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ECT 464

ECT 464. Lecture 7 Timers. Sorrow looks back. Worry looks around. Faith looks up. Let us fix our eyes on Jesus, the author and perfecter of our faith, who for the joy set before him endured the cross, scorning its shame, and sat down at the right hand of the throne of God. Hebrews 12:2.

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ECT 464

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  1. ECT 464 Lecture 7 Timers

  2. Sorrow looks back. Worry looks around.Faith looks up. Let us fix our eyes on Jesus, the author and perfecter of our faith, who for the joy set before him endured the cross, scorning its shame, and sat down at the right hand of the throne of God. Hebrews 12:2

  3. Timer Data File Elements • EN – timer enabled • TT – timer timing • DN – done bit • PRE – Preset value word • ACC – Accumulated value word

  4. Word values • Accumulator Value – Number of clock cycles that have occurred since the timer was enabled. • Preset Value – Value which the timer must count up to until the PLC sets the done bit. • Values between 0 and 32,767

  5. Time Base • The timers have a time base by which they are clocked. • Valid Time Bases are: • 1 second • 0.1 seconds • 0.01 seconds

  6. Address Structure • The Timer uses the typical element addressing scheme. • Examples: • T4:0.ACC • T11:33/DN • T4:2/TT • T12:4/EN • T15:56.1/0 = T15:56.PRE/0 • T16:29.2/15 = T16:29.ACC/15

  7. Timer On Delay (TON) • Enable – Set whenever the input rung is true • Timer Timing – Set when enable is true and accumulated value is less than the preset value. • Done – Set when the enable is true and the accumulated value is greater than or equal to the preset value.

  8. Timer Off Delay (TOF) • Enable – Set whenever the input rung is true • Timer Timing – Set when enable goes false and accumulated value is less than the preset value. • Done – Set when the enable or timer timing bit is true.

  9. Retentive Timer (RTO) • Enable – Set whenever the input rung is true • Timer Timing – Set when enable goes true and accumulated value is less than the preset value. • Done – Set when the enable is true and the accumulated value is greater than or equal to the preset value. Does not reset accumulated value when enable is false.

  10. Timer Uses • Use to count time • Extend push button inputs • Delay inputs • Assembly line product control

  11. Timer Examples • On Delay: Output B comes on at a specific set time after output A is turned on. When A is turned off, B goes off. • Off Delay: Both A and B have been turned on at the same time. Both are in operation. When A is turned off, B remains on for a specific set time period before going off. • Limited On Time: A and B go on at the same time. B goes off after specific set time period, but A remains on. • Repeat Cycling: An output pulses on and quickly off at a constant preset time interval. • One-Shot Operation: Output B goes on for a specified time after output A is turned on. Output B will run for its specified time interval even if A is turned off during the B timing interval.

  12. Timer Examples • Alternate on and off of two outputs: Two alternately flashing lights. The time for the two lights could be different. • Multiple On Delay: Two different events start at different time intervals after an initial starting time reference point. • Multiple Off Delay: Two different functions remain on for two different time intervals after a process is turned off. • Interval time within a cycle: We may require that an output come on 7.5 seconds after system start up, remain on for 4.5 seconds, and then go off and stay off.

  13. Timer Example 1 On Delay: Output B comes on at a specific set time after output A is turned on. When A is turned off, B goes off.

  14. Timer Example 2 Off Delay: Both A and B have been turned on at the same time. Both are in operation. When A is turned off, B remains on for a specific set time period before going off.

  15. Timer Example 3 Limited On Time: A and B go on at the same time. B goes off after specific set time period, but A remains on.

  16. Timer Example 4 Repeat Cycling: An output pulses on and quickly off at a constant preset time interval.

  17. Timer Example 5 One-Shot Operation: Output B goes on for a specified time after output A is turned on. Output B will run for its specified time interval even if A is turned off during the B timing interval.

  18. Timer Example 6 Alternate on and off of two outputs: Two alternately flashing lights. The time for the two lights could be different.

  19. Timer Example 7 Multiple On Delay: Two different events start at different time intervals after an initial starting time reference point.

  20. Timer Example 8 Multiple Off Delay: Two different functions remain on for two different time intervals after a process is turned off.

  21. Timer Example 9 Interval time within a cycle: We may require that an output come on 7.5 seconds after system start up, remain on for 4.5 seconds, and then go off and stay off.

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