1. Timers

2. Mechanical Timing Relay Time delay relays are simply control relays with a time delay built in. Their purpose is to control an event based on time.

3. Timers On delay : With an on-delay timer, timing begins when coil is activated. When the time has expired, the contacts close/open(depends on the contacts normal condition) — and remain closed/opened until coil is de- activated. If coil is de-activated before time-out, the time delay resets On delay : With an on-delay timer, timing begins when coil is activated. When the time has expired, the contacts close/open(depends on the contacts normal condition) — and remain closed/opened until coil is de- activated. If coil is de-activated before time-out, the time delay resets Off delay : When using an off-delay timer, when coil is activated, the contacts close/open (depends on the contacts normal condition). De- activating the coil causes timing to begin. When the time has expired, the contact will return to their normal state. Off delay : When using an off-delay timer, when coil is activated, the contacts close/open (depends on the contacts normal condition). De- activating the coil causes timing to begin. When the time has expired, the contact will return to their normal state.

4. Normally-open, timed-closed Contact NOTC (normally open, timed close contact)- contact is open, when relay is de energized; when relay is energized, there is a time delay in closing.

5. Normally-open, timed-closed Example

6. normally closed, timed open contact NCTO (normally closed, timed open contact)-contact is closed when relay coil is de energized. When relay is energized, there is a time delay in opening.

7. normally closed, timed open example

8. Normally open, timed open contact NOTO (Normally open, timed open contacts)- contact is normally open, when relay coil is de energized when relay coil is energized contact closes instantly. When relay coil is de energized, there is a time delay before the contact opens.

9. Normally open, timed open contact example

10. normally closed, timed close contact NCTC (normally closed, timed close contact)- contact is normally closed when relay coil is de energized. When the relay coil is energized, contact open instantly. When the relay coil is de energized, there is a time delay before the contact closes.

11. normally closed, timed close contact example

12. Timer instructions PLC timers are output instruction that provides the same function as mechanical timing relay. ON delay provides the delay when the relay is energized. ON delay provides the delay when the relay is energized. OFF delay provides the delay when the relay is de energized. OFF delay provides the delay when the relay is de energized. Retentive Timer is similar to on delay timer except for the fact that the Accumulated value is retained even if the relay is de energized. Retentive Timer is similar to on delay timer except for the fact that the Accumulated value is retained even if the relay is de energized.

13. On delay timer example

15. off delay timer example

16. On delay timer example

17. Timer instructions SLC 500 CompacLogix

18. Timer instruction Address: By default, SLC 500 uses file #4 for timers. Compactlogix uses tags. Address: By default, SLC 500 uses file #4 for timers. Compactlogix uses tags. Time Base: SLC 500 uses 1.0s, 0.01s, 0.001s. CompactLogix uses only.001s Time Base: SLC 500 uses 1.0s, 0.01s, 0.001s. CompactLogix uses only.001s Preset value (pre): is the value up to which the timer will time. Preset value (pre): is the value up to which the timer will time. Accumulated value (ACC): is the value that increments as the timer is timing. This value can range from 0 to +32,767. Accumulated value (ACC): is the value that increments as the timer is timing. This value can range from 0 to +32,767. Done (DN) bit: Changes state whenever.PRE=.ACC value Done (DN) bit: Changes state whenever.PRE=.ACC value Enable (EN) bit: is on when the timer instruction is true. Enable (EN) bit: is on when the timer instruction is true. Timer timing(TT) bit: is on when the timer is timing. Timer timing(TT) bit: is on when the timer is timing.

19. Timer memory structure SLC 500 timer memory structure CompactLogix timer memory structure

20. On delay timer instruction When the TON is true, it will write a "1" to the EN (Enable). When the TON is true, it will write a "1" to the EN (Enable). If the TON is true and the ACC (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a "0" to the DN (Done) bit. If the TON is true and the ACC (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a "0" to the DN (Done) bit. If the TON is true and the ACC (Accumulated) is greater than the PRE (Preset), the TON will write a "0" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit. If the TON is true and the ACC (Accumulated) is greater than the PRE (Preset), the TON will write a "0" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit. The processor resets the accumulated value when the TON is false. The processor resets the accumulated value when the TON is false. Reset instruction (RES), will reset the timer at any time. Reset instruction (RES), will reset the timer at any time.

21. Off-Delay Timer When a TOF is true, it will write a "0" to the accumulated value, a "1" to the EN (Enable), a "0" to the TT (Timer Timing), and a "1" to the DN (Done) bit. When a TOF is true, it will write a "0" to the accumulated value, a "1" to the EN (Enable), a "0" to the TT (Timer Timing), and a "1" to the DN (Done) bit. When the TOF is false, it will write a "0" to the EN (Enable). When the TOF is false, it will write a "0" to the EN (Enable). If the TOF is false and the ACC (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit. If the TOF is false and the ACC (Accumulated) is less than the PRE (Preset), the TON will write a "1" to the TT (Timer Timing) bit and a "1" to the DN (Done) bit. If the TOF is false and the ACC (Accumulated) is greater than the PRE (Preset), the TOF will write a "0" to the TT (Timer Timing) bit and a "0" to the DN (Done) bit. If the TOF is false and the ACC (Accumulated) is greater than the PRE (Preset), the TOF will write a "0" to the TT (Timer Timing) bit and a "0" to the DN (Done) bit. A reset instruction resets the timer A reset instruction resets the timer

22. Off delay timer operation

23. Retentive timer The RTO instruction begins timing when it rung goes true. As long as the rung remains true, the timer updates the accumulated value each program scan, until it reaches the preset value. The RTO instruction retains its accumulated value even if one of the following occurs: the rung goes false the rung goes false you change to Program mode you change to Program mode the processor faults of loses power the processor faults of loses power

24. SLC 500 Timer addressing Example T4:0 means that it references an internal Timer file T4:0 means that it uses the first Timer in the table T4:0/DN means that it references the Done bit. T4:0/EN means that it references the Enable bit. T4:0/TT means that it references the Timer Timing bit. T4:0.ACC means that it references the 16 bit Accumulated value. T4:0.PRE means that it references the 16 bit Reset value.