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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to an electrical switch for controlling lights or
other appliances, of the type which can exercise control in a
preprogrammed manner to turn controlled equipment on and off automatically
in a manner simulating normal manual usage of a switch controlling the
device.
2. Review of the Art
Switches with such a capability are widely utilized, both for security
purposes in order to turn lights on and off in a manner such as to provide
an appearance that premises in which the switch is installed are occupied,
or to turn lights or appliances on for preprogrammed periods each day.
Typically such switches incorporate a programmable timer of either
electromechanical or electronic construction, and means for a user to set
up manually a desired switching program. With the development of
electronic technology, it has become economically viable to provide quite
sophisticated programming capabilities in such devices, but in common with
most programmable domestic appliances, programming requires a degree of
mental application and assistance from instructions which results in the
average user not fully exploiting the programming capabilities of the
equipment, and rarely reprogramming it once an acceptable program has been
achieved, either because of the effort involved, or because the
programming instructions are no longer to hand.
Such switches may either take the form of a programmable switching device
connected between an outlet and a light or appliance to be controlled, or
may replace a conventional switch.
Examples of known programmable light switch controllers may be found in
U.S. Pat. Nos. 4,521,843 (Pezzolo), 4,570,216 (Chan) and 4,354,120
(Schornack). The Chan and Schornack patents disclose the concept of a
programming mode in which operations of the switch in a 24 hour period
following initialization of the switch are memorized and repeated
indefinitely. The program can apparently only be altered by resetting the
device, or by powering down, i.e. disconnecting and then reconnecting the
switch from the circuit in which it is used, followed by complete
reprogramming. In practice, this means, that the device cannot be
reprogrammed in this mode without first destroying the existing program
and then waiting for twenty-four hours.
SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a switch which can
be readily programmed and reprogrammed to provide many of the functions of
prior art switches without requiring any mental effort or reference to
instructions by a user, which can be implemented with no external control
devices apart from the switch activator itself, and which can have the
general appearance of a conventional switch or outlet adaptor without
needing any dials or displays.
Accordingly the invention provides a programmable switching unit for
controlling electrically powered devices, comprising:
a microcontroller;
means associated with the microcontroller for sensing on and off conditions
of a controlled device;
manually operated control switch means;
means associated with the microcontroller for sensing alternative
conditions of the control switch means; and
electrical switching means in series with the controlled device and
controlled by the microcontroller;
the microcontroller operating in accordance with a first control program
routine when it senses a first condition set by said control switch means,
and a second control program routine when it senses other conditions set
by said control switch means, said second control program routine causing
the microcontroller to continuously update an accumulation of memorized
time of on and off transitions of said controlled device, and said first
control program routine causing the microcontroller to control said
electrical switching means at times derived from said accumulated
memorized times of on and off transitions of said controlled device.
The switching unit may include a momentary contact switch, momentary
closures of which are sensed to toggle the condition of the controlled
device and control said first program routine, and a prolonged closure of
which is sensed to cause the microcontroller to enter the second routine,
or the switch may be built into a single or multi-adaptor adaptor and use
a current sensing transformer to sense the condition of the device, with a
separate switch to initiate the second routine.
SHORT DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a front view of a first embodiment of a programmable switch;
FIG. 2 is a side elevation of the switch;
FIG. 3 is a schematic diagram of an internal circuit contained in the
switch;
FIG. 4 is a schematic diagram of a second preferred embodiment suitable for
incorporation into a conventional multiadaptor unit;
FIG. 5 is a front view of a third and presently preferred embodiment of a
programmable switch;
FIG. 6 is a side elevation of the switch of FIG. 5; and
FIG. 7 is a schematic diagram of the switch of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1 and 2, the switch of the invention may be constructed
so as to be an exact physical replacement of a conventional light switch,
even to the extent of accepting conventional switch cover plates. Thus the
switch comprises a support plate 2 by means of which the switch is mounted
in the usual manner in a conventional wall box, a switch tumbler 4, a
housing secured to the rear of the switch plate and accommodating the
switch mechanism as well, in this case, as the electronic circuit to be
described and a compartment holding a battery 6, the battery being
accessible for replacement through an aperture 8 in the support plate 2
after removal of a conventional decorative cover plate (not shown). The
body has conventional terminals 10 for connection to the circuit in which
the switch is placed, typically but not necessarily a lighting circuit.
The switch differs from conventional switches in that as well as
conventional "ON" (tumbler up) and "OFF" (tumbler down) positions, both
shown in broken lines, it also has a stable intermediate or "AUTO"
position.
As best seen in FIG. 3, the switch mechanism denoted in this figure as SW,
provides a single pole double-throw switch in which a grounded common
conductor is connected to a resistor R9 when the switch is in the "ON"
position, and to a resistor R10 when the switch is in the "OFF" position.
When the switch is in the "AUTO" position, no connection is established.
The switch SW does not directly control the circuit in which the switch
assembly of the invention is placed, but instead provides data to the
circuit shown in FIG. 2.
The exemplary circuit shown is built around a Motorola (Trademark)
MC68HC05J1 mask-programmed microcontroller MC. This is a low-power HCMOS
device containing 1024 bytes of user ROM, 64 bytes of RAM, two I/O ports,
(Port A having eight bits PAo to PA7, and Port B having six bits PBo to
PB5), a timer section, two levels of interrupts, and an internal watchdog
function. Further information concerning this microcontroller will be
found in the data book MC68HC05J1 Terminal Data published in 1989 by
Motorola. It will of course be understood that other microcontrollers
having comparable features could be utilized with appropriate amendments
to the circuit.
For purposes of description,, the circuit can be broken into eight
sections: namely, power supply, line-frequency interrupt pulse shaping,
reset, battery, automatic indicator, clock, switch, and output sections.
AC voltage is coupled to the power supply section through coil L1 and
resistor R1. Diodes D1-D4 form a full-wave bridge rectifier, the output of
which is coupled through transistor Q1 and a diode D5 to an electrolytic
capacitor CE1. The base of this transistor is controlled by a silicon
bilateral switch SBS1, which is coupled to the rectifier output through a
resistor R2.
As soon as the voltage appearing across the silicon bilateral switch, and
thus across the base-emitter junction of the transistor Q1, exceeds
approximately 0.65 volts, the transistor Q1 turns on and charges capacitor
C1 to the voltage at the base of the transistor Q1 minus the forward
voltage of the base-emitter junction of the transistor. When the voltage
across the silicon bilateral switch exceeds approximately 8 volts the
device rapidly goes into conduction, causing the voltage at the base of
the transistor Q1 to drop almost to zero. This turns off the transistor
Q1, and the capacitor CE1 does not charge any further for the duration of
the half-cycle. Capacitor C1 is a ceramic capacitor bypassing high
frequency noise to circuit ground.
This raw supply voltage is regulated by a resistor R5 and Zener diode Z2 to
approximately 5.1 volts, to provide a supply VDD for the microcontroller.
The voltage at the emitter of the transistor Q1 is coupled through resistor
R4 to Zener diode Z1 to provide pulse shaping of double line frequency
interrupts applied to an interrupt Din IRQ on the microcontroller MC, thus
providing a 120 Hz interrupt to the microcontroller. The microcontroller
is initialized so that this pin is edge sensitive.
Resistor R8 and capacitor C2 provide a reset pulse to a RESET pin of
microcontroller MC, on the initial application of power to the circuit, to
ensure that the microcontroller is initialized properly.
Steering diodes D6 and D7 and resistor R12 are used to switch and test the
battery power supply to the circuit. When the power supply is operating
normally, the diode D7 is reverse biased since the power supply voltage is
approximately 5 volts, while the battery voltage is approximately 4 volts.
Should the power supply to terminals 10 fail, the diode becomes
forward-biased, and supplies the microcontroller terminal VDD.
Diode D6 and resistor R12 form a battery-test section of the circuit and
work as follows. Microcontroller PORT B bit PB4 is configured as an input
pin, and PORT B bit PB5 is configured as an output pin. When a
battery-test function is selected, the microcontroller sets the logical
state of PORT B bit PB5 (which is normally "1", i.e. 5 volts) to "0", i.e.
ground, which causes current to flow from the battery positive terminal
through diode D6 and resistor R12 to PORT B bit PB5. The current through
resistor R12 is several times that required to run the microcontroller. If
the charge in the battery is low, the loading upon it will cause the
voltage at the positive terminal to be less than the 3.5 volts required
for PORT B bit PB4 to read a "1". If PORT B, bit PB4 does not read a "1",
then the Light Emitting Diode LED 1 is turned on as described in the next
section, but intermittently so as to provide a flashing warning.
The visible light emitting diode LED1 and resistor R11 are used to indicate
that the switch is in the "automatic" mode. When PORT B bits 2 and 3 are
set to "0", current flows from VDD through these two components, turning
on the visible LED, which may be located within the switch tumbler.
Resistor R7 is selected and connected between OSC1 and OSC2 terminals of
microcontroller MC to cause the microcontroller clock to run at
approximately 2 megahertz.
The single-pole, double-throw switch SW is read by the microcontroller to
control operation of the device. The switch couples either R9 or R10, and
therefore PORT B bit PB1 or bit PB0 to circuit ground to indicate
respectively, "ON" or "OFF" conditions of the switch. If neither bit is
pulled to "0", operation is automatic.
All bits in PORT A are configured as output pins, and are connected in
parallel and normally held at "0". When so controlled by the programming
of the microcontroller, all outputs go high and provide a short-duration
"on" pulse to deliver approximately 100 mA to the gate of a Triac TR1.
This large gate current is necessary to ensure clean triggering of the
Triac, which is associated with a filter comprising between resistor R3
and capacitor C3 in parallel, and coil L1 in series with it which provide
a filter to prevent the propagation of radio-frequency interference. In
addition, resistor R3 and capacitor C3 act as a snubbing network to
prevent unwanted triggering of Triac TR1 by line noise exceeding its dv/dt
threshold.
FIG. 4 illustrates the circuit of an alternative embodiment for
incorporation in a conventional single or multi-adaptor through which one
or more appliances can be connected to an outlet. This resembles the
previous embodiment in many respects, and only the differences will be
described.
Externally, the unit will incorporate line and neutral pins 110 for
insertion into an outlet, and line and neutral pin receptacles 112,
duplicated as necessary, for the reception of the pins of appliance plugs.
A ground pin and connected ground receptacle (not shown) may be provided
but do not form part of the invention. The only external difference from a
conventional adaptor is the provision of a single pole on/off switch 114,
which in the ON position corresponds in function to the "AUTO" position of
the switch in the previous embodiment.
This embodiment does not provide a facility for manual switching of a
controlled light or appliance. Instead it senses, when the switch 114 is
off, whether or not a controlled appliance is turned on by sensing the
passage of current to the receptacles 112 by means of a current sensing
transformer TR2, similar to those used for example in ground fault
interrupter devices. The primary of the transformer is in series with the
line receptacle(s) 112, whilst its secondary is connected via a diode D9
and a current limiting resistor B13 to a reservoir capacitor CE2. When
current through the primary reaches a threshold level, the potential
across capacitor CE2 will rise high enough to raise pin PB1 of the
microcontroller to logical "1" level. Development of excessive potential
across capacitor CD2 is prevented by Zener diode Z3.
The bridge rectifier formed by diodes D1 to D4 is supplied from a
transformer TR3 across the line and neutral pins 110, instead of through
resistor R1 as in FIG. 3, thus reducing heat dissipation problems and
permitting use of a simplified power supply circuit in which the series
transistor Q1 and its associated base circuit components are eliminated.
The battery check circuit of the previous embodiment is omitted, since a
rechargeable battery B1 is used. During normal operation, the battery
trickle charges through R12, whilst under power failure or unplugged
conditions, the battery powers the microcontroller MC through diode D6.
Essentially the same software routines, mask programmed into the
microcontroller, may be utilized for both embodiments, since the data
obtained from the switch SW in its "ON" and "OFF" positions, and that
derived from the current sensing transformer are essentially equivalent.
The software consists of three parts: A main program, a timer interrupt
section, and a line frequency interrupt section. Each part will now be
described.
The main program merely serves to disable interrupts, initialize the I/O
ports, and timer, and initialize variables in several RAM locations in the
microcontroller upon the first application of power, and then to enable
interrupts and put the microcontroller into a "WAIT" mode, unless one of
the two interrupts or a RESET occurs. The variables include LOAD ON
indicating whether a circuit is to be completed between terminals 10,
RANDOM indicating the magnitude of a COUNTDOWN variable. A built-in
watchdog timer in the microcontroller is also enabled, which requires to
be reset at predetermined intervals to verify correct functioning of the
software, failing which a RESET occurs.
The timer interrupt routine is executed 65.536 milliseconds under control
of a built-in timer in the microcontroller. It increments a real time
clock register maintained by the controller, and then tests a flag CNTDN.
If the flag is set, it decrements a register COUNTDOWN and tests whether
the register content is zero. If the register content is zero, it resets
the flag CNTDN and changes the condition of a flag LOADON. The watchdog
timer is then reset, and the status of the unit is then read; in the
embodiment of FIGS. 1-3 the switch SW is read by determining the status of
bits PB0 and PB1 of Port B of the microcontroller, whilst in the
embodiment of FIG. 4, the status of the same bits indicates the condition
of switch 14 and whether current is passing in the circuit, i.e. whether a
lamp or appliance being controlled is turned on. According to whether the
condition of these bits indicates that the circuit is on, the circuit is
in "AUTO" mode, or the circuit is off, one of three branches is selected.
In each branch, the status of a flag, respectively WASON, WASAUTO or
WASOFF is tested, and if the flag is set ON, AUTO or OFF routines
respectively are executed. Otherwise, the routine returns after setting
the respective flag so that the status oil the switch can be verified at
the next interrupt.
The line interrupt service routine is executed each time a twice line
frequency pulse is received at the pin IRQ of the microcontroller MC. The
routine tests the flag LOADON, and if it is set, it applies a turnon
pulse, via the lines of Port A, to the control electrode of the triac TR1
so that for the balance of the half cycle the terminals 10 (FIG. 3) or the
line terminals 110 and 112 (FIG. 4) are connected, thus maintaining the
controlled lamp or appliance in an ON condition. Thus the condition of the
flag LOADON determines whether or not the appliance is turned on or off.
The routine then increments a counter RANDOM, test whether a particular
count (in this example 206) has been attained, in which case the counter
is reset, and returns from the interrupt. In the FIG. 4 embodiment, the
routine will also check whether the circuit is in AUTO mode, and if it is
not, the turnon pulse will be transmitted to the triac TR1 so as to permit
manual switching of the device.
The ON routine first checks (in the FIG. 3 embodiment only) whether a
battery test flag is set, and if it performs a battery test routine using
the hardware features already described. It then tests the LOADON flag. If
the flag is not set, it is set, the time is read from the real time clock
register REALTIME, a table of stored ON times is scanned for a match, and
if no match is found, the new ON time, represented by the time read from
REALTIME, is stored in the table. If the LOADON flag is already set, the
time read from REALTIME is checked against the table of stored ON times
and a table of stored OFF times, and if a match is found, the table entry
concerned is cancelled. The resolution of the real time clock can be quite
coarse, providing for example time slots of about 6 minutes (240 time
slots per day).
The OFF routine is similar to the ON routine, except that the LOADON flag
is tested for a reset condition, and the left hand branch accesses the OFF
times table rather than the ON times table.
The AUTO routine first tests the CNTDN flag, and returns if it is reset. If
set, it then tests the LOADON flag. If the LOADON flag is not set, it
fetches the real time from REALTIME, increments it and tests the OFF times
table for a match, returning in the absence of a match or branching to a
countdown routine if there is a match. If the LOADON flag is set, similar
steps are taken with the ON times table. The countdown routine test the
CNTDN flag and exits if it is set. Otherwise it places content of the
RANDOM register in the COUNTDOWN register, sets CNTDN and exits.
The effect of the ON and OFF routines, which are only operative when the
unit is not in the AUTO condition, is to store tables of ON and OFF times
accumulated over the immediately preceding twenty four hour period
(obviously this period can be varied to suit any particular application),
reflecting either the condition of the switch SW (FIG. 3), or whether
current is passing to a controlled lamp or appliance (FIG. 4). When the
unit is in the AUTO condition, the triac will be controlled as to maintain
a controlled lamp or appliance either on or off in accordance with the
table entries. In order to introduce a random element into the control
cycle, the register COUNTDOWN is loaded with a semi-random number taken
from the register RANDOM, which register is counted down as a time slot is
reached that is one in advance of a timeslot entered in one of the ON and
OFF time tables, so that the actual turn-on and turn-off times are
somewhat random.
In use, the device may be utilized as a normal switch or adaptor, under
which circumstances it memorizes a history of ON and OFF events over a
period limited by the length of the real time clock cycle, or placed in an
AUTO mode, in which it replicates the memorized history of ON and OFF
events occurring during the period preceding its being placed in AUTO
mode, with a limited degree of semi-random variation of on and off times.
No special programming procedure is required, nor is any time setting
provision required. If the device has a 24 hour cycle, then events during
the 24 hours preceding entering the AUTO mode will be replicated. If the
cycle time is a week, then events over a week will be replicated.
The embodiments of the invention so far described, whilst representing a
substantial advance of the manual programming of most prior art devices,
and the `inherent` but inflexible programming of the device described in
the Chan patent referred to above, nevertheless depend on the twenty-four
hour (or other) period immediately preceding entry of the automatic mode
of the switch being representative of normal usage. Furthermore, the three
position switch utilized in the first embodiment is a nonstandard and thus
expensive device.
I nave found that, by combining accumulated data relating to times of ON
and OFF transitions of the controlled device from a plurality of preceding
periods (usually 24 hour periods), the likelihood of providing a schedule
for automated operation which is representative of normal usage is greatly
improved. Thus for example by maintaining tables of ON and OFF transitions
for each of three twenty-four periods which are updated sequentially
during normal operation of the switch, and combining the contents of these
tables on a logical OR basis during automatic operation of the switch,
representative usage during any one of the three days prior to entering
automatic operation is likely to provide a satisfactory simulation of
normal usage, particularly when the timings of the ON and OFF transitions
are adjusted by small random amounts as previously discussed. Other modes
of data accumulation are possible. For example a fixed number, for example
eight, of both the most recent ON events and the most recent OFF events
could be stored, in order to provide a schedule of events for use in the
automatic mode over a twenty-four hour period.
Referring to FIGS. 5-7, the electronic circuit of FIG. 7 is contained
within a housing 201 of a momentary contact switch 200 having a mounting
plate 202 and a push plate 20, which acts to close the switch when
pressed. An light emitting diode (LED) 201 is mounted in the push plate.
The circuit itself is based upon the ST6210 microcontroller from
SGS-Thompson which is specifically designed for use in power control
applications. This microcontroller incorporates clamping diodes designed
to provide a high degree of transient protection, enabling their direct
connection to the supply through suitable resistor chains. The circuit is
connected between line and load terminals 210 and 212 and includes a triac
214 connected directly between these terminals. When suitable signals are
applied to the triac 214 from parallel connected output ports, lines PA0
and PA1 of the microcontroller 216 through a current limiting resistor
218, the triac is turned on shortly after the beginning of each half cycle
of the supply; otherwise it remains turned off. The power supply circuit
for the microcontroller is also connected across the terminals 210, and
includes a dropper resistor 220, a capacitor 222 and a zener diode 224 in
series so as to produce voltage limited negative going pulse across the
diode 224 during or at least at the beginning of each negative half-cycle
of the supply, a rectifier diode 226 and a reservoir capacitor or
equivalent 228. One terminal 210 is also connected through a resistor 248
to a mid point of a chain of resistors 230,232,234 and 236 connected at
each end to the positive and negative supply terminals VCC and VSS of the
microcontroller 216, forming two potentiometers connected respectively to
input port lines PB4 and PB5 of the microcontroller. A further input port
line PB0 is normally pulled up by a resistor 238, but may be pulled down
by the momentary contact switch 200. An output port line PA2 can sink
current through a resistor 240 and the LED 201. Reset, non-maskable
interrupt (NM1) and test terminals of the microcontroller are not used and
are grounded. A crystal 242 in conjunction with capacitors 244 and 246
connected to terminals OSC1 and OSC2 provide a clock signal for the
microcontroller. In place of or additional to the reservoir capacitor 228,
a rechargeable battery 250 may provide back-up power to the
microcontroller 216 in the event of a power failure.
Operation of the microcontroller will be readily apparent from study of the
following pseudocode listing and memory map.
As compared with the preceding embodiments, both normal switching functions
and mode switching are performed using a single momentary contact switch.
As will be apparent from study of the preceding pseudocode, a brief press
on the switch 200 (in this example less than two seconds) will merely
cause the device as a whole to toggle between an ON condition in which the
microcontroller forwards triggering pulses to the triac 214, thus allowing
current to pass between the terminals 210 (except for brief periods at the
start of each half cycle utilized to provide power to the microcontroller
through the power supply circuit already described), and an OFF condition
in which no pulses are forwarded and an open circuit times exists between
the terminals 210 (except for a minimal current flow used to power the
microcontroller). Any such activation of the switch will reverse the
condition of the device, and will also take it out of the `automatic`
mode. In order to place the device in automatic mode, the switch is
pressed for at least two seconds, and thereafter, until the switch is
again pressed to toggle the state of the device, the microcontroller will
change the condition of the device according to the data stored as to
switch transitions in the tables for three successive twenty-four hour
periods, the data in the tables relating to transitions of the type
necessary to reverse the state of the switch being logically ORed to
provide a composite switching pattern, and the timing of any transition
applied being subjected to a random variance of up to 15 minutes (in this
example). In normal mode, the tables are written to on successive days,
one at a time.
Various modifications in the program are possible within the scope of the
invention. For example, a single table each of `ON` and `OFF` transitions
could be maintained, with additions of transitions of each type beyond a
predetermined total, for example eight, resulting in the oldest stored
transition being discarded. Either system results in the stored pattern of
switch transitions being updated on a continuous basis when the switch is
in normal use, and in a composite pattern being regenerated during a cycle
automatic operation which is based upon a composite of several cycles
(usually 24 hour periods) of normal operation. This is a major improvement
over systems in which the automatic operation period is set up during an
initialization of the switch, whether the programming of the actual switch
transition times is manual or `inherent`.
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