Understanding how a PLC Program Scans in an Allen Bradley Micrologix using RsLogix 500

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Understanding how a PLC Program Scans in an Allen Bradley Micrologix using RsLogix 500

Рет қаралды 10,180

Tim Wilborne

Күн бұрын

Пікірлер: 34

@DDLazlo Жыл бұрын

Tim!! Wish I had discovered you 2 years ago. Older electrician here working to catch up. You rock!

@TimWilborne Жыл бұрын

That is great to hear Richard! Keep it up!

@ayushgairola5570 4 жыл бұрын

you're doing great job guys, thanks for the stuff!

@TimWilborne 4 жыл бұрын

You are welcome! Thanks for watching :)

@dougmahoney5872 2 жыл бұрын

Hi Tim! Good Video. You really to show how the program scan basically work. Like the program scans right to left top to bottom and cannot go back. This would be a general case. May help some beginning programmers…

@dwaynes5983 2 жыл бұрын

I just got off the phone last week helping a customer troubleshoot. After the run was finished the pumps and conveyor kept running. No body knew what the problem was. I found out the customer left the conveyor in Hand mode and confusing the plc program. All fixed now.

@danieljoun219 3 жыл бұрын

Thanks Tim! Great video

@TimWilborne 3 жыл бұрын

You are welcome Daniel!

@6ordon6 5 жыл бұрын

Good stuff Tim.

@TimWilborne 5 жыл бұрын

Thanks. It was a tough one to keep the enthusiasm going in but very important content.

@efrenpinedo9343 Жыл бұрын

How does the watchdog timer work within the plc scan cycle?

@TimWilborne Жыл бұрын

If any PLC scan time is greater than the watchdog, the PLC will fault.

@awaismunir6340 Жыл бұрын

Hello @Tim Just wanted to ask if PLC updates output data table as it is executing program and then update outputs at the end of program or it just does it at the end once it has finished executing the program. If it does so at the end then where does it stores its ouput values during the execution of program?

@TimWilborne Жыл бұрын

The data table is updated immediately when something in the ladder writes to it. The physical outputs are updated at the end of the PLC scan in the Micrologix and SLC 500. Controllogix and Compactlogix don't work this way.

@slipnorris5882 4 жыл бұрын

Hi beginner here. The output module has a 1 in the bit box. The reason is because there is current going to the input module to the output module or the 1 is already programmed into the processor by the software?

@TimWilborne 4 жыл бұрын

Not sure in following you but the input but box is in no way associated with the output bit box. You would to need to see what is putting a 1 into the output bit box.

@slipnorris5882 4 жыл бұрын

@@TimWilborne thanks for the reply, I just read a plc book , it threw me off, after watching videos on youtube, I have a better understanding.

@TimWilborne 4 жыл бұрын

@@slipnorris5882 Glad they helped!

@stanleypolanco4887 4 жыл бұрын

Regards Tim A question? I have an SLC 5/03 with a shelf of 10 slots The program that has been loaded into the PLC consists of 8 LADs included (SYS 0 and SYS 1). The problem is that at the time of running the program, it only runs until LAD 5 and LAD 6 and 7 DO NOT WORK. What do you think it is? Thank you

@TimWilborne 4 жыл бұрын

Hi Stanley. By default only Ladder 3 will be scanned. It sounds like you have JSR instructions for LAD 5, 6, and 7. There are other ways to call programs, it could be that ladder 4 and 8 are connected to some type of high speed interrupt.

@user-wt9xo5ys1m 4 жыл бұрын

Hey Tim, Thanks for your the great video! I am new on PLC stuff, how can I show the logic on the HMI if I get into the system as administrator? many thanks

@TimWilborne 4 жыл бұрын

Glad you like our video. We have a basic HMI series coming soon.

@user-wt9xo5ys1m 4 жыл бұрын

@@TimWilborne can you send me your email address I want to message you with pictures on some problems I got in the field you might help me with that.

@et.sachin 3 жыл бұрын

Do we need to keep an order while breaking down a program into multiple subroutines using JSR ? Like should i scan certain subroutine before another, does the order matter?

@TimWilborne 3 жыл бұрын

The order of the JSRs will affect the way the program is scanned. I would say in 80% of programs, the order is insignificant, but in that 20 percent, it can affect the outcome on the machine.

@iliapopovich 3 жыл бұрын

Hi, Mr. Tim, I'm wondering if it's possible to disable scanning if you want to program for training just with relay logic, I mean without the need for OSR function. I know that you're an expert in it, so that's why I'm asking someone like you. Thanks.

@TimWilborne 3 жыл бұрын

Yes, absolutely

@iliapopovich 3 жыл бұрын

@@TimWilborne Thanks for the answer. I understand you're joking, but for example, the first scan reset doesn't work obviously. So actually I need to disable any machine scans during the process.

@ryanconnigrizzard1647 4 жыл бұрын

Hey Tim, Amber. Im having a problem with my AB micro 1200 plc's. I notice that they are starting to go into "watchdog timeout fault". I can clear them but they come back. First time i clear them it would work for a week. Second time it would work for a day or two. Now after about 8 clears it faults within an hour. Any ideas on fixing this?

@TimWilborne 4 жыл бұрын

What that means is that your PLC scan is occasionally too long. This could be caused by a very long program or excessive program loops using JSRs. While online, click on the S2 data file and you can see what the current scan time is, the maximum, and what the watchdog is currently set at.

@ryanconnigrizzard1647 4 жыл бұрын

@@TimWilborne thank you, ill try that. Program is very short. 1 analog device only.

@TimWilborne 4 жыл бұрын

@@ryanconnigrizzard1647 Email it to me and I'll have a look.