Introduction: HOME I/O- PLC Interfacing
PLC Interfacing- Digital Control of Home I/O using PLC – Allen Bradley
Starting Conditions: Home I/O is being controlled by Inbuilt Sensors I/O Signals
- Entrance gate Closed (Bit 261)
- Entrance gate Opened (Bit 260)
- Entrance gate Open (Bit 193)
- Entrance Gate Closed (Bit 194)
Connect I/O Functions to be used
Note: This activity is extended to the Activity 1 in which we controlled the Gate Latching/Unlatching via Connect I/O Logic. Here we are going to perform the similar operation using PLC Ladder Logic
Step 1: Wiring Diagram With USB 4704 DAQ Card I/O Solutions:
PLC Input Wiring:
We have connected Input IN8 & IN9 to Digital Output DO0 & DO1 respectively. The Common of PLC Input is connected to the Digital Ground of DAQ Card.
PLC Output Wiring:
PLC Output OUT 0 & OUT 1 is connected to Digital Input DI0 & DI1 of DAQ Card. Whereas the Common of PLC output is connected to Digital Ground of Input terminals of DAQ Card.
Step 2: Connect I/O Interface Connection
To read/write the values in PLC, we have made the following connection in Connect I/O Software.
Step 3: Description of the Functions Used:
Source Bit: This is an ON/OFF bit used to give TRUE/FALSE Signal to Logical gates. When you press it once, it goes to TRUE & when you press is again it goes to FALSE
Bit 193: Entrance Gate (Open): This is the standardized bit used to open the Entrance gate
BIT 260: Entrance gate (Opened): This bit gives feedback for the Gate 1. When Gate 1 is fully opened, it gets ON else its OFF.
Bit 194: Entrance Gate (Close): This is the standardized bit used to close the Entrance gate
BIT 261: Entrance gate (Closed): This bit gives feedback for the Gate 1. When Gate 1 is fully closed, it gets ON else its OFF.
Step 4: Explanation of Solutions:
PLC INTERFACING- Digital Control of Home I/O using PLC –Allen Bradley
In this ladder Logic we have used Latch/ Unlatch commands to make the logic little easy to follow.
Following is the brief explanation of the ladders:
- In Ladder 0000: The Internal Bit B3:0/0 is used to Latch the Output O:0/0.
- In Ladder 0001: Input I:0/9 is used to Unlatch the Output O:0/0
- In Ladder 0002: The Internal Bit B3:0/1 is used to Latch the Output O:0/1.
- In Ladder 0003: Input I:0/8 is used to Unlatch the Output O:0/1
This logic has been made in Rs Logix 500- PLC Programming Software for Allen Bradley.
Step 5: To Latch/Unlatch the Gate in Home Using PLC Logics
Step 1: Latching the Opening of Door using Rising Edge of Sensor 1
We have used internal bit of PLC B3:0/0 for illustration purpose to latch the PLC Output O:0/0. As discussed above, this Output is connected to DAQ Input IDI0.
Hence, it latches the Gate Open Bit 193 & opens the door.
Step 6: Unlatching the Output Bit When Door Is Fully Opened.
Here, when the gate is fully opened, we get the True condition of Entrance Gate Opened Bit -260 which is connected to IDO1 of DAQ Card.
Hence, PLC Input I:0/9 which respond to the Entrance Gate Opened Bit-260 connected at IDO1 unlatches the O:0./0 which further Turns OFF the Entrance Gate Open Bit 193 & stops opening of gate.
Step 7: Latching the Close Operation Using Infrared 2
Here, We have used internal bit of PLC B3:0/1 to latch the PLC Output O:0/1. As discussed above, this Output is connected to DAQ Input IDI0.
Hence, it latches the Gate Open Bit 194 & closes the door.
Step 8: Unlatching the Output Bit Using Gate Closed Bit
Similar to step 2, when the gate is fully closed, we get the True condition of Entrance Gate Closed Bit -261 which is connected to IDO0 of DAQ Card.
Hence, PLC Input I:0/8 which respond to the Entrance Gate Closed Bit-261 connected at IDO0 unlatches the O:0./1 which further Turns OFF the Entrance Gate Close Bit 194 & stops closing of gate.
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