp 2 in response to the Delayed-Off request as a confirmation of the 
command. The exact drop in brightness level depends upon the current 
brightness. If BLevel is the highest brightness setting then the this 
level is decreased by two levels, i.e. down to 5.3 milliseconds. 
Otherwise, this level is decreased a smaller amount which varies according 
to how far down the brightness level BLevel is. That is, a smaller 
incremental change in timing is required to have a noticeable impact on 
the light brightness at lower levels so a smaller decremental value is 
used. 
A preselected value for decreasing brightness at lower levels is programmed 
in the read only memory of microprocessor 20 and is selected so that 
perceptible dimming is provided no matter what the brightness setting of 
lamp 2 may be. 
The new brightness level is stored in BLevel and in an Entry Level 
register. The microprocessor 20 checks to see if BLevel changes due to a 
user input, as where the user seeing the light dim, realizes that 
DELAYED-OFF was touched in error or has a change of mind. If BLevel has 
changed, then the Delayed-Off processing is discontinued. If there is no 
level change or command, the microprocessor 20 retrieves a countdown value 
from the DLevel register, adds one and stores the new value in the DLevel 
register. The value in the DLevel register is compared to a fixed time 
interval to see if enough time has elapsed to turn off the lamp 2. The 
value chosen for the fixed delay period is about 30 seconds. This is 
approximately equivalent to 3600 counts in the delay register based on the 
120 Hertz operating clock rate discussed above. 
The Delayed-Off state allows a present amount of time for a lamp user to 
either leave the area (room, building) or initiate a new brightness level. 
The amount of time is determined by a value stored in ROM and is typically 
set to approximately 30 seconds. This value is somewhat arbitrary and is 
established according to average need. However, this value can also be 
determined by an R-C timing constant or similar voltage level which is 
monitored by the microprocessor 20. Therefore, a small variable resistance 
device could be connected to a lead of the microprocessor 20 and adjusted 
to alter the time delay where desired. 
Once the delay register value reaches the targeted value the microprocessor 
20 proceeds with the Soft-Off feature. In this mode the microprocessor 20 
changes the level setting every few cycles until the level is reduced to 
zero. In the alternative, the microprocessor 20 can also detect a 
secondary request by touching the area 36 which is interpreted to mean the 
lamp should go OFF completely and immediately thus overriding soft off and 
time delay off. 
Although specific embodiments are herein described, the use of specific 
embodiments is not to be construed as limiting the scope of the invention. 
The scope of the invention is limited only by the claims appended hereto.