Hand/Off/Auto logic RSLogix?

[tomalt]

I guess I need a idea what you guy's mean by "Hand" "Auto" and "OFF" to give any real input.

We usually talk Auto/Manual and sometimes Step mode.

 

[Mickey]

I guess I need a idea what you guy's mean by "Hand" "Auto" and "OFF" to give any real input.

We usually talk Auto/Manual and sometimes Step mode.

Hand/Off/Auto is a throw back to hardwire systems
See site below

http://www.exman.com/mshoa.html

 

[OkiePC]

I think the OP used duplicate OTE instructions with the same addresses.

Someone earlier said the first one wins, well I believe that is mistaken. The last one would win.

Since there are 3 MODES (whatever you want to call them), you need at least two bits to represent all three uniquely, whether hardwired or in a CPU.

We have a new mode here that made me laugh: Instead of semi-auto, they call it "semi-manual". Hard to change factory floor terminology sometimes...

Hand means manual, and in hard wired ciruits was usually a selctor switch. Auto, meant just that, Hand, gave you certain jog button controls.

Sometimes we used 3 position spring return from one side only (center and right maintained operator) and called it "Jog" "Off" "Auto" so a single button enclosure gave you all those features with one simple gloved hand operator. Jog was momentary and to the left no matter which conveyor you were working with...very efficient design.

Some even were keyed and, at that time, qualified as lockout points for mechanical maintenance. I don't think that is still the case.

IMHO in a PLC: Off should be no bits, Hand is a bit, and Auto is a separate bit. Write your logic so that comms failures clears both bits, and keep them as maintained or momentary in the PV but either way, unlatch (reset, OTU) them in the PLC once they are detected and used in a seal in rung in the PLC.

An OTL or OTU instruction when evaluated as false will not change the state of the address, and MAY be duplicated in A/B PLCs, but never do it with an OTE output coil, because they always write the state of the rung to the address, even when false.

Your branching logic with one output should have worked.

Use ALT+PrntScrn to capture the RSLogix window, paste it in MSPaint, trim off the unnecsarry edges so it fits in the requirements here, and save it as a JPG with no whitespace in the filename.

Then, at the bottom of the reply window, look for Display Pictures button, and follow it from there.

It will open an upload utility which will require you to paste the finished file path and name back into your post text as a link.

Once you learn that little visual aid tool, your posts become thousands and thousands of words, with a few mouse clicks...

The qulity of the generated solutions and your learning will grow exponentially as well.

 

[tomalt]

This is how I would try first.

 

[optimus2861]

He's saying that the idea was a bad one.

Why? I don't understand the blunt criticism of the idea myself; I've never had an operator balk at Auto/Manual, Start/Stop as two seperate sets of HMI buttons, with Start/Stop only visible when in manual.

 

[Norml]

Hand/Off/Auto is a throw back to hardwire systems
See site below

http://www.exman.com/mshoa.html

Local Off Remote is all the rage with our biggest customer.

 

[cntrlfrk]

Why? I don't understand the blunt criticism of the idea myself; I've never had an operator balk at Auto/Manual, Start/Stop as two seperate sets of HMI buttons, with Start/Stop only visible when in manual.

I think it depends on what you are used to. In my opinion, the "H" in HOA is the same as an ON button, because that is all it does. So you basically want an On, Off, and Auto selection. But the way a physical HOA is installed and wired in the plant, you cannot, and should not be able to select the On or Off while you are in Auto, so making that button invisible keeps people from toggling a button they think is affecting something when it doesn't. Your transition from MAN->AUTO and back can be done however you want in logic.

But, then again, I've never claimed to know it all either...

 

[dogleg43]

RE:
**************************
Why would you use 2 separate bits for Hand and Auto? I would just have one button toggle a bit (Hand/Auto) and another button toggle a bit(On/Off) and make the On/Off button only visible when the Hand/Auto button is in Hand.
**************************

You might want to check the codes and specification you are required to follow. Many require 2-steps to go place a machine into the "Auto" mode, thus the "OFF" or "RESET" mode.

 

[rsdoran]

Just an old chihuahua barking at the heels of the big dogs

HOA
H means HAND ie manual, as in do it by hand.
O means OFF, if do not understand that nothing I can say will matter.
A means automatic ie the machine runs by itself once started.

NONE of these should initiate the cycle.

NONE of these alone should control any specific output.

 

[TConnolly]

The potential problem is see is this:

Operation is in Auto. Hidden manual switch is in OFF. Operator does not know this because the switch is not visible. The operator needs to switch it to Hand (Manual ON) without interrupting the process. So he first activates the manual mode. Then the ON/OFF switch becomes visible and operator realizes that it is OFF so he then has to turn the switch on. Meanwhile, the conveyor or pump or whatever turned off and the operator uses an expletive. Boss is p.o.-ed because production or process is interrupted. Operator gets blamed for something he was not given the tools to properly deal with. The opererator then calls the equipment you designed a piece of excrement and persistently believes his description to be accurate, no matter how many other well working cool features it has.

The reverse scenario is just as likely and also potentially troublesome; operator wants to swtich to Manual OFF but unknown to opererator, invisible ON/OFF switch is ON.

With three buttons to select HAND-OFF-AUTO mode the operator can do what he needs to do. He can go from AUTO to HAND(ON) without interrupting the process. He can also go directly to OFF without waiting for an invisible switch to become visible. The machine is predictable to the operator and even if its not loaded with cool features, its like an old dependable familiar tool to him.

 

[bernie_carlton]

rsdoran seems to be referring to a HOA switch which controls the entire machine operation. Alaric, and others, seem to be referring to a seperate HOA switch for EACH OUTPUT.

 

[TConnolly]

I'm refering to is as a mode for a particular function, be it a single output or a series of outputs.

 

[rsdoran]

rsdoran seems to be referring to a HOA switch which controls the entire machine operation. Alaric, and others, seem to be referring to a seperate HOA switch for EACH OUTPUT.

Why would you have an HOA for each output?

Pardon me, had a couple, but these are still my thoughts. I will attempt to address them in better detail tomorrow.

 

[TConnolly]

As an example, I've done a few cooling towers. There is typically an HOA switch for each pump and each fan in the system.
It depends entirely on the function of the output and the required control for the connected device. Thats why I specified that I was refering to functions, not outputs.

 

[rsdoran]

I can see it will not matter, so I will not address this in more detail.