It's like a hidden parameter

Reizeik · Dec 1, 2016

Please help me answer this PLC Programming problem.

Problem 1.

When Start Push Button is pressed, Motor is going to start. When Stop Push Button is pressed Motor will stop, but the START Pushbutton (I0.0) and the STOP Pushbutton (I0.1) are not included in the program in any POU (Main, Subroutine, Interrupt).

I/O ADDRESS ASSIGNMENT:
I0.0 ----------- START P.B
I0.1 ----------- STOP P.B
Q0.0 ----------- MOTOR

If you may, can you please send a ladder program if you have a possible answer? That would be a great help for a newbie like me.
Thank you experts for your kind reply.

bright676 · Dec 1, 2016

What is the question?

labeledas · Dec 1, 2016

Is Q0.0 turning on, or do the start and stop PB control a latching relay circuit that is controlling the motor and not the PLC.

Reizeik · Dec 1, 2016

The question Sir is how to program that you can turn on/off output Q0.0 by flipping switches I0.0 and I0.1 without finding the switches in the program?

gclshortt · Dec 1, 2016

Use a compare on the input channel to see if the bits are on or off.

Regards,

labeledas · Dec 1, 2016

magic I guess, or force Q0.0 on when someone flips switch.

Is this a school exercise cause it doesn't make much sense

Reizeik · Dec 1, 2016

labeledas said:
Is Q0.0 turning on, or do the start and stop PB control a latching relay circuit that is controlling the motor and not the PLC.

I don't really understand the terms you are using Sir but it is like when you on the switches I0.0 and I0.1 it turns Q0.0 on and off, so basically it turns the machine on and off but without the parameters I0.0 and I0.1 in the program. So it's like the switch will control the machine directly.

Reizeik · Dec 1, 2016

gclshortt said:
Use a compare on the input channel to see if the bits are on or off.

Regards,

I'm not really sure how to do that. So if you may Sir, can you send me an image of its ladder program?

Reizeik · Dec 1, 2016

labeledas said:
magic I guess, or force Q0.0 on when someone flips switch.

Is this a school exercise cause it doesn't make much sense

Yes Sir, it's a pre given final exam review question and our instructor assures us that this question will come out on the exam.

labeledas · Dec 1, 2016

do you actually see Q0.0 turning on and off what is in the PLC program now, what inputs come on when you hit the start button.

is this a working system?

bjh · Dec 1, 2016

Is this an exercise that is trying to teach you to use aliases/references to the physical I/O?

For example. instead of using I0.0 directly on a contact, create a boolean variable called "StartPB" that is aliased to I0.0 etc.

Reizeik · Dec 1, 2016

labeledas said:
do you actually see Q0.0 turning on and off what is in the PLC program now, what inputs come on when you hit the start button.

is this a working system?

I think so that this is a working system, Sir. Our instructor is a well-known trainer in PLC programming, he even coached students in the recent 2016 ASEAN Skills competition in Malaysia and they won a gold medal.

So much for that, yes, it is required that Q0.0 will turn on and off on the PLC when switches I0.0 and I0.1 is flipped

AustralIan · Dec 1, 2016

I think this is a textbook problem rather than a "can I please have more information."

There can be several reasons for this, particularly as the PLC brand was not clearly stated. The most obvious solutions are indexed addressing or referencing the entire byte, word or double word with a mask.

Reizeik · Dec 1, 2016

labeledas said:
do you actually see Q0.0 turning on and off what is in the PLC program now, what inputs come on when you hit the start button.

is this a working system?

bjh said:
Is this an exercise that is trying to teach you to use aliases/references to the physical I/O?

For example. instead of using I0.0 directly on a contact, create a boolean variable called "StartPB" that is aliased to I0.0 etc.

I think that's a good idea, Sir. Our instructor never gave us many hints for this. He just said that "I0.0" "I0.1" should not be seen in main subroutine and interrupt but switches still functions the same.

Reizeik · Dec 1, 2016

bjh said:
Is this an exercise that is trying to teach you to use aliases/references to the physical I/O?

For example. instead of using I0.0 directly on a contact, create a boolean variable called "StartPB" that is aliased to I0.0 etc.

If you may Sir, can you please send me a ladder program for your solution? That would be a great help for a newbie like me.

It's like a hidden parameter

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