Logix 500 Timer Question
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drbitboy
Lifetime Supporting Member
I'm not sure I understand.
I think you seem to be saying that you want
Is that correct?
I think you seem to be saying that you want
- a two-minute [T4:50] delay between
- the [Lube System I:0.4 changing from 0 to 1] event
- and [assigning 1 to O:0/0 via the OTE on rung 0000]
- You don't want that [T4:50] delay to occur less than 12h after the last time that [T4:50] delay occurred.
Is that correct?
Ken Moore
Lifetime Supporting Member
Assuming you can be off a second or two in you 12 hour time. You could set up a timer that had a preset of 3600 (1 hour) count the done bits and when you get to 12, enable your other logic. Afterwards reset timer and the count.
drbitboy
Lifetime Supporting Member
[Update: I forgot to put the [pXIC I:0/4] in series with the [LES ct12h 12] in that blue [OR] branch around the [XIC T4:50.DN] on the original rung 0000]
[Update II: fixed]
12h is 43,200s, which may be too big for the (assumed signed INT) .Pre of a timer with a 1s base time.
It will require a few new quantities (I will use tag-based names for them for clarity here; you will need to assign them to their proper file elements e.g. TON [TON1h] might become your [T4:51])
I was not sure this approach would work,but since it is basically what Ken Moore suggested, it has a decent chance of being correct.
Caveats
[Update II: fixed]
12h is 43,200s, which may be too big for the (assumed signed INT) .Pre of a timer with a 1s base time.
It will require a few new quantities (I will use tag-based names for them for clarity here; you will need to assign them to their proper file elements e.g. TON [TON1h] might become your [T4:51])
- Timer TON1h
- INT ct12h
I was not sure this approach would work,but since it is basically what Ken Moore suggested, it has a decent chance of being correct.
Caveats
- There may still be some edge cases where it fails.
- Specifically, the logic in front of the TON [TON1h] may not play well with the logic that assigns 0 to ct12h on the last rung
- It may work better if that last rung is triggered on a one-shot of T4:50.DN
- It feels more complex than necessary, but if nothing else it is a starting point.
Code:
########################################################################
### Assume PLC has been off for at least 12h: set 12h counter to 12
First Pass
S:1/15 ______________
----] [-----------[MOV ]----
[Source 12]
[Dest ct12h]
--------------
########################################################################
### Modify Rung 0000 from post #0: OR ct12h comparison with T4:50.DN (in blue)
T4:23 I:1 I:0 B3:3 I:0 T4:50 O:0
---] [-----] [----+----] [----+----] [----+---] [---+---+---] [---------------------+-----( )---
DN 1059 | 8 | 10 | 4 | | DN | 0
| | | | | |
| B3:7 | | B3:6 | [COLOR=Blue][B]| I:0 ______________ |[/B][/COLOR]
+----] [----+ +---] [---+ [COLOR=blue][B]+---] [---[LES ]--+[/B][/COLOR]
4 8 [COLOR=Blue][B] 4 [SourceA ct12h][/B][/COLOR]
[COLOR=blue][B][SourceB 12][/B][/COLOR]
[COLOR=blue][B] --------------[/B][/COLOR]
########################################################################
### No change to Rung 0001 from post #0
I:0 ______________
---] [-----------------[TON ]--(EN)--
4 [Timer T4:50]
[Time Base 1.0]--(DN)--
[Preset 120]
--------------
########################################################################
### Start a 1h (=3600s), repeating, self-sealing, timer [TON1h] when
### - ct12h is 0
### AND
### - T4:50 is done
### Repeat until 12h have elapsed
T4:50 ______________ ______________ TON1h ________________
---+----] [-------[EQ ]-------+--[LES ]------]/[------[TON ]--(EN)--
| DN [SourceA ct12h] | [SourceA ct12h] DN [Timer TON1h]
| [SourceB 0] | [SourceB 12] [Time base 1.0]--(DN)--
| -------------- | -------------- [Preset 3600]
| ______________ ______________ | ----------------
+-[GRT ]--[LES ]--+
| [SourceA ct12h] [SourceA ct12h] |
| [SourceB 0] [SourceB 12] |
| -------------- -------------- |
| |
| TON1h |
+----] [------------------------------+
DN
########################################################################
### When [T1h.DN] becomes 1, increment ct12h up to 12
______________ TON1h ______________
----[LES ]----------] [--------[ADD ]--------------
[SourceA ct12h] DN [SourceA ct12h]
[SourceB 12] [SourceB 1]
-------------- [Dest ct12h]
--------------
########################################################################
### Restart 12h counter, from 12, when 2minute delay (T4:50] is done
T4:50 ______________ _____________
--------] [-------[EQ ]----------[MOV ]---
DN [SourceA ct12h] [Source 0]
[SourceB 12] [Dest ct12h]
-------------- -------------
Last edited:
drbitboy
Lifetime Supporting Member
Corrected in blue a typo below: the seal-in branch at the start of the TON instruction for Timer TON1h should be TON1h.TT, not TON1h.DN.
Update: the first [LES ct12h 12] in the initial middle branch of the rung with the TON1h TON instruction is redundant with the instruction following the branch.
Update: the first [LES ct12h 12] in the initial middle branch of the rung with the TON1h TON instruction is redundant with the instruction following the branch.
Code:
...
########################################################################
### Start a 1h (=3600s), repeating, self-sealing, timer [TON1h] when
### - ct12h is 0
### AND
### - T4:50 is done
### Repeat until 12h have elapsed
T4:50 ______________ ______________ TON1h ________________
---+----] [-------[EQ ]-------+--[LES ]------]/[------[TON ]--(EN)--
| DN [SourceA ct12h] | [SourceA ct12h] DN [Timer TON1h]
| [SourceB 0] | [SourceB 12] [Time base 1.0]--(DN)--
| -------------- | -------------- [Preset 3600]
[B][COLOR=Blue] | ______________ | [/COLOR][/B] ----------------[B][COLOR=Blue]
+-[GRT ]--------------------+
| [SourceA ct12h] |
| [SourceB 0] |
| -------------- |[/COLOR][/B]
| |
| TON1h |
+----] [------------------------------+
TT
...
########################################################################
### Start a 1h (=3600s), repeating, self-sealing, timer [TON1h] when
### - ct12h is 0
### AND
### - T4:50 is done
### Repeat until 12h have elapsed
T4:50 ______________ ______________ TON1h ________________
---+----] [-------[EQ ]-------+--[LES ]------]/[------[TON ]--(EN)--
| DN [SourceA ct12h] | [SourceA ct12h] DN [Timer TON1h]
| [SourceB 0] | [SourceB 12] [Time base 1.0]--(DN)--
| -------------- | -------------- [Preset 3600]
| ______________ ______________ | ----------------
+-[GRT ]--[LES ]--+
| [SourceA ct12h] [SourceA ct12h] |
| [SourceB 0] [SourceB 12] |
| -------------- -------------- |
| |
[COLOR=Blue][B] | TON1h |[/B][/COLOR]
[B][COLOR=Blue] +----] [------------------------------+
TT[/COLOR][/B]
...
Last edited:
drbitboy
Lifetime Supporting Member
And here is an alternate approach, using a CTU; it's a bit cleaner because [XIC CTL12.DN] replaces [EQ ctl12h 12].
That said, and with the caveat that I know nothing about your process, I noticed that the two-minute [T4:50] delay was from [Lube Stream I:0/4] going to 1 and output [O:0/0]. If this is delaying the start of a motor and its driven rotating machinery until a lube stream has been running for two minutes, then you should be very careful about implementing this change. In fact, even using a delay for such a purpose could be risky. It would be much better to monitor the pressure of the lubricating fluid and not starting until that pressure reached the level where it lifts the shaft off the bearing (or journal or whatever). It might also be advisable to ensure the lube pressure transitions from a low value to a high value when [Lube Stream I:4/0] becomes 1, so that a faulty pressure sensor (if not two parallel pressure sensors) doesn't indicate a false high pressure and fool the system into starting up.
Unless some number of two-minute delays are more costly than an the downtime it takes to replace a ruined bearing, I would be very careful about implementing this change. For example, in a large ball mill a ruined bearing could cost millions of dollars, and even without inhibiting the delay, using a delay to ensure lubrication is not a good practice.
Again, I don't know your process, so I provide this sample code as-is and as my best effort to answer simply the question of your original post, and leave it to your organization to evaluate whether it is advisable to use it or anything like it.
That said, and with the caveat that I know nothing about your process, I noticed that the two-minute [T4:50] delay was from [Lube Stream I:0/4] going to 1 and output [O:0/0]. If this is delaying the start of a motor and its driven rotating machinery until a lube stream has been running for two minutes, then you should be very careful about implementing this change. In fact, even using a delay for such a purpose could be risky. It would be much better to monitor the pressure of the lubricating fluid and not starting until that pressure reached the level where it lifts the shaft off the bearing (or journal or whatever). It might also be advisable to ensure the lube pressure transitions from a low value to a high value when [Lube Stream I:4/0] becomes 1, so that a faulty pressure sensor (if not two parallel pressure sensors) doesn't indicate a false high pressure and fool the system into starting up.
Unless some number of two-minute delays are more costly than an the downtime it takes to replace a ruined bearing, I would be very careful about implementing this change. For example, in a large ball mill a ruined bearing could cost millions of dollars, and even without inhibiting the delay, using a delay to ensure lubrication is not a good practice.
Again, I don't know your process, so I provide this sample code as-is and as my best effort to answer simply the question of your original post, and leave it to your organization to evaluate whether it is advisable to use it or anything like it.
Code:
########################################################################
### Assume PLC has been off for at least 12h: set 12h counter to 12
### - This should force two-minute delay on next time I:0/4 is 1
### - N.B. can MOV write to counter Control .ACCumulator element?
### - If not, replace this [First Scan] rung with a RESet and a
### loop to increment CTL12.ACC to 12 manually
First Scan
S:1/15 __________________
----] [-----------[MOV ]----
[Source 12]
[Dest CTL12.ACC]
-----------------
########################################################################
### Modify Rung 0000 from post #0:
### - Add OR branch [XIC I:0/4 XIO CTL12.DN] to T4:50.DN
### - This will bypass delay for 12h since last delay rising edge
T4:23 I:1 I:0 B3:3 I:0 T4:50 O:0
---] [-----] [----+----] [----+----] [----+---] [---+---+---] [-----------+-----( )---
DN 1059 | 8 | 10 | 4 | | DN | 0
| | | | | |
| B3:7 | | B3:6 | | I:0 CTL12 |
+----] [----+ +---] [---+ +---] [-----]/[---+
4 8 4 DN
########################################################################
### Two-minute delay of [I:0/4]; no change to Rung 0001 from post #0
I:0 ______________
---] [-----------------[TON ]--(EN)--
4 [Timer T4:50]
[Time Base 1.0]--(DN)--
[Preset 120]
--------------
########################################################################
### Save one-shot rising edge of 2-minute delay done bit
T4:50 _____________________
--------] [-------[OSR ]------
DN [Storage bit B?:?/?]
[Output bit DelayOSR]
---------------------
########################################################################
### Start a 1h (=3600s), repeating, self-sealing, timer [TON1h] on
### - [XIC DelayOSR EQU CTL12.ACC 0] => first delay after CTL12 reset
### - [XIC TON1h.TT] seals-in running timer to complete first 1h cycle
### - [GRT CTL12.ACC 0] start repeat each of next 11 cycles
### - [XIO TON1h.DN] resets timer at end of each cycle
### - [XIO CTL12.DN] stops repeat after 12th cycle
### - TON1h.DN rising edge will increment CTL12.ACC
### - N.B. [EQU CTL12.ACC 0] may not be necessary
DelayOSR __________________ TON1h CTL12 ________________
---+----] [-------[EQU ]---+----]/[---------]/[------[TON ]--(EN)--
| [SourceA CTL12.ACC] | DN DN [Timer TON1h]
| [SourceB 0] | [Time base 1.0]--(DN)--
| ------------------ | [Preset 3600]
| | ----------------
| TON1h |
+----] [------------------------------+
| TT |
| |
| __________________ |
+---[GRT ]--------------+
[SourceA CTL12.ACC]
[SourceB 0]
------------------
########################################################################
### [TON1h.DN] rising edge increments counter up to 12 (CTL12.ACC),
### indicating approximately 12h have passed since last delay OSR
TON1h ______________
------] [--------[CTU ]---(CU)---
DN [Counter CTL12]
[Preset 12]---(DN)---
[Accum 0]
--------------
########################################################################
### Reset CTL12 counter, when complete & delay has rising edge
CTL12 DelayOSR CTL12
--------] [-------] [---------------[RES]------
DNjanner_10
Lifetime Supporting Member
This. KISS
drbitboy
Lifetime Supporting Member
Yes, my implementation added 18 rungs, which seems like too many for KISS, but almost half of those are getting around the [12h = 43,400s > maximum INT (32,767) for TON Preset] issue.
Also, I think my last rung, the counter reset, should move up two rungs, to just after the OSR instruction.
Oh dear, I just found another problem with my code: if the [Lube Stream I:04] becomes 1 at 11h59m after the 12h timer/counter process started, the order of events will be
- 11:59 [output O:0/0] will become 1 (on)
- 11:59 [T4:50] delay timer will start
- 12:00 [CTL12.DN] will become 1 as 12h counter completes
- 12:00 [output O:0/0] will become 0 (off)
- 12:01 [T4:50.DN] will become 1 as delay timer completes
- 12:01 [output O:0/0[ will become 1 (on)
So it's now 19 instructions to add the OP's requested behavior, but this kind of creep makes me think this approach is not KISS.
Code:
########################################################################
### Assume PLC has been off for at least 12h: set 12h counter to 12
### - This should force two-minute delay on next time I:0/4 is 1
### - N.B. can MOV write to counter Control .ACCumulator element?
### - If not, replace this [First Scan] rung with a RESet and a
### loop to increment CTL12.ACC to 12 manually
First Scan
S:1/15 __________________
----] [-----------[MOV ]----
[Source 12]
[Dest CTL12.ACC]
-----------------
########################################################################
### Modify Rung 0000 from post #0:
### - Add OR branch [XIC I:0/4 XIO CTL12.DN] to T4:50.DN
### - This will bypass delay for 12h since last delay rising edge
T4:23 I:1 I:0 B3:3 I:0 T4:50 O:0
---] [-----] [----+----] [----+----] [----+---] [---+---+---] [--------------+-----( )---
DN 1059 | 8 | 10 | 4 | | DN | 0
| | | | | |
| B3:7 | | B3:6 | | I:0 CTL12 |
+----] [----+ +---] [---+ +---] [--+---]/[---+-+
4 8 4 | DN |
[COLOR=Blue][B]| |
| O:0 |
+---] [---+
0
[/B][/COLOR]
########################################################################
### Two-minute delay of [I:0/4]; no change to Rung 0001 from post #0
I:0 ______________
---] [-----------------[TON ]--(EN)--
4 [Timer T4:50]
[Time Base 1.0]--(DN)--
[Preset 120]
--------------
########################################################################
### Save one-shot rising edge of 2-minute delay done bit
T4:50 _____________________
--------] [-------[OSR ]------
DN [Storage bit B?:?/?]
[Output bit DelayOSR]
---------------------
########################################################################
### Reset CTL12 counter, when complete & delay has rising edge
CTL12 DelayOSR CTL12
--------] [-------] [---------------[RES]------
DN
########################################################################
### Start a 1h (=3600s), repeating, self-sealing, timer [TON1h]
### - [XIC DelayOSR EQU CTL12.ACC 0] => first delay after CTL12 reset
### - [XIC TON1h.TT] seals-in running timer to complete first 1h cycle
### - [GRT CTL12.ACC 0] start repeat each of next 11 cycles
### - [XIO TON1h.DN] resets timer at end of each cycle
### - [XIO CTL12.DN] stops repeat after 12th cycle
### - TON1h.DN rising edge will increment CTL12.ACC
### - N.B. [EQU CTL12.ACC 0] on first branch may not be necessary
DelayOSR __________________ TON1h CTL12 ________________
---+----] [-------[EQU ]---+----]/[---------]/[------[TON ]--(EN)--
| [SourceA CTL12.ACC] | DN DN [Timer TON1h]
| [SourceB 0] | [Time base 1.0]--(DN)--
| ------------------ | [Preset 3600]
| | ----------------
| TON1h |
+----] [------------------------------+
| TT |
| |
| __________________ |
+---[GRT ]--------------+
[SourceA CTL12.ACC]
[SourceB 0]
------------------
########################################################################
### [TON1h.DN] rising edge increments counter up to 12 (CTL12.ACC),
### indicating approximately 12h have passed since last delay OSR
TON1h ______________
------] [--------[CTU ]---(CU)---
DN [Counter CTL12]
[Preset 12]---(DN)---
[Accum 0]
--------------
Last edited:
drbitboy
Lifetime Supporting Member
One more approach
- Use RTC:0.HR to "measure" 12h
- but it is approximate: the period during which the two-minute delay is disabled can range from 11h to 13h.
- Adds 15 instructions, which still feels like a lot
- But only three rungs
- One for First Scan
- One to latch BypassDelay
- One to unlatch BypassDelay
- But only three rungs
Code:
########################################################################
### On first scan, unlatch Bypass Delay, which enables two-minute delay
First Scan
S:1/15 BypassDelay
----] [-----------(U)-----------
########################################################################
### Modify Rung 0000 from post #0:
### - Branch [XIC I:0/4 [XIC BypassDelay OR XIC O:0/0] around T4:50.DN
### - This will bypass delay for 12h since last delay rising edge
T4:23 I:1 I:0 B3:3 I:0 T4:50 O:0
---] [-----] [----+----] [----+----] [----+---] [---+---+---] [-----------------+-----( )---
DN 1059 | 8 | 10 | 4 | | DN | 0
| | | | | |
| B3:7 | | B3:6 | | I:0 BypassDelay |
+----] [----+ +---] [---+ +---] [--+----] [---+---+
4 8 4 | |
| O:0 |
+----] [---+
0
########################################################################
### Two-minute delay of [I:0/4]; no change to Rung 0001 from post #0
I:0 ______________
---] [-----------------[TON ]--(EN)--
4 [Timer T4:50]
[Time Base 1.0]--(DN)--
[Preset 120]
--------------
########################################################################
### When BypassDelay is off & delay has rising edge
### - Latch BypassDelay, which will bypass two-minute delay
### - Set the Fin12h value 12h hence, when BypassDelay will be unlatched
### - DlyStore ensures the above occurs on T4:50.DN rising edge only
T4:50 DlyStore BypassDelay BypassDelay
-------] [---+----]/[--------]/[-------+-------------(L)---------------------------+---
DN | | _________________ |
| +---[ADD ]---------------------+
| | [SourceA RTC:0.HR] |
| | [SourceB 12] |
| | [Dest Fin12h] |
| | ----------------- |
| | _______________ _______________ |
| +---[GRT ]---[SUB ]---+
| [SourceA Fin12h] [SourceA Fin12h] |
| [SourceB 23] [SourceB 24] |
| --------------- --------------- |
| |
| DlyStore |
+----( )--------------------------------------------------------------+
########################################################################
### Unlatch BypassDelay when ~12h have passed since last used delay
_________________ BypassDelay
---[EQU ]---------(U)------
[SourceA RTC:0.HR]
[SourceB Fin12h]
-----------------
Last edited:
The lube system is for a cone crusher, there are pressure transmitter's on the lube system that indicate flow/pressure. The customer had a cone at another facility have a catastrophic failure because someone jumped out the safety circuit and they wanted the two minute timer to allow for extra circulation of the lube system. I told them that it didn't really matter because the pressure transmitter is what they need to pay attention to. I am sure the transmitter is in the logic as an enable but I can't really tell because nothing is tagged in the logic.
drbitboy
Lifetime Supporting Member
Thanks for the explanation; so I:0/4 would not be 1 until there is adequate pressure in the lube system to ensure flow, valves are open, etc. Nice.
Someone jumped out the safety circuit at another site? Ouch!
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