 |
Description  |
|
|
BACKGROUND OF THE INVENTION
The present invention relates to remotely controlled power switching
devices, and more particularly, to circuitry for selectively applying
power to one or more of a group of load devices by toggling a remotely
located manually operable switch.
The energy shortages which have occurred in recent years and corresponding
increases in cost of energy, such as the electrical power supplied to
residential structures, are well known. In response to the increased
costs, many people have set their air-conditioning thermostats at higher
temperatures to reduce energy consumption. Many people have also turned to
the ceiling paddle-type fans for providing greater air circulation which
greatly improves the comfort at the higher temperatures.
A problem which has increased the cost of installing these ceiling fans,
especially in an existing structure, has been the additional wiring and
control switches which must be installed. One way of avoiding the extra
wiring costs is to remove a ceiling light fixture and install the fan in
its place so that the original switch and wiring may be used for the fan.
This approach has several deficiencies. The first is the obvious loss of
the light fixture. Many fans are provided with a built-in light fixture
but if the fan and light fixture are to be separately controlled, the
additional line is still needed. Also, many of the ceiling fans have two
or more speeds of operation so that a multiple position switch and extra
cabling is normally required to allow selection of fan speed from the wall
mounted switch. Thus, it can be seen that it would be desirable to provide
an arrangement with which a ceiling fan may be installed in place of a
single light fixture and multiple loads such as both the fan motor and a
built-in light fixture could be selectively controlled from an originally
installed manually operable switch connected to the fan by a single
two-conductor transmission cable.
SUMMARY OF THE INVENTION
Accordingly, an object to the present invention is to provide circuitry for
selectively applying electrical power to one or more of a group of load
devices under control of a remotely located manually operable switch.
Another object of the present invention is to provide a remote load
selector device which allows the selective application of electrical power
to multiple loads, such as a ceiling fan and its built-in light fixture,
when such loads are installed in a pre-existing outlet to which power is
supplied under control of a single manually operable switch.
The selective application of electrical power to one or more of a plurality
of load devices is achieved by providing circuitry, including an
electronically controllable power switch for each load device and control
circuitry having an input adapted for coupling to a remotely located
manually operable switch by a single two wire power transmission cable and
having outputs for controlling the states of the power switches in
response to actuation or toggling of the manually operable switch.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be better understood by reading the following
detailed description of the preferred embodiments with reference to the
accompanying drawings wherein:
FIG. 1 is a block diagram illustrating the coupling of a remote load
selector according to the present invention to a manually operable switch
and a plurality of load devices;
FIG. 2 is a block diagram showing the installation of the remote load
selector according to the present invention in a second typical house
wiring arrangement; and
FIG. 3 is a detailed schematic diagram of a preferred embodiment of the
present invention adapted for selectively controlling application of power
to two load devices.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
With reference now to FIG. 1, the installation of a remote load selector,
indicated by the block 10, in a typical residential lighting circuit is
illustrated. A typical two wire 110 volt power transmission line is
indicated by the hot conductor 12 and the common conductor 14. In a
typical lighting circuit, the hot conductor 12 is connected to one
terminal of a single pole, single throw wall switch 16. The other terminal
of switch 16 is typically connected to a conductor 18 which together with
an extension of the common line 14 forms a power transmission line which
runs from the location of wall switch 16 to the location of a ceiling
fixture such as a light fixture. In the present invention, a plurality of
load devices 20, 21 is installed in place of a single load device such as
a light fixture. The conductor 18 is connected to one terminal of each of
the load devices 20, 21. In addition, the conductor 18 is connected to an
input terminal 19 of the load selector device 10. In a standard wiring
arrangement, the second terminals 22, 23 of load devices 20 would each be
connected to the line 14. In such an arrangement, all devices 20, 21 would
be turned on and off simultaneously under control of switch 16. According
to the present invention, the second terminals 22, 23 of load devices 20
are connected to power terminals of the load selector 10 and the common
line 14 is connected to another power terminal 24 of selector 10. The load
selector 10 includes electronically controllable power switches for
selectively completing circuits between the second terminals 22, 23 of the
load devices 20 and the common line 14. The details of a preferred load
selector device 10 will be described with respect to FIG. 3.
With reference now to FIG. 2, the installation of the load selector 10 in a
second commonly encountered house lighting circuit is illustrated. In FIG.
2, the incoming power line comprising the hot lead 12 and common lead 14
are brought in to the location of the ceiling light fixture rather than
the location of the wall switch 16. In such an arrangement, the common
lead 14 is typically connected to one terminal of the load device and the
second terminal of the load device or devices is usually connected to one
conductor of a two conductor line connected to the wall switch 16. The hot
line 12 is then typically connected at the location of the ceiling fixture
directly to a second lead, such as lead 18 of the two wire line running to
the switch 16. The load selector 10 of the present invention may be
installed in such an arrangement as shown in FIG. 2. In this arrangement,
the common lead 14 is connected to the first terminals of each of the load
devices 20, 21 and also continues to one terminal of the switch 16. The
hot line 12 is then connected to the terminal 24 of load selector 10 and
the second line 18 from the switch 16 is connected to the remaining
terminal 19 of the load selector 10. As will be seen below, the identical
load selector 10 may be used in either of these commonly encountered
wiring arrangements.
With reference now to FIG. 3, a detailed schematic diagram of a remote load
selector is illustrated within the dotted line box 10. The remaining
portions of the circuitry correspond to the FIG. 1 installation and carry
corresponding designation numbers. The remote load selector includes power
terminals 26 and 28 connected to the second terminals 22, 23 of load
devices 20, 21. Electronically controllable power switch devices Q3 and Q4
are connected between the power terminals 26 and 28 respectively and the
terminal 24 of selector 10. As indicated by the schematic diagram, the
devices Q3 and Q4 are bidirectional thyristors. In the preferred
embodiment, devices Q3 and Q4 were commercially available devices sold by
Teccor Electronics Inc. of Euless, Texas under the part number Q4010L4.
Other similar devices could of course be substituted. Each of the devices
Q3 and Q4 is bypassed by R-C circuits comprising devices R10 and C5 and
R11 and C6 respectively. In this embodiment, devices R10 and R11 have
values of 330 ohms and devices C5 and C6 have values of 0.047 microfarads
with these values selected to prevent false triggering of devices Q3 and
Q4. Gate inputs of each of the devices Q3 and Q4 are connected through
resistors R7 and R9 respectively to collectors of transistors Q1 and Q2.
Resistors R7 and R9 have values of 300 ohms selected to provide gate
currents in the range of twenty-five to thirty milliamperes. The emitters
of transistors Q1 and Q2 are connected to a reference voltage terminal 30.
The bases of transistors Q1 and Q2 are connected to resistors R6 and R8,
which in this preferred embodiment each have a value of 20 kilohms. In the
preferred embodiment, transistors Q1 and Q2 were of the commonly available
2N2222 type.
The reference voltage of node 30 is provided by circuitry on the left side
of FIG. 3. The series combination of a current limiting resistor R1 and a
diode D1 is connected between the power line 18 and node 30. In the
preferred embodiment, resistor R1 has a value of 1 kilohm and diode D1 is
a commonly available 1N4005 type. Diode D1 provides a half-wave rectified
voltage signal on node 30. A regulating diode D2 is connected between the
node 30 and a second node 32 which is connected to the input 24 of the
load selector 10. In the preferred embodiment, diode D2 has a breakdown
voltage of thirteen volts. A capacitor C1 is provided in parallel with
diode D2 to provide smoothing of the half-wave rectified signal. Capacitor
C1 in the preferred embodiment has a value of 220 microfarads. Diode D2,
together with capacitor C1, therefore provides a somewhat regulated DC
voltage of about thirteen volts between nodes 30 and 32. It will be noted
that this is the voltage which appears across the circuits comprising the
gates of switching devices Q3 and Q4 and the transistors Q1 and Q2
respectively.
A first transition detecting circuit includes a diode D3, resistor R2, and
capacitor C3 connected in series between nodes 32 and 30. In the preferred
embodiment, diode D3 is a commonly available 1N4148 type, resistor R2 has
a value of 1 kilohm, and capacitor C3 has a value of 22 microfarads. A
resistor R4 having, in the preferred embodiment, a value of 10 kilohms is
provided in parallel with capacitor C3 to discharge the capacitor whenever
the supply of power is discontinued. A Schmitt trigger circuit U1 has an
input connected to the node 34, which is common to resistors R2 and R4 and
capacitor C3. In the preferred embodiment, Schmitt trigger U1 was a
Motorola Semiconductor type MC14584B known more commonly as a type 4584
Schmitt trigger. Other similar Schmitt trigger devices or one shot type
devices could be substituted. The output of Schmitt trigger U1 is coupled
to the clock inputs of two flip-flops U2 and U3 described in more detail
below.
A somewhat regulated voltage is provided on a node 36. A diode D4 of the
same type as diode D3 is connected between node 32 and node 36. A
capacitor C2, preferably identical to capacitor C1, is connected between
node 36 and node 30. A resistor R3 is connected in parallel with capacitor
C2 to bleed off the charge on capacitor C2 when the main power supply is
removed. In the preferred embodiment, resistor R3 has a value of 10
kilohms. The voltage on node 36 is a fairly well regulated voltage near 12
volts and is used to supply power to the logic devices U1, U2, and U3. A
second transition detector comprising the series combination of a
capacitor C4 and a resistor R5 is connected between nodes 36 and 30. In
the preferred embodiment, capacitor C4 has a value of 22 microfarads and
resistor R5 has a value of 10 kilohms. The circuit comprising capacitor C4
and resistor R5 acts as a differentiator to provide an impulse on the node
38 common to the two elements in response to a positive transition on node
36. Node 38 is connected to the reset input of flip-flop U2 and to the set
input of flip-flop U3.
The flip-flops U2 and U3 are both preferably part of a single integrated
circuit sold by the Motorola Semiconductor Corporation under part number
MC14027B and generically known as a type 4027. Other similar devices such
as an RCA type CD4027AE may also be employed. As illustrated in the
drawing, the Q outputs of flip-flops U2 and U3 are connected to the
resistors R6 and R8 respectively and thereby to the bases of transistors
Q1 and Q2 respectively. The Q output of flip-flop U3 is also connected to
the J input of flip-flop U2. The Q output of flip-flop U2 is connected to
the J input of flip-flop U3. The K input of both flip-flops U2 and U3 are
connected to the node 36. The set input of flip-flop U2 and the reset
input of flip-flop U3 are connected to the reference node 30 to prevent
activation of these functions.
With reference now to FIG. 3, the operation of the remote load selector of
the present invention will be described. When it is desired to supply
power to one of the loads 20, 21, the switch 16 is manually closed. Upon
this occurrence, a positive voltage appears on nodes 32, 34, and 36
relative to the reference node 30. This step increase on node 36 is
differentiated by capacitor C4 to provide an impulse on node 38 which
resets flip-flop U2 and sets flip-flop U3. As a result, the Q output of
flip-flop U2 is at a high level and turns on transistor Q1, which draws
current from the gate of thyristor Q3 which is thereby actuated and
supplies power to load 20. Flip-flop U3, on the other hand, provides a low
level Q output and, as a result, transistor Q2 draws no current from
switching device Q4 and its load 21 remains without power. Upon the
initial closing of switch 16, a positive voltage step also occurred on
node 34 which caused a negative step on the output of Schmitt trigger U1
which has no effect on the clock inputs of flip-flops U2 and U3 which
respond to positive going transitions only.
The user may desire to supply power to the second load 21 and may do this
by momentarily opening switch 16 and reclosing it, or in other words,
toggling the wall switch. When wall switch 16 is opened, the voltage on
node 32 relative to node 30 drops quickly to zero as a result of
conduction through the gate circuit of one or both of switching devices Q3
and Q4. Shortly thereafter, the voltage on node 34 also drops to zero as a
result of the resistor R4 bleeding the charge from capacitor C3. The time
constants are selected so that momentary line drop-outs will not cause a
significant drop in voltage on node 34. In addition, the time constant of
the R3-C2 combination is selected so that the voltage on node 36 remains
high relative to node 30 for a much longer time than the voltage on node
34. In response to the drop in voltage on node 34, the Schmitt trigger U1
provides a positive going transition on its output which clocks both
flip-flops U2 and U3. At the time of receiving this clock signal, the J
inputs of both flip-flops are low and the K inputs are both high. As a
result, the Q outputs of both flip-flops are in a high state after the
first clock pulse. Therefore, in this second state, the flip-flop outputs
drive both transistors Q1 and Q2 into conduction to, in turn, activate
both the switching devices Q3 and Q4 and supply power to both loads 20 and
21, when the wall switch 16 is again closed. Thus, the change of state of
the storage or memory devices U2 and U3 occurs very shortly after switch
16 is opened, and if switch 16 is reclosed before the voltage level on
node 36 drops sufficiently to deactivate the logic circuitry, both loads
20 and 21 will be turned on when the switch is reclosed.
If it is desired to supply power to load 21 only, the switch 16 is again
toggled, that is opened momentarily and reclosed. Upon this second opening
of switch 16, the Schmitt trigger U1 again generates a clock signal which
is supplied to both flip-flops. Upon receipt of this second clock signal,
it will be seen that both the J and K inputs of flip-flop U2 are high and
this device acts as a toggle flip-flop under these input conditions. As a
result, the Q output goes low deactivating transistor Q1 and device Q3. At
the time of the second clock signal, the J input to flip-flop U3 was low
and the K input was high so that the output state remains unchanged and
transistor Q2 continues conducting and, in turn, activating switching
device Q4. Thus, it is seen that upon toggling switch 16 a second time,
power is supplied only to load 21.
If it is desired to return to the original state in which only load 20 is
turned on, this can be achieved in two ways. In the first way, the switch
16 may simply be toggled a third time. In the third state in which only
load 21 is activated, it will be seen that the J and K inputs of both
flip-flops are high. As a result, both flip-flops toggle upon receipt of
the third clock signal with the result that the device is returned to the
first state in which the Q output of U2 is high and the Q output of U3 is
low. The three step sequence can be repeated by continuous toggling of
wall switch 16.
The device can also be returned to the original or first state by opening
wall switch 16 for a time period which is sufficiently long to allow node
36 to discharge. When power is reapplied to the circuit, the capacitor C4
then causes the flip-flops U2 and U3 to reset in the state one condition
in which only load 20 is turned on.
In an anticipated use, the load 20 may be a light fixture attached to a
ceiling fan and load 21 may be the fan motor itself. The unit will operate
as a simple light fixture under the typical condition in which a person
enters a room and actuates switch 16 to provide lighting for the room. In
the less frequent circumstance in which the person also wishes the fan to
be activated, a switch 16 must be turned on and then toggled once, that
is, turned off and quickly turned back on. By this operation, both the
light and the fan will operate. If it is desired to have the fan operate
without the light being on, the switch is simply toggled one more time and
the fan will continue to run but the light will be turned off. Both the
fan and the light may be turned off at any time simply by opening switch
16 in the normal manner.
It will be appreciated that the loads 20 and 21 could be separate windings
in a two speed fan motor and a single toggle flip-flop clocked by Schmitt
trigger U1 could be employed to alternately supply power to one or the
other of the two windings. It will also be appreciated that more than two
loads can be selectively powered according to the present invention by use
of more flip-flops or shift register circuitry controlling a larger number
of power switching devices.
It can also be seen that a circuit of FIG. 3 operates in exactly the same
manner if incorporated in the circuit arrangement of FIG. 2. In that
circumstance, the reference nodes 30, 32, 34 and 36 all float on the 110
volt power line signal, but this does not effect the operation as
described.
While the present invention has been illustrated and described in terms of
specific apparatus and methods of operation, it is apparent that numerous
other modifications and changes can be made within the scope of the
present invention as defined by the appended claims.
* * * * *
|
|
 |
|
 |
Description |
|
