AB SLC-500 Beginner Questions

[2k1Toaster]

Do you know of anyone that would be willing to make a simpler actual flowchart of what needs to be done to get those timers reset? I am almost at the point where I just need it to work, not understand it since I will never use it again. I tried setting N:11 to a value of 4, just to see what would happen, and it didn't seem to change at all.

I have most of the code working. The 3 things that I currently do not know how to do:

1) Have the program automatically turn off. This is with the timers you are explaining above, but I don't see it turning off even with the pre-load of N:11. Perhaps it is moving the value before I set it because of the order of my operations.

2) Be able to stop the program (STOP_ALL?) and then able to start again. If I set the "B3:0/14" bit to 1, the system shuts down and all is well. However I cannot then get it to start back up again.

3) The WARMUP_NEEDED "B3:1/6" or WARMUP_NOT_NEEDED "B3:1/7" bit does change sometimes, but only with the old system connected. So again I believe this is a timer problem where it never gets set because the timer isn't set properly, but I don't know.

 

[Lancie1]

Do you know of anyone that would be willing to make a simpler actual flowchart of what needs to be done to get those timers reset?

The problems you are having are due to the fact that you have 2 programs to deal with - the RSLogix500 program "Broadmoor 4-15-04" that you have in hand, and the unknown HMI program that issued the Stop and Start signals and also set the various values for the timers and counters. Really the PLC program will work as is IF you can figure out all the bells and whistles that are on the other end, issuing commands to the PLC program. These two programs have to work together as a team. You cannot use one without the other, and you cannot change one without making sure that the other program will not be affected and can still operate.

If you are serious about getting it to work, then you really need some type of cheap HMI graphic operator panel (Red Lion brand maybe) to connect to the PLC, with the Start, Stop, and other controls that the PLC is looking for. Witout those being online and interactive, the PLC program as is cannot work.

1) Have the program automatically turn off. This is with the timers you are explaining above, but I don't see it turning off even with the pre-load of N:11.

The actual "Cycle Timer Preset" is PLC memory word N11:0. I suspect that this value is set and controlled by a box on the operator panel that asks "Enter the Number of Intervals: [___]". Whatever the operator entered in that box is moved to PLC memory location N11:0, which is was "-21846" in the old program, which has to be an error because a timer Preset should never be less than 0 (negative time is not logical). You can manually enter a value there from the RSLogix program by going to address N11:0 and typing it in. I manually entered "15" in the attached Rev. 1 program. I also set N11:39 from "0" to "20" cycles. These settings should make it run better.

2) Be able to stop the program (STOP_ALL?) and then able to start again. If I set the "B3:0/14" bit to 1, the system shuts down and all is well. However I cannot then get it to start back up again.

Yes, if you set B3:0/14 to 1, that was the STOP command from the old HMI. To make it Start again, then (on Rung 19) you would have to reset B3:0/14 back to 0, and then set the "Start from PM" bit B3:0/8 to 1. If you use B3:0/8, then there were 4 other "Latches" controlled by the PLC (Tonic Latch, Relax Latch, Shape Latch, and Release Latch), one of which had to be ON in order to restart with the "Start from PM" bit. These latches are controlled by user interface input bits B3:0 to B3:3.

3) The WARMUP_NEEDED "B3:1/6" or WARMUP_NOT_NEEDED "B3:1/7" bit does change sometimes, but only with the old system connected. So again I believe this is a timer problem where it never gets set because the timer isn't set properly, but I don't know.

Doing a global Search in your RSLogix program, address B3:1/6 was not found. B3:1/6 is not used by the PLC program, although it is labeled in PLC memory as "Warmup Needed". This indicates that it was used at one time (and may be been set by the HMI controls). Now it has been removed from the PLC logic. Bit B3:1/7 "Warmup Not Needed" is controlled by rung 21 (which in turn is controlled by the Off-Delay Timer T4:1 (it starts timing when its input trigger goes OFF) and also the Warm Up Latch B3:0/13. Tracing it to the next level, the Warm Up Latch is controlled by Rung 17 (which is activated by a "Start Warm Up" button (bit B3:0/12) on the old PM HMI panel. When the the "Warm Up From PM" bit on Rung 17 is ON, the "Warm Up Latch" goes on for 15 seconds as controlled by Timer T4:12. After 12 seconds, the "Warm Up Not Needed" bit on Rung 21 should go on. That sort of makes sense, as the Warm Up process has been run for 12 of the 15 seconds at that point.

Remember that a lot of these B3:0 bits were probably buttons (and indicator lights) on the HMI panel that the operator pressed ON or OFF, so labeled buttons would make it a lot easier to see what needs pressing to start and stop the process and also control the other latches.

 

[2k1Toaster]

Thankyou for your help.

The problems you are having are due to the fact that you have 2 programs to deal with - the RSLogix500 program "Broadmoor 4-15-04" that you have in hand, and the unknown HMI program that issued the Stop and Start signals and also set the various values for the timers and counters. Really the PLC program will work as is IF you can figure out all the bells and whistles that are on the other end, issuing commands to the PLC program. These two programs have to work together as a team. You cannot use one without the other, and you cannot change one without making sure that the other program will not be affected and can still operate.

I do have the old unit. I have built a replacement unit using new hardware, and written new software from the ground up. I can see what registers are being set to what with the old unit. I am not going to a solo setup, just replacing 20+ year old user interface hardware with something more modern.

If you are serious about getting it to work, then you really need some type of cheap HMI graphic operator panel (Red Lion brand maybe) to connect to the PLC, with the Start, Stop, and other controls that the PLC is looking for. Witout those being online and interactive, the PLC program as is cannot work.

I have already done this. I have built it. I am at the final stage now. I can press a button on my new hardware and the program starts. It just doesn't stop. I can press the warmup button, and it does warmup. It just doesn't tell me it is done, even though I can see the temperatures.

The actual "Cycle Timer Preset" is PLC memory word N11:0. I suspect that this value is set and controlled by a box on the operator panel that asks "Enter the Number of Intervals: [___]. Whatever the operator entered in that box is moved to PLC memory location N11:0, which is was "-21846" in the old program, which has to be an error because a timer Preset should never be less than 0. You can manually enter a value there from the RSLogix program by going to address N11:0 and typing it in. I manually entered "15" in the attached program.

There is no input other than the "PM" registers (the ones that end in "PM") Everything else is hard coded in either the PLC or the source code to the user interface.

I did just realize that I am not polling the "N" registers in my copy of a cold boot. I realized the user interface was probably setting up variables so I pull all the B and S type variables, but not the N. I will have to do that. But I manually wrote N11:0 to 4 (and to 15) and there was no change in behaviour.

Yes, if you set B3:0/14 to 1, that was the STOP command from the old HMI. To make it Start again, then (on Rung 19) you would have to reset B3:0/14 back to 0, and then set EITHER the "System Latch" B3:0/15 OR the "Start from PM" bit B3:0/8. If you use B3:0/8, then there were 4 other "Latches" (Tonic Latch, Relax Latch, Shape Latch, and Release Latch), one of which had to be ON in order to restart with the "Start from PM" bit.

I pretty much did that, and it didn't start. I think there is another variable that has to be set. I set the stop bit. I then unset it. To start another program you have to press the from PM bits that then set the latch bits you describe. Perhaps I have to manually set the latch bits instead of the PM bits after a stop... I guess I can try that.

Doing a global Search in your RSLogix program, address B3:1/6 was not found. B3:1/6 is not used by the PLC program, although it is labeled in PLC memory as "Warmup Needed". This indicates that it was used at one time (and may be been set by the HMI controls). Now it has been removed from the PLC logic. Bit B3:1/7 "Warmup Not Needed" is controlled by rung 21 (which in turn is controlled by the Off-Delay Timer T4:1 (it starts timing when its input trigger goes OFF) and also the Warm Up Latch B3:0/13. Tracing it to the next level, the Warm Up Latch is controlled by Rung 17 (which is activated by a "Start Warm Up" button (bit B3:0/12) on the old PM HMI panel. When the the "Warm Up From PM" bit on Rung 17 is ON, the "Warm Up Latch" goes on for 15 seconds as controlled by Timer T4:12. After 12 seconds, the "Warm Up Not Needed" bit on Rung 21 should go on. That sort of makes sense, as the Warm Up process has been run for 12 of the 15 seconds at that point.

I don't see the Warmup not needed bit ever get set, but it does go through the motions. This descriptions pretty much agrees with my hypothesis that I am missing the timer initializations.

Remember that a lot of these B3:0 bits were probably buttons on the HMI panel that the operator pressed ON or OFF, so labeled buttons would make it a lot easier to see what needs pressing to start and stop the process and also control the other latches.

I have the old interface and the new interface and mimic all on-screen buttons. There are only a couple remaining pieces to the puzzle.

Thanks again!

 

[Lancie1]

I pretty much did that, and it didn't start. I think there is another variable that has to be set. I set the stop bit. I then unset it. To start another program you have to press the from PM bits that then set the latch bits you describe. Perhaps I have to manually set the latch bits instead of the PM bits after a stop... I guess I can try that.

The 3 NC bits B3:0/13, B3:0/14, and C5:1/DN on the left side of Rung 19 have to be "0" (electrically closed). It could be that the C5:1 Counter is not gettting RESET when you Stop then restart. The counter should be reset on Rung 24 when the System Latch is turned from RUN ("1") to STOP ("0").

Also bit B3:4/14 "Stop All Individual" has to be 0 in order to restart. It is not set or reset anywhere in the PLC program, so must be controlled by your user interface.

To make it Start again, then (on Rung 19) you would have to reset B3:0/14 back to 0, and then set EITHER the "System Latch" B3:0/15 OR the "Start from PM" bit B3:0/8.

I was wrong about that. B3:0/15 should NOT be set or controlled by your user interface. It is controlled by the PLC program on Rung 19. That means to start or restart it, you must set the B3:0/8 "Start From PM" bit to "1", and make sure that B3:0/14, B3:0/15, C5:1/DN, and B3:0/15 are all OFF or "0".

The four B3:12 to B3:15 bits (at least 1 ON needed for Rung 19 start) are controlled by the PLC program responding to user interface input bits B3:0/0, B3:0/1, B3:0/2, and B3:0/3.

 

[2k1Toaster]

Whatever the operator entered in that box is moved to PLC memory location N11:0, which is was "-21846" in the old program, which has to be an error because a timer Preset should never be less than 0 (negative time is not logical). You can manually enter a value there from the RSLogix program by going to address N11:0 and typing it in. I manually entered "15" in the attached Rev. 1 program. I also set N11:39 from "0" to "20" cycles. These settings should make it run better.

Can you please explain how you know it is N11:0? Searching in the PDF output, the only N11 I see is N11:39.

I am just trying to understand that. I am going to the unit tonight and will try to read N11:0 to see what it is set to before and after the old unit's initialization. I just don't see the mapping between the old value in the output to N11. I don't disagree it is there, I just am not sure how to interpret the PDF to get that output.

 

[Lancie1]

Can you please explain how you know it is N11:0? Searching in the PDF output, the only N11 I see is N11:39.

Yes I can. On Rung 022, there is a MOV (Move) instruction that moves the value of N[11]:[0] (which is equal to direct address N11:0) to the Timer T4:0 Preset Value when the System Latch is ON. In other words, Timer T4:0 gets changed to a timing range of 0 to N11:0 (which I think should be set to "15", but definitely NOT a negative number such as "-21846", for the first PLC run). I suppose in the original, the value of N11:0 is supposed to be set somewhere in the operator interface program.

By making the direct address N11:0 into an Indirect Address by adding the brackets [], some slick programmer made it so that a Search would not find N11:0. That makes it apeear that N11:0 does not exist in this program, but it does. I hate to see guys that do stuff like that simply to confuse the uninitiated.

 

[2k1Toaster]

Yes I can. On Rung 022, there is a MOV (Move) instruction that moves the value of N[11]:[0] (which is equal to direct address N11:0) to the Timer T4:0 Preset Value when the System Latch is ON. In other words, Timer T4:0 gets changed to a timing range of 0 to N11:0 (which I think should be set to "15", but definitely NOT a negative number such as "-21846", for the first PLC run). I suppose in the original, the value of N11:0 is supposed to be set somewhere in the operator interface program.

By making the direct address N11:0 into an Indirect Address by adding the brackets [], some slick programmer made it so that a Search would not find N11:0. That makes it apeear that N11:0 does not exist in this program, but it does. I hate to see guys that do stuff like that simply to confuse the uninitiated.

Oh I see. It is first retrieving the value of N7:53 which is 11, and that's how you were getting N11. Then C5:1.ACC is 0, so it is N11:0. I didn't realize you could address things that way, but that makes sense now.

So last night I spent another 2 hours wrangling with this and got nowhere again.

First I was trying to get the warmup cycle. Starting from a "ready" system that has been initialized by the old unit, I can press the Warm Up From PM (B3:0/12) and it does warm up the valves. However, it never shuts off.

I am trying to learn the file and breaking it down to getting the warmup cycle to work first. I took a hard look at the PDF file and this is the best I have come up with so far:

I see rung 0017. To me this says either the "Warm Up From PM B3:0/12" or "Warm Up Latch B3:0/13" has to be set to 1. "Stop All B3:0/14" has to be set to 0. The "Warm Up Sequence T4:12/DN" has to be set to 0. This is the timer "done" bit correct? Can I reset this myself? I seem to be able to write it to 0, but I don't know if you have to interact with timers differently like clearing something else which then itself makes it done. Then the "System Latch B3:0/15" has to be 0. This will make the Warm Up Sequence TON Timer T4:12 start ticking. It counts every 10ms (Timer Base of 0.01) from 0 (T4:12/ACC) to 1500 for a total of 15 seconds. Or does it go from 1500 to 0? I have seen references on the web that say it counts down, others say it counts up. Does this also then mean I have to "reset" the timer with the starting value before making the stuff before it true? When all this happens, then the "Warm Up Latch B3:0/13" will latch on.

I don't really get the interaction between the timer block in parallel with the "Warm Up Latch B3:0/13" output. Is that a "if one is false, the other is false"? I see that "EN", so "T4:12.EN" is tied to the output as well...

Then if I go down to rung 0020 it uses the "Warm Up Latch B3:0/13" to start the TOFF timer T4:1 "Warm Up Needed T". Then that timer counts down from 1200 to 8 every second? So it will take about 20 minutes? I am guessing this timer value needs to be preset to something so it only takes 1-2 minutes, not 20 if I read that properly.

Then I look on rung 0036, if T4:12.ACC is between 10 and 25, then it puts some temperature values on the valves and sets the "Warm Up Temp Set B3:0/11". Then on rung 0037, if T4:12.ACC is between 30 and 45, it then sets the flow rate for those valves and sets the "Warm Up Flow Set B3:0/10".

Then on Run 0038, if T4:12.ACC is greater than 50, then "Warm Up Delay B3:0/9" gets set.

Rungs 0036, 0037, and 0038 depend on "Warm Up Latch B3:0/13" being set, which it should have been on rung 0017 that started this whole thing,

Rungs 0039 through 0055 do something with the "Warm Up Flow Set" and "Warm Up Temp Set" bits that were set in 0036 and 0037 to put some data somewhere internally. Not quite sure if that is something special, or just internal housekeeping.

Then rung 0057 uses the "Warm Up Delay B3:0/9" to start the T4:2 TOFF timer. It counts every second from 1 to 1? So I am guessing this needs to be set externally to something else to tell it how long before that timer expires and turns stuff off?

And then on 0058, when "Delay Off Valve T4:2.DN" is set to 1 and "Stop Zone 1 B3:3/6" + "Stop All Individual B3:4/14" are not set, it will set some internal bit "Start Out Valve Start = 1"?

Same sort of deal with the same weird timers for 0060, 0061, and 0062 for Zone 2. Again the same with 0063, 0064, and 0065 for Zone 3. And again with 0066, 0067,and 0068 for Zone 4. Again with 0069, 0070, and 0071 for Zone 5. And once more with 0072, 0073, and 0074 for Zone 6. I guess I will need to set all these weird timers to something non-1 so that it actually does count and turn on then delay off right?

Rung 0075 doesn't seem to matter for Warm Up since it requires the System Latch of B3:0/15 to be on which only gets set with the actual programs from the PM which the Warmup is not. I don't see that being set anywhere else in code but rung 0019. Rungs 0076 and 0077 require the "Sequence Temp Se B3:4/0" bit to be set to do anything which only gets set on 0075. So again I will ignore those for warmup purposes. 0077 sets the "Sequence Flow Se B3:4/1" bit, so I can ignore rung 0078 as well.

It looks like Rung 0079 allows you to individually set the temperature of Valve 6 as long as lots of other things aren't going on. Presumably to prevent people from changing it while the program is running... Rung 0080 does the same for Valve 5, 0081 for Valve 4, 0082 for Valve 3, 0083 for Valve 2, and then 0084 for Valve 1.

It looks like 0085 lets you turn all the valves on a low flow setting as long as they aren't set for other flow rates or in use already. 0086 for medium flow, 0087 for high flow. Again, nothing to do with warmup.

And looking at the rest of the rungs, it looks like that is the actual program part that changes the flow and temperatures depending on the time. That seems to just always do it when the program is on because when I have the problem of it not shutting off, it does seem to constantly adjust everything. So that looks all good.

Going through it, it appears that the thing I was missing was setting those "weird TOFF timers" like T4:2, T4:3, etc to values greater than 1. And then in the T4:1 timer, adjust that from the default of 20 minutes to something more reasonable if I read that properly.

Does this sound reasonable?

I appreciate all the help. Thanks!

 

[Lancie1]

The "Warm Up Sequence T4:12/DN" has to be set to 0. This is the timer "done" bit correct? Can I reset this myself?

You can, but the DN bit is always 0 or off anytime that a TON timer is off or deenergized. So when the "Warm Up From PM" B3:0/12 bit first goes on, T4:12/DN will be OFF, meaning that the XIO (Examime If Open wiill produce a 1 if the T4:12/DN bit is 0). So the XIO T4:12/DN instruction will be TRUE (making the circuit ON). Basically the B3:0/12 Starts the T4:12 Timer and seals the rung ON with the Warm UP Latch, until the timer hits 15 seconds and the T4:12/DN bit unseals the rung.

I don't really get the interaction between the timer block in parallel with the "Warm Up Latch B3:0/13" output.

The Warm Up Latch serves as a latch or seal-in to keep the circuit ON with its contact in parallel with the "Warm Up From PM" bit (which PM bit was probably a momentary pushbutton that goes on for a second then back off). In other words, this circuit is Started by the Warm Up From PM bit, but keep running by the Warm Up Latch, then Stopped by the T4:12/DN Timer bit. This is a common type of control circuit where you need to start something with one event, but then stop it with a totally separate event.

It counts every 10ms (Timer Base of 0.01) from 0 (T4:12/ACC) to 1500 for a total of 15 seconds. Or does it go from 1500 to 0?

Yes, all these RSLogix timers count from 0 up to the Preset Value.

Then if I go down to rung 0020 it uses the "Warm Up Latch B3:0/13" to start the TOFF timer T4:1 "Warm Up Needed T". Then that timer counts down from 1200 to 8 every second? So it will take about 20 minutes? I am guessing this timer value needs to be preset to something so it only takes 1-2 minutes, not 20 if I read that properly.

T4:1 is a TOF (Timer Off Delay) timer, meaning that it only runs when its trigger circuit goes from ON to OFF. So to make T4:1 start running, both the System Latch AND the Warm Up Latch have to be OFF. At that point, it should start timing and count up to 1200 seconds. When the program was printed, the value of T4:1 was "8" seconds, because it was in the process of counting up to 1200. (You should probably manually reset it to "0"). A TOF DN bit is true until the rung goes FALSE and the timer times up to the Preset, then the DN bit goes OFF. To sum up rung 20, when both System Latch and the Warm Up Latch have been OFF for 1200 seconds (= 200 minutes or 3 hours and 20 minutes), then the "Warm Up Not Needed" flag relay goes OFF. This logic seems to be backwards of what would be logical. It seems that after 200 minutes, that a warm-up would be needed (unless running keeps it warmed).

Then I look on rung 0036, if T4:12.ACC is between 10 and 25, then it puts some temperature values on the valves and sets the "Warm Up Temp Set B3:0/11". Then on rung 0037, if T4:12.ACC is between 30 and 45, it then sets the flow rate for those valves and sets the "Warm Up Flow Set B3:0/10".

The OTE coil for B3:0/11 does not SET or LATCH that bit, but only keeps it ON temporarily while the T4:12 timer is between 0.10 and 0.25 seconds. The CPT or Compute instructions calculate and send analog values to the various analog Outputs from O:3.0 to O:4.1. Again for Rung 37 B3:0/10, that bit is only ON temporarially while timer T4:12 is between 0.30 and 0.45 seconds. After time 0.45 seconds, bit B3:0/10 goes back OFF.

Then on Run 0038, if T4:12.ACC is greater than 50, then "Warm Up Delay B3:0/9" gets set.

Again, technically B3:0/9 is not SET or LATCHED (as it would be if the B3:0/9 coil (OTE Output Energize instruction) was instead a OTL Output Latch instruction. If the B3:0/9 coil on Rung 38 had been a OTL Latch instruction, it would have a big L in the center sort of like this: "---(L)---". Because it only stays ON while energized by the preceding logic, then when the timer tT:12 Accumulator value reaches "51", B3:0/9 goes OFF again.

Rungs 0039 through 0055 do something with the "Warm Up Flow Set" and "Warm Up Temp Set" bits that were set in 0036 and 0037 to put some data somewhere internally. Not quite sure if that is something special, or just internal housekeeping.

These rungs appear to be signals or external indicator lights that new analog data is Ready or Not Ready to be transferred to Valves 1 to 6 in Rungs 34 to 37. When any of the Outputs O:1/3, O:1/11, O:1/15, O:2/3, and O:2/7 are OFF, then data is ready to be transferred to the analog Output for that valve.

Then rung 0057 uses the "Warm Up Delay B3:0/9" to start the T4:2 TOFF timer. It counts every second from 1 to 1? So I am guessing this needs to be set externally to something else to tell it how long before that timer expires and turns stuff off?

T4:2 timer is a TOF Timer OFF Delay, so it only starts timing when both the parallel rung branches go from ON to OFF. When either B3:0/9 is ON, or Timer T4:9 is DONE and N7:41 memory word is greater than 60, the Timer T4:2 will reset its ACCUMulated value to 0 and turn on its DN bit, then wait until the rung goes FALSE. Then it will count to 1 again and turn off T4:2/DN. So it self-resets to 0 at the right time and you do not need to do anything to this timer.

Same sort of deal with the same weird timers for 0060, 0061, and 0062 for Zone 2. Again the same with 0063, 0064, and 0065 for Zone 3. And again with 0066, 0067,and 0068 for Zone 4. Again with 0069, 0070, and 0071 for Zone 5. And once more with 0072, 0073, and 0074 for Zone 6. I guess I will need to set all these weird timers to something non-1 so that it actually does count and turn on then delay off right?

Best I can tell, they are all okay as is. Off-Delay timers are non-intuitive and very confusing to think about logically. They start timing on negative or false logic (ON-to-OFF transition), instead of when something goes OFF-to-ON. The DN bit is ON when the timer is OFF, then DN goes OFF when the timer goes ON and and has timed out.

Rung 0075 doesn't seem to matter for Warm Up since it requires the System Latch of B3:0/15 to be on which only gets set with the actual programs from the PM which the Warmup is not. I don't see that being set anywhere else in code but rung 0019.

Correct, the System Latch bit B3:0/15 is only controlled by Rung 19. B3:0/15 is not SET, but self-seals itself ON until one of these bits turns it OFF: Warm Up Latch, Stop All, System Cycle Counter Done, Stop All Individual. SET would mean that a hard latch such as "---(L)---" or a OTL Output Latch instruction had been used as the rung output, instead of the OTE instruction. A OTL instruction requires a OTU Output Unlatch to turn it back OFF. A quick Search of the program did not find and OTL isntructions, so that are no hard Latches (or Sets) in this one.

Going through it, it appears that the thing I was missing was setting those "weird TOFF timers" like T4:2, T4:3, etc to values greater than 1.

Unfortunaltely I think the TOF timers are working as intended.

And then in the T4:1 timer, adjust that from the default of 20 minutes to something more reasonable if I read that properly.

the TOF timer T4:1.PRE = 1200 seconds = 200 minutes = 3 hours and 20 minutes! If you turn it on in warm-up mode, then it will turn ON the "Warm Up Not Needed" bit, and then wait 3 hours 20 minutes AFTER the Sytem Latch and the Warm Up Latch are OFF, before it turns B3:1/7 OFF again.

Does this sound reasonable?

Yes, it all sounds very reasonable! But as Mr. Spock said, some of it may not be logical. I wish I knew enough about the process to help you more, but a lot of it depends on exactly how those valves use the analog output varying signals.