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Ladder program elements to deal with active high and/or active low input devices

Ladder program elements to deal with active high and/or active low input devices.

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Ladder program elements to deal with active high and/or active low input devices

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  1. Ladder program elements to deal with active high and/or active low input devices This presentation is partially animated. Only use the control panel at the bottom of screen to review what you have seen. When using your mouse, make sure you click only when it is within the light blue frame that surrounds each slide.

  2. Integrating the field devices with a programmable controller and then creating the program that operates the field devices is a critical task. Input Modules Output Modules WBT-4 24 volts 120 volts 120 volts 48 volts I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers Simple Programmable Controller that has two input modules and two output modules Note the different voltage rating for the modules. Other modules with different voltage rating are available.

  3. To FCE motor Input Modules Output Modules Motor Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” N.O. Programmable Controllers N.O. Simple Programmable Controller that has two input modules and two output modules Input devices Output device Note the different voltage rating for the modules. Other modules with different voltage rating are available.

  4. To FCE motor Input Modules Output Modules Motor TSH Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers N.O. The challenge is not in attaching the wires to an assigned address (terminal) at the appropriate module. If this were a Temperature Sense High alarm device would it have an active high or active low output? Input devices 24 volts (active low) Output device N.O. The important thing is to know if the devices are wired to be active high or active low so you can pick the proper programming element for your ladder program.

  5. To FCE motor Input Modules Output Modules Motor Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers The challenge is not in attaching the wires to an assigned address (terminal) at the appropriate module. If this were a Temperature Sense High alarm device would it have an active high or active low output? Output device 120 volts N.O. What about this Start push button?

  6. To FCE motor Input Modules Output Modules Motor Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. The challenge is not in attaching the wires to an assigned address (terminal) at the appropriate module. Output device 120 volts N.O. (active low)

  7. To FCE motor Input Modules Output Modules Motor Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. The challenge is not in attaching the wires to an assigned address (terminal) at the appropriate module. Output device 120 volts N.O. (active low) Now lets attach the output device

  8. To FCE motor Input Modules Output Modules Motor Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. The challenge is not in attaching the wires to an assigned address (terminal) at the appropriate module. Output device 120 volts N.O. (active low) Now lets attach the output device

  9. I-1,3 I-0,0 O-0,1 To FCE motor TSH Start P.B. Input Modules Output Modules Motor O-0,1 Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. Rule of Thumb for programmable logic controllers Ladder Program “When the computer inside a programmable logic controller senses that an input address is at “logic 1” the computer changes the symbol you put into your program and then executes the ladder program rung.” Output device 120 volts Next, we write a ladder program to control this motor. N.O. (active low)

  10. I-1,3 I-0,0 O-0,1 To FCE motor TSH Start P.B. Input Modules Output Modules Motor O-0,1 Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. If the input device attached at input address I-0,0 is passive, Ladder Program (a) Will the programmable control change the symbol that is associated with input address I-0,0 ? YES ! Output device 120 volts N.O. “When the computer inside a programmable logic controller senses that an input address is at “logic 1” the computer changes the symbol you put into your program and then executes the ladder program rung.” (active low)

  11. I-1,3 I-0,0 O-0,1 To FCE motor TSH Start P.B. Input Modules Output Modules Motor O-0,1 Starter WBT-4 24 volts 120 volts 120 volts 48 volts 120 volts 24 volts (active low) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers Start P.B. If the input device attached at input address I-1,3 is passive, Ladder Program (a) Will the programmable control change the symbol that is associated with input address I-1,3 ? YES ! Output device 120 volts N.O. “When the computer inside a programmable logic controller senses that an input address is at “logic 1” the computer changes the symbol you put into your program and then executes the ladder program rung.” (active low)

  12. TSH N.O. Start P.B. Notice how this wiring of the temperature alarm input device is different than the previous example. To motor and FCE 24 volts 120 volts 120 volts motor Starter 120 volts 48 volts (active high) WBT-4 I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers 24 volts 120 volts N.O. (active low)

  13. I-1,3 I-1,3 I-0,0 I-0,0 O-0,1 O-0,1 TSH TSH Start P.B. Start P.B. TSH O-0,1 O-0,1 TSH N.O. Start P.B. You put this symbol into your program so the computer can change it to the other symbol when the terminal I-0,0 changes from logic “0” to logic “1”. Old New To motor and FCE 24 volts 120 volts 120 volts motor Starter 120 volts 48 volts (active high) WBT-4 I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers 24 volts 120 volts Notice how the program symbol for the TSH is also different as well. N.O. (active low) Program for previous active low wired temperature sense high alarm device.

  14. I-1,3 I-0,0 O-0,1 TSH Start P.B. O-0,1 To motor and FCE 120 volts Start P.B. 48 volts 24 volts 120 volts motor Starter Ladder Program 24 volts WBT-4 (active low) I-1,3 I-0,0 O-0,1 I-0,3 I-1,3 O-0,3 O-1,3 TSH N.O. “We-build-them” TSH Start P.B. 120 volts Programmable Controllers N.O. O-0,1 Start P.B. (active low) To motor and FCE 120 volts 48 volts 24 volts 120 volts motor Starter WBT-4 (active high) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers 120 volts 24 volts Notice how the wiring of the TSH input devices are different. N.O. Notice how the program elements are different as well. (active low)

  15. Ladder Program I-1,3 I-0,0 O-0,1 To motor and FCE Start P.B. TSH O-0,1 motor Starter 120 volts 120 volts 48 volts 120 volts 24 volts WBT-4 TSH N.O. I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers (active high) 24 volts 120 volts Study this example and write the program before you go on. N.C. (active high) Start P.B.

  16. I-1,3 I-0,0 O-0,1 TSH To motor and FCE Start P.B. O-0,1 motor Starter 120 volts 120 volts 48 volts 120 volts 24 volts WBT-4 TSH N.O. I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers Ladder Program (active high) 24 volts Now try this one. N.C. (active low) 120 volts Start P.B.

  17. To motor and FCE motor Starter WBT-4 (active high) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers 24 volts 120 volts N.C. (active high) Start P.B. To motor and FCE motor Starter WBT-4 (active high) I-0,3 I-1,3 O-0,3 O-1,3 TSH “We-build-them” N.O. Programmable Controllers 24 volts N.C. (active low) Start P.B. 120 volts Notice the difference.

  18. Ladder Program (active high) I-1,3 Ladder Program I-0,0 O-0,1 TSH N.O. I-1,3 I-0,0 O-0,1 24 volts Start P.B. TSH Start P.B. TSH N.C. O-0,1 (active low) O-0,1 120 volts Start P.B. (active high) TSH N.O. 24 volts 120 volts N.C. (active high) Start P.B. Notice the difference.

  19. Ladder Program I-1,3 I-0,0 O-0,1 Start P.B. TSH O-0,1 TSH N.C. Self assessment tool Write the program for this input device configuration. To motor and FCE motor Starter 120 volts 120 volts 48 volts 120 volts 24 volts WBT-4 (active Low) I-0,3 I-1,3 O-0,3 O-1,3 “We-build-them” Programmable Controllers 24 volts Check your answer, if it doesn’t agree run this presentation again. N.C. (active high) 120 volts Start P.B.

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