Note: Descriptions are shown in the official language in which they were submitted.
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A PROGRAMMABLE MESSAGE DISPLAY
This invention relates to an electronic control system, in
particular to a programmable electronic display module, or
package, for presenting programmed messages to an operator of an
apparatus or process, which are indicative of any variance in the
routine operation of the apparatus, or in the normal steps of the
process, in order to inform and prompt the operator to take
action to correct the situation.
In the control of modern automated machinery, apparatus and
processes, it is convenient and often necessary to present
messages to an operator which indicate equipment status, indicate
fault conditions or prompt the operator to perform other
actions. These messages often have to be programmed or
customized to the specific machine, apparatus or process being
controlled and it may very well be desirable to alter the content
of the programmed messages at some point in time to accommodate
improvements or changes in the machinery, apparatus or process.
A message display which is programmable and is also erasable for
changing programs, and one which displays both alphabetical and
numerical strings of characters, is suited to many of these
applications, and is a useful tool for the operation and control
of the apparatus or process.
Currently, available programmable message displays typically
require a complex electrical interface, such as a RS232 computer
cable, to the host controller. The interface may be an industry
standard or priority, serial or parallel specification. The
interface often requires a special communications module to be
installed in the host controller which adds hardware complexity
and expense. On the display itself, the complexity of the
interface hardware and connection terminals makes it necessary to
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use a large display enclosure and associated operator's panel
space.
One of the objects of the invention is to present messages to
the operator through an electronic display such as a video
display, or a light emitting diode (LED) display, or preferably a
liquid crystal display (LCD), or some other state of the art
visual display.
Another object of the invention is to present messages to the
operator through the electronic display which are programmed into
a removable erasable programmable read-only memory device
(EPROM), which is then mounted to a socket on a circuit board in
the display.
Another object of the invention is to program alpha-numeric
messages into the EPROM which are between 64 to 320 messages on
two lines with sixteen characters on each line.
Ar,other object of the invention is to provide the electronic
display as a module, or package, which can be used as an
auxiliary component of a central processing unit (CPU) or other
programmable digital controller based electrical system, or a
programmable logic chip (PLC).
Another object of the invention is to provide a housing for
the programmable electronic display which is adapted for panel
mounting to a console or to the surface of the apparatus.
And, another object of the invention is to provide a simple
interface of two signal wires and a common line at a +12 VDC
level for a sink mode or at a 0 volt level for a source mode.
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Typically, the machine, apparatus or process, which is to be
operated and monitored, has an electrical control system which
contains the CPU, or PLC or some other type of digital based host
controller. The programmable electronic display module is
interfaced with the host controller, which has an additional
function of selecting the code for a particular programmed
message to be displayed.
Once the code for the message has been identified in the
host controller, and by means of the simple serial communications
wiring, the code is transmitted to the EPROM of the display
identifying and retrieving the particular programmed message,
which is then displayed on the LCD.
The programmable message display module can be mounted to a
console, panel or to the surface of the apparatus and is used to
display the programmed messages at the request of the CPU, or the
PLC, or other host controller.
The display employs a commercially available low-cost wide
angle liquid crystal device in the message output window. It is
to be understood that the display may be a video display, or a
LED display, or some other state of the art visual display.
The display supports a 128 character ASCII (American Standard
Code For Information Interchange) set which includes both
alphabetical and numerical characters; and shows key words and
numbers to inform and prompt the operator to take appropriate
action for controlling the operation of the apparatus or process.
Each message is 2 lines by 16 characters. Up to 64 messases
can be displayed with a 2764 EPROM memory device, and up to 320
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messages can be displayed with a 27128 EPROM memory
device. Blinking messages, as well as alternating
messages, allow up to 64 character messages. The
display is powered from any 8 to 15 VDC power supply.
Communication to the display from the host
controller is by means of a simple two signal interface.
One line (enable) is to request a message and another
line (count) is to specify the message number.
The two signal lines may be of either source or
sink type which makes the display compatible with
virtually any host controller. A common line is
provided which is at a +12 volt level for the sink mode
or at a O volt level for the source mode. A small
terminal strip is provided at the rear of the display
for quick, easy connections of power and signal inputs.
Reference is now directed to the various figures of
the drawing wherein:
Fig. 1 illustrates the signal and common line
connections of the programmable electronic display
package to the host controller, and the electrical power
connection of the power supply to the programmable
electronic display package;
Fig. 2 is a top view of the electronic display
package showing the terminal strip;
Fig. 3 is a typical EPROM device;
Fig. 4 is a bottom view of the display package
shown in Fig. 2 illustrating a schematic of the
electronic circuitry;
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Fig. 5 is an illustration of three wave forms; and
Fig. 6 is a simplified flow chart of the program
performed by the microprocessor shown in Fig. 4.
The operation of the system and the programmable
electronic display 12 will now be explained.
A programmed EPROM 10 is inserted into a vacant
twenty-eight pin socket (not shown) on a circuit board
(not shown) housed in the display module 12. The DC
power source module 14 is connected by two electrical
wires 15 and 17 to the 12V and GND (Ground) screw
terminals 18, 20 of the terminal strip 16. A DC current
of approximately 180 milliamperes at 12VDC is required
to operate the electronic display. The terminals of the
two signal lines EN (enable) 22 and CNT (count) 24 are
connected by electrical wires 26, 28 to the output
terminals 30, 32 of the host controller 34. The count
and enable inputs on the electronic display sink or
source at approximately 10 milliamperes of the DC
current. A third electrical wire 36 connects the COM
(common) terminal 38 on the electronic display terminal
strip 16 to common voltage output terminal 40 on the
host controller 34.
When the DC power module 14 is turned on, the EPROM
10 delivers an introductory message which is displayed
on the LCD 40 for approximately two seconds, and then
the EPROM clears the display.
In order to monitor the operation of the apparatus
or process, an enabling signal is first received by the
host controller 34 from the apparatus or process. A
pause of approximately two milliseconds follows the
receipt of the enabling signal (Fig. 5). Then a count
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signal (Fig. 5) between 1 and 320 pulses is sent to a
counter in the display package 12. The number of the
pulses correspond to the code number of the designated
programmed message which is to be displayed on the LCD
40. The counter counts the transmitted pulses and, after
a timed preset pause (Fig. 5) following the last pulse
of the train of pulses, the total count is transmitted
to a comparator which compares the total count with an
index of the code numbers of the programmed messages in
the memory of the EPROM. The appropriate message is
then retrieved from the memory of the EPROM and
transmitted to the display window of LCD 40. The LCD 40
continues to display the message until the enabling
signal is turned off resetting the host controller 34.
No delay is required between the enable line and
the count line. There is a maximum of 1000 Hz count
line toggle rate. The EPROM has an access time of 250
nanoseconds or less.
The programmable electronic display system
described above can send both enable and count signals
over the same line. An enable/count signal line held
logic low level for preset time (TR) causes the
programmable electronic display circuitry to disable and
clear its display. Any deviation from logic low level
is considered a count pulse on the leading edge of
transition from logic low to logic high level.
An enable/count signal remaining at logic high
level more than the preset time (TF) indicates that the
total message from the address of the programmed message
in memory has been received and should be indexed from
the EPROM and displayed.
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In summary, one of the advantages of the system and
the programmable electronic display module is that a
costly parallel signal interface or a complex RS-
232/ASCII serial interface is not required.
Another advantage is that the programmable message
controller with alphabetical and numerical display
requires only two signals to transmit the message
selection data, i.e
- the enable signal which allows the message
controller to start looking for and counting
pulses on the count signal input line; and
- the count signal which contains the actual
message number as a simple serial string of
pulses, for example, five pulses represents
message five, ten pulses represents message
ten and so on.
