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Product Data Wire Fault (1527V DC) Input Module AllenBradley Wire Fault 1527V DC Input Module (Cat. No. 1771-DW) Product Data Description The Wire Fault (15-27V DC) Input Module converts seven on/off DC inputs to logic level signals compatible with Allen-Bradley programmable controllers that use the 1771 I/O structure. The module also detects if any wire in the circuit connecting the input device to the module or to the power supply has either: short circuited to ground open circuited You must connect a shunt resistor across the terminals of the input device to allow the module to monitor the wire condition for a fault. Seven shunt resistors, one for each input, are supplied with your module. 1 Product Data Wire Fault (1527V DC) Input Module Input Devices Typical 2-wire (hard contact) input devices compatible with the module include: DC pushbutton, limit, float, and selector switches The off-state leakage current of your 2-wire input devices should not exceed 1mA. Input Indicators Seven status indicators are located on the front of the module. These indicators show the status of inputs or the presence of a wire fault (figure 1). The indicator is on when contacts are closed, off when contacts are open, or flashing when the module detects that a wire in the input circuit has faulted. Input Indicators Figure 1 Wire Fault Status Indicators Reset Switch 2 A pushbutton reset switch is located below the last input indicator. Use the switch to manually reset the module after you have corrected a wire fault detected by the module. Press the switch using a narrow object such as a ball point pen. Product Data Wire Fault (1527V DC) Input Module Module Operation You program the module to report contact status or wire status. The sequences for monitoring and reporting contact status (figure 2, upper path) or wire status (figure 2 lower path) are described as follows. Figure 2 Wire Fault Module Block Diagram Module alternately monitors contact status: Contacts close. Opto-electrical isolator protects logic signals by isolating logic circuits from input wiring. Input filter removes false signals due to contact bounce or electrical interference. Input indicator turns on or off to show status of input contacts. Logic circuits process and store signals representing contact status. Module alternately monitors wire status: Input wire faults. Opto-electrical isolator protects logic signals by isolating logic circuits from input wiring. Module detects short circuited or open circuited wire by detecting a change in line monitoring current. Module latches faulted wire condition, if one exists. Module flashes the indicator for that input. Logic circuits process and store signals representing wire status. Module reports contact or wire status: Module detects that your program set or reset the request bit. 3 Product Data Wire Fault (1527V DC) Input Module Module reports corresponding contact or wire status to I/O adapter (if a remote I/O system) or to PC processor. PC processor and/or I/O scanner (if a remote I/O system) read(s) corresponding contact or wire status and returned status bit into the processor data table. After corrective action is taken for a wire fault condition, your program (or reset switch) resets the latched condition in the module. Line Monitoring The module provides a 6mA monitoring current through the shunt resistor for each input wire when input contacts are open, and a 20mA current when contacts are closed and the input wiring is good. A shorted or opened circuit disrupts this current. Programming You program the wire fault module similar to standard discrete I/O modules with the following exceptions. (Block transfer is not used.) Contact/Line Status — Your module constantly monitors contact and wire status. Your ladder program selects which status is reads. We recommend that you toggle the request bit to alternately read contact or wire status, and use appropriate logic when your program detects a wire fault. Request Bit — The request bit tells the module to report either contact status (bit is set) or wire status (bit is reset). The request bit is bit 07 or 17 of the module’s output image table byte depending on whether the module is in the left slot (bit 07) or the right slot (bit 17) of the module group. When your ladder program sets the request bit, the module’s input image table byte reports contact status of the seven inputs. When your ladder program resets the request bit, the module’s input image table reports wire status of the seven inputs. The module is unable to determine if the wire fault is a short or open circuit. Status Bit — The status bit identifies whether the module is reporting contact status or wire status. The status bit confirms the function dictated by the request bit. The status bit is bit 07 or 17 of the module’s input image table byte depending on whether the module is in the left slot (bit 07) or in the right slot (bit 17) of the module group. 4 When Data Table Bits Are I/O Data Indicates Contacts Are Status Data Indicates Wires Are Set Reset Closed Open Faulted Good Product Data Wire Fault (1527V DC) Input Module For example, the module’s input image table byte for contact status (inputs 10 and 12 closed) and wire status (wires to inputs 11 and 15 faulted) would appear as follows: Bit Designation 07 06 05 04 03 02 01 00 17 16 15 14 13 12 11 10 Contact Status 1 0 0 0 0 1 0 1 Wire Status 0 0 1 0 0 0 1 0 Function status bit Data is contact status or wire status depending on status bit 07 or 17. If all bits of the wire status byte are set, then the power supply could have failed, or the field wiring arm could have been removed from the wire fault module. Module Reset — You must correct the cause after the 1771-DW module detects a wire fault. Moreover, bits in the input image table remain set until they are reset manually or by program reset. Manual reset Press the reset switch on the front panel Program reset Reset bit 00 or 10 (depending on module location) of the module’s output image table byte using program logic Use either method for resetting one or more wire faults that the module has detected, and for resetting the module at power-up. If you want to disable the pushbutton reset switch, change a configuration plug inside the module. Do this by removing covers, locating the (blue) configuration plug on the component side of the board behind the LED indicator assembly, and floating the plug on one pin. WARNING: Do not use the complementary address of this module for word manipulation, or any I/O module as the complement to this module. The reset bit (00 or 10) must be reserved for the reset function. If you use the complementary word address for an I/O module or for word manipulation, unpredictable operation could occur with possible damage to equipment and/or injury to personnel. 5 Product Data Wire Fault (1527V DC) Input Module Example Program — Examples of user program logic (figure 3) show methods for storing contact status and wire status, resetting the module, and conditioning the use of contact status according to the status of the input wires. The example program toggles the request bit on alternate scans so that the module constantly updates contact status and wire status. The program stores contact status and wire status in separate storage words. In this example, it stores contact status in word 250 and wire status in word 251. 6 Product Data Wire Fault (1527V DC) Input Module Figure 3 Example Programming 7 Product Data Wire Fault (1527V DC) Input Module Input Connections Connect your 2-wire input devices to the 1771-WA field wiring arm terminals 0 thru 6. Terminal 7 is not used. Connect the positive output from the power supply to each input device the negative output to the module’s DC common terminal, terminal B. Connect the appropriate shunt resistor across the terminals of each input device that the module monitors for a wire fault. All unused inputs must have a shunt resistor in line with the power supply’s positive terminal. Otherwise, the module reports a wire fault for an input not connected (figure 4). Figure 4 Input Connections Power Supply 8 You should maintain a constant input voltage between each of the module’s input terminals (0 thru 6) and common terminal (terminal B). Select a power supply voltage that produces 15V DC up to 27V DC between the input and common terminals of the module. Allow for a voltage drop in the wires to your input devices, especially if you choose a voltage at either end of this range. We recommend a nominal supply voltage of 24V DC. Using a power supply voltage other than 24V DC "5% will require that you select a different shunt resistor and provide your own for each input. Product Data Wire Fault (1527V DC) Input Module Shunt Resistor Use the 3.3k carbon film 1/2-watt resistors supplied with your module as shunt resistors if your power supply voltage is 24V DC. Connect a shunt resistor across the terminals of each input device that you want to monitor for a wire fault. WARNING: Connect the shunt resistor across the terminals of the input device, or as close to the input could be intermittent or not function. This situation could possibly cause damage to equipment and/or injury to personnel. If the power supply voltage is lower than 23V DC or greater than 25V DC, use a different shunt resistor. Select the value of the shunt resistor based on power supply voltage as follows: Power Supply Shunt Resistor 15V DC 18V DC 21V DC 24V DC 28V DC 1.8k ohms 2.2k ohms 2.7k ohms 3.3k ohms 3.9k ohms Use shunt resistors having a "5% tolerance. If your power supply voltage is other than those listed, calculate the value of the shunt resistor as follows: R = Power Supply Voltage – 800 0.006 Wire Resistance The wire resistance is the total resistance in the wires (figure 4) between: positive power supply terminal and input device input device and input terminal on the module module common and negative power supply terminal Calculate your wire resistance by multiplying the total length of wire in feet by the resistance per foot for the following wire sizes. Wire Size Ohms per Foot 10 12 14 16 18 0.000999 0.001588 0.002525 0.004016 0.006385 9 Product Data Wire Fault (1527V DC) Input Module Your wire fault module operates correctly if the wire resistance is less than the maximum allowable value. The maximum allowable wire resistance depends on the power supply voltage as follows: Power Supply Maximum Wire Resistance 15V DC 18V DC 21V DC 24V DC 28V DC 25 ohms 50 ohms 75 ohms 100 ohms 133 ohms WARNING: Your wire fault module will not operate correctly if the resistance in the wires to each input device exceeds the maximum allowable value. Intermittent operation could occur with possible damage to equipment and/or injury to personnel. If the resistance in the wires to each input device exceeds the maximum allowable value for a power supply voltage, either use a heavier gage wire (lower wire size), or raise the power supply voltage. Input Filtering and Circuit Protection Input filtering limits the effect of voltage transients caused by contact bounce and/or radiated electrical noise. If not filtered, voltage transients could produce false data. The delay due to input filtering is nominally 33"6ms for turning inputs on or off, or 3"2 ms for detecting a wire fault. Module logic and wire fault monitoring circuits are protected from possible damage due to electrical transients by 1500V opto-electrical isolation. The module’s inputs are protected from the application of reverse voltage up to 250V DC. CAUTION: Application of voltages above the maximum specified input voltage can damage module circuitry. Keying The module is keyed to guard against installation in the wrong module slot. To implement this protection, insert keying bands supplied with the I/O chassis into the upper backplane connector of the slot for this module in the following positions (figure 5): Between 2 and 4 Between 20 and 22 10 Product Data Wire Fault (1527V DC) Input Module Figure 5 Keying Bands Placement You can change the positions of keying bands if subsequent system design requires the insertion of a different type of I/O module in this slot. 11 Product Data Wire Fault (1527V DC) Input Module Specifications Inputs G 7 OptoElectrical Isolation (contact and line monitoring inputs) G 1500V DC Module Location inputs) G 1771 I/O chassis Backplane Current G 300mA max Input Voltage Range G 15 to 27V DC Environmental Conditions G Operating Temperature 0 to 60°C (32 to 1 40°F) G Storage Temperature -40 to 85°C (40 to 185° F) G Relative Humidity Nominal Input Current (closed contacts) G 20mA @ 24V DC typical Maximum OffState Current (@ 24V DC) G 1mA 5 to 95% (without condensation) Wiring Nominal Line Monitoring Current (@ 24V DC) G 6mA contacts open G 20mA contacts closed G Less than 4mA for detection of wire fault G 14 gauge stranded (max) G 3/64 inch insulation (max) Keying G Between 2 and 4 G Between 20 and 22 Input Impedance G 1k2k ohms (on state) G 2k3k ohms (off state) Input Signal Delay G 33"6ms for contact status G 3 " 2ms for wire fault status 1985 Allen-Bradley Company. PLC is a registered trademark of Allen-Bradley Company. With offices in major cities worldwide WORLD HEADQUARTERS Allen-Bradley 1201 South Second Street Milwaukee, WI 53204 USA Tel: (1) 414 382-2000 Telex: 43 11 016 FAX: (1) 414 382-4444 EUROPE/MIDDLE EAST/AFRICA HEADQUARTERS Allen-Bradley Europe B.V. Amsterdamseweg 15 1422 AC Uithoorn The Netherlands Tel: (31) 2975/43500 Telex: (844) 18042 FAX: (31) 2975/60222 Publication 1771-2.69 — February 1986 Supersedes Publication 1771-2.69 — February 1985 12 As a subsidiary of Rockwell International, one of the world’s largest technology companies — Allen-Bradley meets today’s challenges of industrial automation with over 85 years of practical plant-floor experience. More than 11,000 employees throughout the world design, manufacture and apply a wide range of control and automation products and supporting services to help our customers continuously improve quality, productivity and time to market. These products and services not only control individual machines but integrate the manufacturing process, while providing access to vital plant floor data that can be used to support decision-making throughout the enterprise. ASIA/PACIFIC HEADQUARTERS Allen-Bradley (Hong Kong) Limited Room 1006, Block B, Sea View Estate 28 Watson Road Hong Kong Tel: (852) 887-4788 Telex: (780) 64347 FAX: (852) 510-9436 CANADA HEADQUARTERS Allen-Bradley Canada Limited 135 Dundas Street Cambridge, Ontario N1R 5X1 Canada Tel: (1) 519 623-1810 FAX: (1) 519 623-8930 LATIN AMERICA HEADQUARTERS Allen-Bradley 1201 South Second Street Milwaukee, WI 53204 USA Tel: (1) 414 382-2000 Telex: 43 11 016 FAX: (1) 414 382-2400 PN 955099-41 Printed in USA