Connectivity between MicroLogix 1000 and PanelView C600

[iant]

Depending on you Safety requirements.
there are many posts about this - please search seperately.

the E/stop Input, into your PLC should perform two functions - this should be an Auxillary contact - Preferably from a safety relay.
1. to stop the PLC Internal processes
- motors - cycle - or what ever else the PLC controls
2. an Indication to the PLC that an E/Stop has been pressed.

the safety should operate seperately and not be dependant on the PLC changing state of outputs

your 'L1 as well?' query can not be answered correctly - sorry

 

[SergioB]

I now see what you mean by having a physical contact update an internal address bit (shown below).

Sorry about my ladder example. I did not correctly implement what Paul explained earlier. It was late and was on my way out and did not have time to make the changes. Please disregard that screenshot.

Thanks for the explanation Ian! I will also review the previous safety requirement posts separately.
sb

 

[OkiePC]

Now, regarding your comments about the "emergency" stop button, I'm still not sure I completely understand what you mean. Are you saying is not used because of the type of PLC I'm using? Or is it a general comment about how an emergency button should not be wired as an input only, but instead be hard-wired directly to L1 as well?

Thanks!!!
sb

General comment about how a true e-stop should be hardwired, and that it is bad practice in my opinion to use the term e-stop to describe anything less.

Mainly, I want to drive home the point that you should always consider a circuit that is subject to software interpretation less than suitable for e-stop. Also, few PLCs are rated for safety applications. You will know if you ever encounter one.

It is only a comment, a piece of text no one else may ever see...In the future, you may create logic that survives for decades including your comments so take words like e-stop very seriously.

I don't know whether your application needs an e-stop, so just call it stop.

I like my comments to follow a format that includes the device type, then short name, then contact type or style:

PB Stop
Maintained

or

PE Door
Entry
Light Operated

When you start sorting through lists of hundreds or thousands of comments you will quickly see how having a structure for symbol names and even comments is a wise investment in planning. You can see that if all of your photocells begin with PE or PC, how easily you can alphabetically sort them to get them all in one area of a list. Some folks like to begin with a station name or number for large machines, so if you only want to look at Load Station A" I/O it is easy to sort.

Paul

 

[SergioB]

Got it!

Regarding proper references/names in comments, is there a 'standard'? In programming, one can find coding standards for different types of programming languages. Is there such a thing for proper naming things in ladder logic comments?

Thanks,
sb

 

[iant]

there are many options
we try to name something for what it is.
the Idea of E/stop compared to a 'Stop' is generally two different terms.
E/Stop - (I Know ther are differing oppinions) means stop and prevent ALL
motive / electrical / pneumatic / hydraulic (stored energy) from functioning in any way.
- IF you force a PLC output or electrically bridge it out - the E/stop should ignore that bridge. - Prevent all operation posibilities.
Guard systems are similar.


where as a - STOP is only that - (your RISK ANALYSIS) - says it doesnt matter if you bridge it OR does it
- YOU need to ask if this is true - we can not tell you that.

At the end of the day
What is the operator of a machine going to press first in an emergency.
How do you Know it will work????
How do you confirm it works.????
AND - CAT. 4 level Safety
----- HOW do you confirm that the confirm has worked.????
----- Before it cycles -----
(What checks the checker?)

 

[SergioB]

Excellent points Ian.

Will definitively invest time learning these safety aspects.

Thanks,
sb