Note: Descriptions are shown in the official language in which they were submitted.
WO 92/09899 Pcrtus91/O9OOO
2 7 l i~, ~ ~ i
~!~
DISPLAY FOR A CIRCUIT BREA~R l'RIP IJNlT
Field Of The ~nvention
The present invention relates generally to circuit breaker trip units and,
5 more particularly, to peripheral display devices communicating with circuit
breaker trip units.
Background Of The ~nvention
The practice of monitoring circuit breaker trip units is becoming
10 increasingly important. Proper monitoring can provide tangible benefits
with respect to equipment operation and maintenance; therefore,
significant return on investment. More specifically, these benefits include
savings in terms of equipment ener~y costs and maintenance costs, better
equipment utilization, and increased system reliability.
Known monitoring techniques have included a number of display
units coupled to circuit breaker trip units. For instance, fixed display units
have been permanently afflxed as part of the circuit breaker housing.
Unfortunately, this technique is disadvantageous in applications having a
multitude of circuit breakers because of the cumulative cost of each display
20 unit in each circuit breaker housin~.
Similarly disadvantageous is the remotely located display unit which
is cabled to a multitude of circuit breaker trip units. This type of
implementation is costly in terms of the excessive cables that are required
to interconnect the system, and of the labor that is required to install such
~YO 92/09899 PCr~US91/09000
2~ ~: 2
a system. Moreover, in many applications a remotely located display unit
is not practical for monitoring and servicing the circuit breaker system.
In another known monitoring technique, a portable display unit is
configured to draw power from the circuit breaker trip unit. This
5 technique is advantageous in that it overcomes many of the problems
associated with the previously discussed techniques, but is disadvantageous
in applications which require monitoring of the trip unit during system
down times; that is, when the trip unit has experienced instantaneous or
longer periods of power interruption. During these times, when power to
10 the trip unit is interrupted, power to the display unit is also interrupted.
Summary of the Invention
It is a general object of the present invention to provide a reliable,
power conservative system for monitoring the operation of a circuit
15 breaker trip unit.
It is a more specific object of the present invention to provide such
a system that can be easily retro-fit with existing circuit breaker
arrangements.
In accordance with a preferred embodiment, the present invention
20 provides a portable communica~ion device for communicating with a circuit
breaker trip unit, in which the portab]e communication device includes a
keypad, a display, an interface circuit whlch couples data sent from the
trip unit with the portab]e communication device, a contro1 circuit which
responds to the keypad and to the data sent from the trip unit for
25 controllin~ the display, a local power source which provides power to the
WO 92/09899 ~ ,~ t;~ PCI'/US91/09oO0
portable communication device, and a power switch which is responsive to
the control circuit for disabling the local power source during periods when
data is not being received from the trip unit.
S Brief D~scription Of The Drawin~s
Other objects and advantages of the invention will become apparent
upon reading the following detailed description and upon reference to the
drawings In which:
FI&. la is a schematic diagram of a portable communication device,
10 in accordance with the present invention, for monitoring a circuit breaker
trip system;
FIG. lb is a perspective view diagram of the portable
communication device shown in FIG. la; and
FIGS. 2-7 comprise a flow chart illustratin~ a preferred manner in
15 which the microcontroller of FIGS. la and lb may be programmed.
While the invention is susceptible to various modifications and
alternative fo~ns, a specific embodiment thereof has been shown by way of
example in the drawings and will herein be described in detail. It should
be understood, however, that it is not intended to limit the invention to the
20 particular fonns disclosed. On the contrary, the intent;on is to cover all
modif;cations, equivalents, and alternatives falling within the spirit and
scope of the invention as defined by the appended claims. ~ -
2S
f
w0 92~09899 Pcr/us91/osooo
(J
Descripbon Of The Preferred Embodiments
The present invention is particularly useful in industrial applications
wherein a plurality of circuit breaker trip units are periodically monitored
and serviced. In such an environment, the portabili~,r of the present
5 invention allows it to be interconnected with each trip unit sequentially so
as to minimize the number of components.
In FIG. la, a preferred embodiment of the present invention is
shown in schematic form to include a pair of push buttons 10 and 12
implementing a simple keypad, a display circuit 14, an interface circuit 16
10 coupling data sent from a circuit breaker trip unit (not shown), a
microcontroller 18 and a power control circuit 20.
The microcontroller 18, which is preferably implemented using a
Motorola 68HC7OSC8-type IC (integrated circuit), operates as the control
center for the portable communication device illustrated in FIG. 1. The
15 microcontroller 18 receives both user and trip unit type data. User data is
received by the microcontroller 18 via push buttons 10 and 12, using pull-
down 100 kOhm resistors 22-23 and a menu driven computer program
(FIGS. 2-7). Trip unit data is received by the microcontroller 18 at a
peripheral port (e.g., PD0) via the interface circuit 16, which includes a
20 fiber optic connector 26 for electrically isolating the portable
communication device of FIG. la from the trip unit, a 100 kOhm
termination resistor 28 and conventional amp]ification circuit~y for
conditioning the trip unit data for reception by the microcontroller 18.
The amplification circuitly includes a pair of operational amplifier
25 circuits and a transistor circuit. The operational amplifier circuits, which
WO 92/09899 ~ ~ 7 ~ PCr/US91/09OOo
.` 5
may both be implemented using LM358-type ICs, include an inverting
amplifier 30 and a conventional negative feedbac3c amplifier 32. The
resistor 34 in the feedback path of the inverting amplifier 30 may be
implemented using a 1.5 mega-Ohm resistor, and the amplification for the
5 amplifier 32 may be implemented usin~ a 470 kOhm resistor 36 and a 10
kOhm resistor 38. The final stage of the interface circuit 16 includes a
BS170 type FET (field-effect transistor) 40 and bias resistors 42 and 44
- having 10 kOhm and 100 kOhm values, respectively.
The power control circuit 20 is another important part of the
10 portable communication device of FIG. la. It allows the user to power-on
the portable communication device via momentaly push-button switch 50,
and allows the microcontroller 18 to automatically power-down the
portable communication device in the event that the microcontroller 18
does not re- eive data from the trip unit for a prescribed period of time.
15 This si~nificantly extends the life of the power source (battery 52~ for the
portable communication device in that it maximizes its efficiency.
More specifically, diode 54 is momentarily forward biased upon
power-up, via push-button switch 50, to allow a FET 56 to engage a
bipolar transistor 58, which in turn drives an LP2950 type five-Yolt
20 regulator 60 to provide Vcc power, using a 0.1 microFarad capacitor 62 to
suppress noise. The FET 56 may be implemented usin~ a BS170 type
component, the transistor 58 usin~ a 2N3906 type component and resistors
64, 66 and 68 using 100 kOhm, 27 kOhm and 10 kOhm values,
respectively. Once the microcontroller 18 receives operating power, it
25 drives line 72 high (via port PA1) to folward bias a diode 74, which
WO 92/098~9~,'3~ ~ PCr/US91/09000
continues to allow the FET 56 to engaBe the bipolar transistor 58 so as to
maintain Vcc. The microcontroller 18 then employs a software timer to
time periods during which no data is received by the trip unit. If the
duration exceeds a prescribed limit, the microcontroller 18 drives line 72
5 low to disengage the bipolar transistor 58 and power-down the portable
communication device so that power from the battery is not wasted.
The display circuit 14 is controlled conventionally, using the PB0-
PB7 peripheral ports of the microcontroller 18 to drive a 4 by 16 LCD
(liquid crystal display) 78, which is preferably implemented using an
10 LM73X4C16CX type component available from Densitron. A negative
voltage generator 80, such as an Intersil ICL7660 component, in
conjunction with a pair of 10 microFarad capacitors 82 and 84, is used to
provide the requisite negative voltage to the LCD 78. Resistors ~,6 and 88
may be implemented using a number of different values depending on the
15 desired bri~htness of the LCD 78. In one application, for example, 4.7k
kOhm and lk kOhm values may be used for resistors 86 and 88,
respectively.
FIG. lb illustrates a preferred embodiment of the portable
communication device from a perspective view. The device incJudes an
20 enclosed housin~ 90, an optical waveguide 92, a battery compartment 94,
and the switches 10, 12, 50, the display 78 and the connector 26, discussed '
above in connection with FIG. ~a. - ,
FIGS. 2-7 comprise a flow chart for implemen~ing the
microcontroller 18 of FIG. 1. More specifically, FIG. 2 represents a flow
25 chart for the main operating progMm of the microcontroller. FIGS. 3 anL3
WO 92/09899 2 ~ Pcr/Us9]/o9ooo
S constitute respective flow charts for interrupt routines which are
respect;vely serviced in response to a timer which is inten~a] to the
microcontroller and in a response to data being received from the trip unit
via the SCI port of the microcontroller. The remaining charts depicted in
5 FIGS. 4 and ~7 are subroutines which are respectively called in response
to the reception of data messages, for periodically looking for keypad data
and for periodically contro]ling the display.
The flow chart of FIG. 2 be~ins upon power-up as depicted at block
100. At blocks 102 and 104, the microcontrol]er initializes its various ports
10 and system variables, including driving the output line (72 of FIG. la),
which maintains the local power source in the "on" condition.
At block 106, the microcontroller performs a test to determine if its
SCI data register is full. If the SCI data register is full, flow proceeds from
block 106 to block 108 where the subroutine of FIG. 4 is serviced. Upon
15 returning from the subroutine of FIG. 4, or from block 106 if the SCI data
register is not full, flow proceeds to block 11û.
At block 110, the microcontroller performs a test to determine if
the display reset timer has timed out. The display reset timer from block
110 and other timers to be discussed in connection with this flow chart of
20 FIG. 2 are controlled using the interrupt service routine of FIG. 3. The
display reset timer is used to indicate when the display (7~ of FIG. la) is
ready to be controlled after power-up, since a 15 millisecond post-power-
up delay is specified for the preferred LCD component. Accordingly, if
the display reset timer is equal to 0, then the 15 millisecond delay has
- . . .. . ..
-- .
. .
wo 92/09899 ~ ~ c3 ~ Pcr/us9l/o9ooo
elapsed, and the microcontroller proceeds to block 112 to reset the LCD in
preparation for subsequent use and to disable the timer.
At block 114, the microcontroller deterrnines whether or not it is
time to service the keypad. A keypad service timer, which is a]so
5 maintained using the interrupt service routine of FIG. 3, is regularly
decremented until it reaches 0, at which time the microcontroller proceeds
to deterrnine if any data had been entered via the keypad. Thus~ at block
116 the microcontroller performs a test to determine if all the keys have
been serviced. This is determined by checking if the key-ready flag is set
(see FIG. 6). If all the keys have been serviced, flow proceeds to block
118 where the microcontroller calls the keypad service subroutine of FIG.
6. From block 118, or if all the keys have not been selviced at block 116,
flow proceeds to block 120 where the keypad selvice timer is restored to
its original value. From block 120, flow proceeds to block 122.
At block 122, a test is performed to determine if the display reset
timer has been disabled. If the display reset timer has been disabled, then
- the 15 rnillisecond delay after power-up has elapsed, and flow can proceed
to block 124 where the display service subroutine of FIG. 7 is called for
servicing the LCD.
At block 126, a test is performed to determine if the prescribed
time period, durin~ which no trip data has been received, has lapsed. A
shut down timer, contro]]ed by the routine of FIG. 3, is used for this
purpose as depicted in b]ock 126. If that prescribed peAod has ]apsed,
flow procecds to block 128 where the appropriate power control bit (line
72) is set ]ow to shut down power to the portab]e communication device.
WO 92/09899 2 ~ 2 ~3 ~ Pcr/us9l/
From block 128, or in response to the shut down timer not being
decremented to 0, flow returns to block 106.
The timer interrupt selvice routine, which is depicted in FIG. 3,
occurs each millisecond. The flow chart begins at block 132 and, at block
S 134, the microcontroller sets the output compare register to interrupt at
the next millisecond.
At blocks 136, 138 and 140, the display-reset, keypad service and
125-millisecond timers are decremented. The 125-millisecond timer is used
to decrement the shut-down timer and the display timer, which have
10 relatively long time periods. At block 142, the microcontroller performs a
test to determine if the 125-millisecond timer has been decremented to 0.
lf so, the 125-millisecond timer is refreshed and flow proceeds to blocks
144 and 146 to decrement the display and shut-down timers. From block
146, and from block 142 if the 125-millisecond timer has not been
15 decremented to 0, flow proceeds to block 148, where the microcontroller
executes a return from interrupt command.
FIG. 4 illustrates a preferred manner of implementin~ bloclc 108 of
FIG. 2: the SCI data subroutine. The subroutine is entered at block 152,
and, at block 153, the microcontroller interprets the data packet received
20 Yia the SCI port. The received data packet may be related to
confi~uration data or operating-status data. Each such type of data
corresponds to the type of multi-byte packet that is being sent from the
trip unit. For further infonnation concerning the data packet structure,
reference may be made to copending U.S. Patent Application No.
25 07/503,267, filed on April 2, 1990, incorporated in its entirety by reference.
WO 92/09899 ~ c~ PCr/lJSg1/09000
If the received data is configuration data, flow proceeds from block 153 to
block 154 where the configuration data memory locations are updated. lf
the received data is not confi~uration data, flow proceeds from block 153
to block 155 where a test is performed to determine if it is status data. If
5 so, the status data memory locations are updated at block 156. At block
157, the microcontroller updates its record of the trip status. As discussed
in the above copendin~ application, the trip status includes long time trip,
short time trip, instantaneous trip, ~round fault trip and normal operation.
At block 158, the microcontroller clears the SCI data ready fla8 so that it
10 can be informed the next time a data packet h s been received via the SCI
port. The microcontroller then executes a return from subroutine
command, as depicted in block 160.
FIG. 5 illustrates the SCI interrupt routine, which is serviced each
time a byte is received via the SCI port. Upon enterin~ the routine at
lS block 164, the microcontroller performs a test to determine if any errors
have been received, depicted at block 166. If one or more errors were
received via the SCI port, flow proceeds from block 166 to block 168
where the microcontroller resets the SCI port and an associated messa~e
byte counter, which is used to track how many bytes of a particular packet
20 had been re~eived so that errors are not accumulated. From block 168,
flow proceeds to block 170 where the microcontroller refreshes the
shutdown timer, since data has been received from the trip unit, and the
portable communication device of FIG. la need not be powered down.,
From block 170, flow proceeds to block 172 where the microcontroller
25 executes a return from interrupt command.
Wo 92/09899 ~ iv ~ fJ i~ Pcr/us9l/o9ooo
If errors are not detected via block 166, flow proceeds to block 174
where a test is performed to determine if the received data byte constitutes
the beginning of a data message. If not, flow proceeds to block 176 where
the microcontroller stores the data byte and increments the data byte
5 counter in order to track the number of received bytes in the instant
packet. From block 176, flow proceeds to bloclc 178 where a test is
performed to determine if the received byte constitutes the end of a data
message or packet. If the received byte does constitute the end of a data
message, flow proceeds to b]ock 180 where a test is perfonned to
10 determine if there are any byte or bit errors in the packet that has been
received. This is preferably done by performing a conventional checksum
test. If the checksum test passes, flow proceeds to block 182 where the
microcontroller sets the SCI data ready flag of block 158 (FIG. 4) to
record that a paclcet has been received. From block 182, flow proceeds to
15 previously discussed block 168.
If the microcontroller determines that the received byte is the
beginning of a data message or packet, flow proceeds from block 174 to
block 184 where the microcontroller begins to form the packet by storing
the be~inning of the message and resetting the byte counter indicating the
20 number of bytes that have been received for the packet. From bloc3c 184,
from block 178 if the received byte constitutes the end of a data message
and from block l80 if the checksum test fails, flow proceeds to block 170
to refresh the shutdo~n timer before returning from the interrupt routine.
FIG. 6 illustrates the keypad service subroutine depicted in block
25 ~18 of FIG. 2. After entering the routine at block 188, flow proceeds to
'` W0 92/09899 ~ 12 PCr/US91/09000
block 190 where the microcontroller reads the port at which the keypad
(set of push-button switches) is connected. At block 192, the
microcontroller determines if a push-button switch has been depressed or
released by comparing the present state of the push-button switch port to
S its previous state. If the present and the previous states of the push-button
switch port are the same, f30w proceeds from block 192 to block 194 where
the microcontro]ler executes a return from subroutine command.
If the microcontroller determines that a push-button switch has
been depressed or released, flow proceeds from block 192 to block 196
10 where the microcontroller once a~ain reads the same port At this point in
the flow chart, the microcontroller initiates a s vitch debouncing procedure.
If the microcontroller reads the push-button switch port three times and
concludes that the data in the port has not changed at each one of the
three reads, then the switch has been debounced. Thus, from block 196,
15 flow proceeds to block 198 where the microcontro]ler makes the first
comparison. From b]ock 19B, flow proceeds to block 200 if the successive
data port reads are not the same.
At block 200 a counter, which is used for tracking the number of
times the comparison has been made, is cleared. If the success reads at
20 block 198 are the same, flow proceeds from block 198 to block 202 where
the counter is incremented.
From block 202, flow proceeds to block 204 where a test is
performed to determine if three successive reads have taken place with the
same data being read at the port. If not, flow returns from block 204 to
25 block 196 for the next successive read of the push-button switch port.
WO 92/09899 Pcr/ussltog
13
From block 204, flow proceeds to block 206 where a test is
performed to determine if the push button switch has been released. If
the push-button switch has been released, flow proceeds to block 208
where the microcontroller updates a register storing the status of the
5 associated push-button switch and sets a key ready flag to record that a
switch has been pressed and released, the latter of which must happen for
the microcontroller to act on the data input by the user. From block 206,
if the switch has not been released by this time, flow proceeds to block 194
where the microcontroller executes a return from subroutine command.
FIG. 7 illustrates the display service subroutine which is depicted at
block 124 of FIG. 2. The subroutine of FIG. 7 changes inforrnation on the
display in response to: the 500 millisecond timer timing out, a user request
via ~he kegpad, or trip unit data requiring a change. Preferably, there are
two types of display modes, a current-related mode and a configuration
15 mode with SLY subtypes associated with the configuration mode. The
current-related information mode displays the amperage for each of three
phases plus ground fault. The configuration submodes display: (1)
identification of breaker type, current sensor size and amperage rating; (2)
~ong time trip settings, pick-up settings in amperes and in time; (3) short-
20 time trip settiDgs, pick-up settings in amperes and in time; (4)
instantaneous trip settings and associated pick-up settinL~s; (5) ground fault
trip settings and associated pick-up settings; and (6) the revision number
for the hardware and firmware.
After entering the subroutine at block 210 of FIG. 7, flow proceeds
25 to block 212 to determine if a nag has been set, which flag indicates that
O 92~09899 t ~ PCT/US91/09000
14
another portion of the display needs to be written. Only one portion of
the display is written at a time. If other portions of the display have not
been written, then the display is still in progress. If another display portion
needs to be written, flow proceeds from block 212 to block 214 where the
5 microcontroller updates the display using conventional line-by-line LCD
writing techniques. From block 214, flow proceeds to block 216 where the
microcontroller performs a return from subroutine command.
From block 212, flow proceeds to block 218 if a display update is
not in progress to determine if the key-ready flag is set (see block 208 of
10 FIG. 6). If the key-ready flag is set, then a key or switch was detected as
being depressed and released, and flow proceeds to block 220.
If the key-ready flag 2s not set, flow proceeds from block 218 to
block 2æ where the microcontroller performs a test to determine if
current-related information is being displayed; for example, the display of
15 current in each of the three phases and ground fault.
If the display is not displaying current-related information, flow
proceeds from block 222 to block 224 where the microcontroller performs
a test to determine if the display is displaying configuration information
and the configuration requires changing. If at least one of these conditions
20 is not met, no further action is necessary and 90w proceeds to b]ock 216
for exiting the subroutine. If both of these conditions are met, flow
proceeds from block 224 to block 226 where the microcontroller sets up
for writing the new configuration. This may be done by writing a portion
of the new display during this visit to the display service routine and the
WO 92/09899 15 2 ~ 7 ,~, ~t !~
remaining portion during the next visit. From block 226, flow proceeds to
block 214 for writing the new configuration data on the display.
~ rom block 222, flow proceeds to block 228 if the information bein~
displayed is current-related information. At block 22~, the current-related
S information is set for being updated (or refreshed) by setting a flag to
record that updates should only pertain to the numbers, e.g., the displayed
amperages for the various phases and ground fault. This updating or
refreshing in the display mode for "current" is set to occur every 500
milliseconds. From block 228, flow proceeds to block 214 for the actua]
10 refreshing of the current-related information on the display.
At block 220, if the push-button switch corresponding to a function
key is detected as being depressed and released, flow proceeds to block
232 where the microcomputer toggles the display from the configuration-
type display to the current-related information display or vice-versa. From
15 block 232, flow proceeds to block 214 where the display is actually written
to for the change indication of block 232.
From block 220, flow proceeds to block 233 if the function switch
was not engaged. At block 233, a test is performed to determine if
current-related information is being displayed. If so, en~agement of the
2û other switch, which activated the key ready flag, was improper and flow
proceeds to block 216. From block 233, flow proceeds to block 236 if the
microcontroller determines that the display is not displayin~ current-related
information.
At this point, the microcontroller has determined that a switch was
25 depressed and released (block 218) and that it was not the "function"
?J~r~ J~ 16 PCI/US91/09000
switch (block 22~). Since the only other switch is the "select" switch, the
microcontroller deduces that the "select" switch has been depressed and
released. The "select" switch is engaged by the user when it is desired to
switch to the next of the six submodes of the configuration mode. If the
5 last of the six submodes is displayed when the "select" switch is en~aged, a
transition to the first submode is displayed. From block 236, flow proceeds
to blocks 232 and 214 to chan~e the display.
While the invention has been particularly shown and described with
reference to a particular embodiment, various modifications may be made.
10 For example, the microcontroller (or microcomputer) 18 of FIG. la may
be implemented using discrete circuits. Further, rather than reactivating
power solely by the switch 50 of FIG. la, power may be continuously
provided from the battery to a data sensing circuit, such as the interface
circuit 16 of FIG. la, so that the data sensing circuit momentarily forward
15 biases the diode 54 to initiate power to the device of FIG. 1. A
conventional "one-shot" circuit may "OR"-tied with the switch S0 to couple
the data sensing circuit to the diode 54. It will be recognized by those
skilled in ~he art that such modifications and changes may be made to the
present invention described above without departing from the spirit and
~0 scope thereof.
- ` ;
,
