A Versatile Event Counter/Totalizer Featuring,19999 Counts with Overrange Indication, or 9999 Counts with Cascade Output, Contact Closure or Logic Signal Input, High Contrast LCD, AC Powered with Ooutputs for User Supplied NI-CAD Battery Back-Up.
DESCRIPTION
Texmate's model PC-45XAC event counter/totalizer is a versatile, low cost AC powered LCD meter which features three user programmable count inputs and count rates. All count inputs are compatible with open collector sensing devices. The standard low range SPST or SPDT dry contact closure rate is 0~6000 CPM (0~100 CPS). The SPST switch input mode utilizes a low pass filter and a Schmitt Trigger with 15% hysteresis for debouncing. The SPDT switch input mode which utilizes an R-S Flip-Flop for debouncing can accept high speed dry contact closure rates of 0~600,000 CPM (0~10,000 CPS) if the low pass filter is reduced or eliminated. The PC-45XAC also accepts 3-30VDC positive going pulses or AC signal inputs up to 15MHz. A 500mV hysteresis aids the accurate counting of slow changing waveforms.
Other features include logic controls such as inhibit, reset, display hold, carry output, overrange output, and outputs to continuously trickle charge an external user supplied Ni-Cad battery back up which will prevent loss of data in case of intermittent or power-out situations. There are 4 programmable decimal points, and unlimited cascading to achieve multiples of four digits using 2 or more PC-45XAC units. In this type of operation only the left most meter will display a fifth digit.
The display hold feature enables the user to latch the display while the counter continues counting.
Without affecting the latched display, the counter may be reset to zero by the reset control or the counting function may be stopped and started by the inhibit control. When the Display Hold is released, the data present in the counter at that time is instantly displayed.
With external logic control, the PC-45XAC may be used as a frequency counter, RPM indicator or period counter. The large 0.48" LCD display has excellent readability in both high and low ambient light conditions, and its low power consumption 120VAC-1 W or 5VDC-2mW makes it especially useful in remote locations.
SPECIFICATIONS
COUNT INPUTS
SPST Contact Closure:
SPDT Contact Closure:
3-30V AC or DC Pulse:
0~6000 CPM (100Hz) with 500Hz Low Pass filter and Schmitt Trigger set at 15% Hysteresis
0~6000 CPM (100Hz) with 500Hz Low Pass filter and R-S Flip-Flop. 0~600,000 CPM
(10kHz) with filter removed 0~500KHz with Schmitt Trigger threshold of 2V and 500mV Hysteresis. If the internal 100k overvoltage protection resistor is removed the max count is 0~15MHz
Open Collector Sensing: All inputs are compatible with open collector sensing devices
Over Voltage Protection: Pins 6, E & F are protected up to 100V peak
overload with internal 100k resistors.
Caution: All other input or control pins are NOT PROTECTED against High Voltage
CONTROLS & OUTPUTS
Reset:
Inhibit Count:
Display Hold:
Carry Output:
Overrange Output:
Display:
Decimal:
Overload Indications:
Back-Up Battery:
Power Requirements:
Dry Switch closure to ground or Logic Low "0" input for min. 3S resets counter to zero. (50A pull-up current is provided).
Dry Switch closure to ground or Logic Low "0" input will prevent the D flip-flop on the count input from operating (10A pull-up current is provided)
An Open input or Logic High "1" input on this pin "freezes" the display while the counter continues to operate independently. A Dry Switch closure to ground or Logic low "0" input for min. 3S updates the display (10A pull up current is provided.) For continuous display of the counter input the display hold function should be connected to ground Internal solder pad SP2 provides a logic signal output that occurs each 10,000 counts for cascading the count in 4 digit mutilples Internal solder pad SP1 goes to Logic High "1" when the count exceeds 20,000 counts 0.48" LCD Max. 19999 User programmable to 4 positons All digits blank except decimal points 1.8mA output is provided to trickle charge a user supplied 7.2V Ni-Cad battery (Everyready CH22 or equivalent)
110VAC or 220VAC. 5% at 50Hz; 117V or 230VAC. 5% at 60Hz and 400Hz or regulated 4VDC to 6VDC at 400A or unregulated 7V to 16VDC at 1mA to 3mA. -20 C to +60 C
Operating Temperature:
PC-45XAC (E-3)
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CONNECTOR PINOUTS
The Texmate Model PC-45XAC interconnects by means of a standard PC board edge connector having two rows of 10 pins, spaced on 0.156" centers. Connectors are available from Texmate, or from almost any connector manufacturer.
FUNCTIONAL DIAGRAM
The diagram below depicts the Model PC-45X in its standard 2V F.S. form with all component values indicated for this mode of operation. Variations from the standard for use in special applications will be found under the heading Typical Application Circuits & Connection Instructions.
REAR VIEW OF METER CASE
Pin A - Back Plane input/Display Test: Pin A is connected to the display's back plane which forms the common base of the LCD capacitance structure. Join Pin A to Back Plane Output Pin 1 for normal operation.
For Display Test connect Pin A instead to System Ground Pin J and all operative segments will turn on. CAUTION: The Display Test function is only intended for momentary operation. Continuous application of Display Test will, in time, damage the display. SEE PAGES 5 & 6 FOR A DETAILED EXPLANATION OF LCD OPERATION.
Pin B, C, D AND 3 - Decimal Select: Decimal point may be displayed as required by connecting the appropriate pin to Decimal Select Common Pin
2. Any number of decimal points can be turned on at the same time. An open circuit will turn off the decimal points. However, static current pickup and/or PCB leakage of more than 100nA can cause decimal points to turn on undesirably. Therefore, it is recommended that the unused decimal points be connected to Back Plane Output Pin 1 either directly or by a resistor of less than 5M to insure an off condition. Caution: Any DC component introduced to the display drive circuitry can, in time, cause permanent damage, PLEASE READ PAGE 5 & 6 FOR DETAILED EXPLANATION OF LCD OPERATION.
Pin E - SPDT Switch Input Enable: To use Pine E, J10 must be opened.
This creates an R-S Flip Flop for failsafe switch closure counting. After an input is received on Pin F, no further count inputs will be accepted until Pin E is enabled by a contact to System Ground Pin J. When using a SPDT switch, connect the normally closed terminal to Pin E, the normally open terminal to Pin F, and the common terminal to System Ground Pin J. A low pass filter is provided to reject high frequency noise for operation within the range of 0~6000 CPM (100Hz). For high speed contact closure operation, up to 10,000 counts per second max., C3 and C4 must each be reduced to 100pF or removed entirely.
Pin F - SPST/SPDT Switch Input: Connect a dry contact switch between Pin F and System Ground Pin J for a count on contact closure rate of 0~6000 CPM (100Hz). Contact debouncing is provided by a low pass filter and a Schmitt Trigger factory set with a 15% Hysteresis. This standard contact closure input mode of operation is designed for up to 100 Counts per second or 6000 CPM. Faster counting rates can be implemented by proportionally reducing the low pass filters time constant: for example, 0~200 counts per second can be counted if C3 is changed ot 5000pF. For High Speed contact closure operation, a SPDT switch must be used (see Pin E).
Pin H - Display Hold: Pin H controls a latch between the display driver circuit and the counter circuit. For normal continuous display of the count function Pin H must be connected to System Ground Pin J or have Logic Low "0" applied. If Pin H is left open (a 10A pull-up current is provided), or if Logic High "1" is applied, the display register will latch up and hold the count displayed. The counter section will continue independent operation and
PC-45XAC (E-3)
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aSchmitt Trigger with a 2.0V threshold and 0.5V of hysteresis. A 100k pull-up resistor R6 and a 100k overvoltage protection resistor R7 are also incorporated into the circuit. The count occurs on the negative going edge of a positive input signal. Logic Low "0" = 0 to 1.5V. Logic High "1" = 2.5 to +30V. The 100k overvoltage protection resistor R7 will protect the counter from overvoltages up to a peak of 100V.
Caution: See Pin J for precautions necessary to avoid damage to the counter from externally generated signals. The overvoltage protection resistor limits the maximum count speed to 0~500KHz. If the input signal is limited externally to 0~+5VDC Logic Levels and the overvoltage protection resistor is replaced with a jumper, the counter can typically operate up to 15MHz.
Pin 7 - Reset Input: For normal acumulative counting Pin 7 is left open or applied to Logic High "1" (50A pull-up current is provided).
When Pin 7 is connected to System Ground Pin J or has Logic Low "0" applied the counter will reset to zero.
Pin 8 - +5VDC System Power Output: Pin 8 provides an auxiliary output of +5VDC referred to System Ground for external use up to 5mA maximum. Caution: Pin 8 is not overload protected and care should be exercise to avoid damage to the counters power supply. Although the PC-45XAC is designed for AC power operation it is possible to operate the unit from a +4VCD to +6VDC source, in which case the positive input should be connected to Pin 8 and the power ground connected to System Ground Pin J.
Pin 9 - No Connection: No circuit connections are made on Pin 9.
Pin 10 - AC Power Input (Active): Connect the active side of the AC power input to Pin 10 (Please also see Pin K.) Provision has been made on the PC board for an optional user added pico fuse if an internal fuse is used, J13 must be opened.
COMPONENT SIDE
SOLDER SIDE
COUNT INPUT WITH SINGLE CONTACT SWITCH CLOSURE
DOUBLE CONTACT CLOSURE COUNT INPUT
A mechanically coupled single pole single throw contact closure can be used as a count inptu device for count rates up to 6000CPM (100Hz).
The contact noise debouncing circuit consists of a low-pass filter and a Schmitt Trigger with 15% Hysteresis. If required, a higher count rate of 0~400Hz can be achieved by reducing C3 to 2500pF.
A mechanically coupled single pole double throw contact closure can be used as a count input device when J10 is opened. The contact noise debouncing circuit consists of a low-pass filter and an R-S Flip-Flop. After a count input is created by making the connection between Pin F and Pin J, no further count inputs will be accepted until a contact is made between Pin E and Pin J. For higher count rates up to 0~600,000CPM (10KHz) reduce C3 and C4 to 2500pF or remove entirely.
PC-45XAC (E-3)
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3-30 AC/DC PULSE INPUT AND HIGH FREQUENCY +5VDC LOGIC LEVEL INPUT
The input circuit incorporates a Schmitt Trigger with a 2.0V threshold and 0.5 V of hysteresis. The count occurs on the negative going edge of an input signal. R6 acts as a pull-up resistor. R7 provides overvoltage protection to a peak of 100V. For 0~15MHz operation from externally limited +5VDC logic level signals, replace R7 with a jumper.
OFFSET AC-SIGNAL INPUT MODE An Isolation Capacitor C, is installed externally to isolate the offset votage. The meter is then AC coupled so that the counter can be employed to measure an AC signal that is carried on an offset DC voltage.
OPTO-ELECTRIC COUNT INPUT
A solid-state opto-electric NPN device can be interfaced directly to the event counter. External power may be required to power the LED seciton ofthe device if more than 5mA is required. Note: R1 can be changed to match the sensitivity of the photosensor.
MOST COUNT OUTPUT DEVICES CAN BE DIRECTLY INTERFACED
Photoelectric devices, contact closure, switches, NPN open collector transistors, and voltage pulses up to 100V can be used directly with Model PC-45XAC without expensive and complicated interfacing circuitry.
CASCADING THE UNIT
Open J5 and J8 and close J9 to disable overange indication feature.
Open J4 and jumper solder pads E & D to disable the MSD 1's to convert the first counter to a meter 9999 count mode. Join SP2 of the first counter to Pin 6 of the cascading counter to provide a total of 19999~9999 counts maximum.
PC-45XAC (E-3)
EXTERNAL LOGIC CONTROL PERMITS OPERATION AS A PERIOD COUNTER OR REQUENCY/RPM METER
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INTRODUCITON TO FIELD-EFFECT LIQUID CRYSTAL DISPLAYS
The field-effect liquid crystal display is the most advanced and reliable liquid crystal display available today. Its operation depends on changing the optical properties of the liquid crystal by applying an electric field. The effect of this change is in turn, made visible by polarizers placed on each side of the display cell.
ELECTRICAL CHARACTERISTICS - Electrically, liquid crystal displays function like capacitors and, unlike LED's, are driven with an AC signal. This AC signal is necessary to maintain the electric field required to rotate the liquid crystal molecules. The LCD drive circuitry used for Texmate displays puts out a 60Hz square wave signal which is truly symmetrical and contains no DC components. Fig. 3 shows the typical AC drive signal's relationship between the common back plane and the individual segment elements. A segment is turned on when its drive signal is 180 out of phase with respect to the back plane. A segment is turned off when its drive signal is in phase with the back plane so that there is no net voltage between the back plane and the segment. Fig. 4 explains operation of he internal logic circuitry used to create the AC drive signal described in Fig. 3.
FIGURE 1. LCD Cross-Section
Liquid crystal displays are inherently reliable and thousands of Texmate's proprietary, customized LCD displays have been in continuous use throughout the world often in harsh environmental conditions for many years. An understanding of the simple precautions outlined here will provide many years of reliable maintenance-free use.
DISPLAY CONSTRUCTION AND OPERATION - The best description of liquid crystal is that is an ordered fluid of a class called nematic. Nematic fluids of the type used for liquid crystal displays consist of cigar-shaped organic molecules with the long axis of each molecule pointing in the same direction. The display cell is constructed from two pieces of glass coated on the inner side with transparent indium oxide conductors, as shown in Fig.1. Each of the transparent conductors on the inside of the larger rear glass piece is shaped to form the individual segments of the display and are terminiated on individual contact pads. The single conductor on the inside of the front glass piece is shaped so as to be common to all the segments on the rear glass. Traditionally this common conductor is usually referred to as the "back plane". The common back plane is connected to the two left most (viewed from the front) contact pads by a small dot of conductive epoxy imbedded in the spacer/seal. The glass surfaces are also specially treated to align the liquid crystal molecules in a partiular direction. Alignment is parallel to the plane of the glass, with the alignment direction of the top rotated 90 relative to the alignment of the bottom plate. This causes the cigar-shaped liquid crystal molecules in the cell to assume a twisted orientation, when viewed from top to bottom. As shown in Fig. 2, the plane of polarization of polarized light will follow this twist and emerge from the cell rotated 90. Thus, when the cell is placed between crossed polarizers, the polarizers will transmit light. When an electric field is applied to the transparent conductors on the inside of the glass cell, the liquid crystal molecules will physically move and reorient themselves parallel to the field.
The 90 twist is then destroyed, and that portion of the cell between the conductors will appear dark. Conversely, when the cell is placed between parallel polarizers light cannot be transmitted and the entire display will appear dark. When the electric field is then applied the segments formed by the transparent conductors will then appear light against a dark ground.
FIGURE 2. LCD Operating Pinciples
FIGURE 3. Typical AC Drive Signals
FIGURE 4. Exclusive-Or Drive Circuit
CAUTION - If a DC component is introduced into the display, electrolysis occurs and the transparent conductors which form the individual display elements will, in time, be destroyed. A DC component can be created by leakage or inadvertent connection to system ground of unused display elements such as decriptors and decimal points. For this reason it is recommended that unused display elements be connected to to the back plane output drive pin which is provided on all Texmate LCD meters. The back plane signal will then drive these unused elements to an off condition.
Short term application of a DC signal will not damage the display and, in fact, the display test function in most Texmate meters utilizes a DC signal to light up all segments for test purposes. This function, however, is only intended for momentary usage and if left activated for longer than 24 hours, damage to the display will occur.
PC-45XAC (E-3)
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HUMIDITY SPECIFICATIONS - The polarized film used in LCD displays can be damaged by combinations of high temperature and high humidity, i.e., 85% RH at 50 C for 96 hours. Although these extreme conditions are rarely encountered in actual use.
Texmate has provided for easy removal and replacement of polarizers and reflectors (see Fig. 5). The front polarizer is a loose piece and the combination rear polarizer and reflector can be slid out from the space between the LCD and the PC board.
Spare replacement polarizers are available from Texmate. The polarizers normally provided with the meter as standard provide a reflective display mode. That is the background appears white and the segments appear black. Substitute rear polarizer/ reflectors can be ordered with the opposite polarization plane.
This will cause the display to become transmissive, with a black foreground and white segments. The polarization plane of the front polarizer is never changed from horizontal because although to the naked eye the display would operate perfectly if it were changed, a person viewing the display through polarized sunglasses would be unable to read any segments as the entire display would appear black.
FIGURE 5. Replaceable Polarizers & Reflector Assembly
PANEL CUTOUT
FRONT VIEW
SIDE VIEW
TOP VIEW
option metal
screw mounting clip
When extra panel mounting tightness is required, optional Screw Mounting Clips can be purchased seperately and attach to the sliding mounting side clips
1934 Kellogg Ave., Carlsbad, CA 92008 Tel: 1-760-598-9899 1-800-TEXMATE Email: [email protected]
PC-45XAC (E-3)
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Texmate is an American manufacturer of high durability industrial grade panel meters, bar graphs, and transducers. Texmate's meters are frequently equipped with relays and various signal outputs for industrial automation applications and are known for their extremely long service life.