1 / 40

Timer Instructions for Efficient Automation Control

Learn how to use timer instructions efficiently in industrial automation control systems to manage processes and equipment. Understand TON, TOF, RTO categories and their applications. Master timer parts, ladder diagram operation, and troubleshoot worked-out problems.

dannyw
Download Presentation

Timer Instructions for Efficient Automation Control

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Timer Instructions Overview Instructions: Use the Page Up and Page Down keys to navigate through this presentation. When you are done viewing the presentation, close this window.

  2. Timers: Applications • Delay motors from starting at the same time when a switch is closed (TON Done bit) • Keep track of downtime – machine is up most of the time and down sometimes (RTO ACC bit) • Open a valve for a given time after a switch is closed (e.g.,10 seconds) • Measure the cycle time of a process (RTO ACC bit) Fall 2014 - S. Hsieh

  3. Examples • Keep track of total time required to make a batch of a product (RTO ACC bit) • Turn mixing motor off 2 minutes after the switch is closed (TON – Timing bit) • Hold clamp on for 25 seconds after glue is applied after a switch is closed then open (TOF – Timing bit) • Open a valve 27 seconds after a switch is turned close. If interrupted, the valve should close and the time be reset to 0. (TON – Timing bit) Fall 2014 - S. Hsieh

  4. Categories of Timer Instructions • TON (Timer on delay) Timer remains true for a preset time interval • TOF (Timer off delay) Timer remains false for a preset time interval • RTO (Retentive timer on delay) Timer remains on for a preset time interval

  5. Parts of a Timer Instruction • Word 0: Control word • Enable bit(.EN) -- is set when the rung is true • Timer Done Bit (.DN)-- changes state when accumulated value reaches a preset value • Timer Timing bit (.TT)-- is set while the timer is incrementing its accumulated value

  6. Parts of a Timer Instruction (cont.) • Word 1: Preset Value (.PRE) • the value the timer must reach before the controller sets the DN bit. When ACC = PRE, the DN bit is set. PRE can be used to control an output device. • Word 2: Accumulated Value (.ACC) • the time elapsed since the timer was last reset. When ACC is enabled, the timer updates it continually.

  7. Parameters to Enter • Accumulated value (.ACC) • Preset value (.PRE) • Time base - the duration of each time base unit Duration of timer = (preset value - accumulator value) * time base

  8. TON Instruction

  9. TON stands for... • TIMER DELAY ON • Time delay period is from the instant the rung goes TRUE until the DN bit is turned on

  10. TON can be used to... • Create a short pulse at the beginning of a longer input condition; • Delay the start of a function for a defined period of time from the start of some other function

  11. TON Ladder Diagram

  12. TON operation • When the rung goes TRUE, the EN and TT bits go on. • When the accumulated value (ACC) reaches the preset value (PRE), • TT bit goes off • EN bit stays on • DN bit turns on

  13. TON operation (cont.) • When the rung goes from TRUE to FALSE and the accumulated value (ACC) is less than the preset value (PRE) • EN and TT bits turn off • Accumulated value is reset to 000 • Timer reset instructions can be used to clear ACC

  14. TON EN bit • Is set when rung conditions are TRUE • Remains set until rung conditions go FALSE

  15. TON TT bit • Is set when • rung conditions are TRUE AND • ACC < PRE • Remains set until • rung conditions go FALSE

  16. TON DN bit • Is set when ACC = PRE • Remains set until rung conditions go FALSE

  17. Worked Out Problems • Turn on L1 if sw1 is closed for 12 seconds. • When sw1 is closed, turn on motors 10, 11, and 12. Turn off motors 10, 11, and 12 at five-second intervals when sw1 is opened.

  18. TOF Instruction

  19. TOF stands for... • TIMER DELAY OFF • Time delay period is from the instant the rung goes TRUE to FALSE until the DN bit is turned off

  20. TOF can be used to... • Create longer output functions derived from short input functions; • Generate a short pulse at the end of a long input function

  21. TOF Timer Instruction • TOF instruction begins to count time base intervals when the rung makes a true-to-false transition. • As long as rung conditions remain false, the timer increments its accumulated value (ACC) each scan until it reaches the preset value (PRE). • The controller resets the accumulated value when rung conditions go true regardless of whether the timer has timed out Sheng-Jen (“Tony”) Hsieh, Texas A&M University

  22. Using the TOF Status Bits • Where, the bit is set means set to 1 Sheng-Jen (“Tony”) Hsieh, Texas A&M University

  23. TOF Ladder Diagram

  24. TOF operation • When the rung goes TRUE, the EN and DN bits go on. • When the accumulated value (ACC) reaches the preset value (PRE), • DN bit goes off • AC is reset to 000

  25. TOF operation (cont.) • When the rung goes from TRUE to FALSE and the accumulated value (ACC) is less than the preset value (PRE) • DN bit stays on • Timer begins to accumulate time for the delay period • TT bit goes on and stays on for preset time, then resets • Timer reset instructions cannot be used to clear ACC

  26. TOF EN bit • Is set when rung conditions are TRUE • Remains set until rung conditions go FALSE

  27. TOF TT bit • Is set when • rung conditions are TRUE to FALSE AND • AC < PR • Remains set until • rung conditions go TRUE again

  28. TOF DN bit • Is set when rung conditions are TRUE • When rung conditions go from TRUE to FALSE and ACC < PRE • Remains set until • ACC = PRE

  29. RTO Instruction

  30. RTO stands for... • RETENTIVE TIMER DELAY ON • Similar to TON • Time delay period is from the instant the rung goes TRUE until the DN bit is turned on (like TON)

  31. RTO can be used for... • Maintenance functions; • Diagnostic programs

  32. RTO Timer Instruction • Use the RTO instruction to turn an output on or off after its timer has been on for a preset time interval. • The RTO instruction is a retentive instruction that lets the timer stop and start without resetting the accumulated value (ACC). Sheng-Jen (“Tony”) Hsieh, Texas A&M University

  33. Using the RTO Status Bits • To reset the ACC value and status bits, you must program a reset (RES) instruction with the same address Sheng-Jen (“Tony”) Hsieh, Texas A&M University

  34. Timer: RTO

  35. RTO operation • (Like TON) When the rung goes TRUE, the EN and TT bits go on. • (Like TON) When the accumulated value (ACC) reaches the preset value (PRE), • TT bit goes off • EN bit stays on • DN bit turns on

  36. RTO operation (cont.) • When the rung goes from TRUE to FALSE and the accumulated value (AC) is less than the preset value (PR) • EN and TT bits turn off • Accumulated value is NOT reset • Timer reset instructions must be used to clear AC

  37. RTO EN bit • (like TON) Is set when rung conditions are TRUE • (like TON) Remains set until rung conditions go FALSE

  38. RTO TT bit • (like TON) Is set when • rung conditions are TRUE AND • AC < PR • (like TON) Remains set until • rung conditions go FALSE OR • when the DN bit is set

  39. RTO DN bit • (like TON) Is set when AC => PR • Remains set until the appropriate RES instruction is enabled

  40. Close this window and then select items 4, 5, 6 TON, TOF, and RTO Simulation.

More Related