One Push Button: Please Please explain clearly

[OkiePC]

One Push Button: Please Please explain clearly

I have seen many posts regarding start and stop using one push button but no one has explained what he is trying to do.

Uhh, I think that would be stop and start something.

Please whenever you write code explain step by step what are you are doing. so people like me who just started learning plc will know what you guys are doing.
Please explain me how to use one push button as start and stop. Thanks

Well, the way you do that, is understand the functions available to your controller, and decide which one will work. If it is too complicated or you need a fresh idea, look for examples on the internet and apply theses along with your understanding of the goal of your program and the machinery you're controlling to achieve the desired result.

Stop and start what?

You want an exact answer? I gave the most exacting one possible based on your vague question.

Stop and start what?
How?
With what?

 

[Riche Robledo]

Thanks for your reply. Now i learn what is the logic behind this. Can you please explain me how to write the code.

I understand what you are felling friend! You want to know the start stop using a single push button??? The logic is you have to use a 3 relays.

Please try ,If you press the push button, first relay will turn ON momentarily and it give signal to the third relay to turn ON even the push button is released.The auxiliary of this third relay holding the contact so that it will remain ON.
You got it!! The first logic?

Since the first relay is OFF and the third relay is ON,

A normally close contact of second relay is in series of third relay.
When you press the push button again,the current should not go to the first relay because of normally close contact of third relay is opened.

The current should go to the second relay it give turn OFF to the third relay.

(A contact of first,second and third relay will make harder to you to interlock this circuit)but you have to understand the sequence...good luck..

RR

 

[John Gaunt]

To be practical about this:
Use a two position STOPPED / RUN switch (90 degree rotating) rather than a push button. Still only one PLC input and understandable for the operator.
Alternatively use a mechanically latching push button but I much prefer the rotating 2 position switch.

Either of the above can benefit from indicator lights that can be low cost 24 Volt DC LED.

 

[Craig Spinharney]

On/Off Toggling of one or more bits.

I use to challenge my students to see who could come up with a toggle operation for 1 or more outputs in the least amount of rungs/instructions.
Best I was ever able to do was 3 instructions on 1 rung or 2 instructions on 1 rung with a DII/PII/Event task.
Most students would wind up using 2-4 rungs and about 7-12 instructions.
It was a good programming exercise.

 

[adfox]

jamalshahid
Is it so hard to figure it out ?

A PushButton
Fp aux
= PushButton_Pos

A PushButton_Pos
AN State_ON
S State_ON

A PushButton_Pos
A State_ON
R State_ON

 

[iant]

To be practical about this:
Use a two position STOPPED / RUN switch (90 degree rotating) rather than a push button. Still only one PLC input and understandable for the operator.
Alternatively use a mechanically latching push button but I much prefer the rotating 2 position switch.

Either of the above can benefit from indicator lights that can be low cost 24 Volt DC LED.

Sorry John - You have missed the point of the excercise.
I recommend you try this program

a selector is great BUT
Can you change it's state with a program step or via touch screen?
to either On Or Off.
this logic is used in many applications and Often selector switches are too costly.

 

[krk]

A PushButton
Fp aux
= PushButton_Pos

A PushButton_Pos
AN State_ON
S State_ON

A PushButton_Pos
A State_ON
R State_ON

Got this on here from 'S7Guy' back in '07.......

A  PushButton
FP aux
X  State_ON
=  State_ON

 

[TConnolly]

One of our forum members, Doug_P has an animated avatar that shows a simple flip flop that will work with most PLCs.

This flip flop can be programmed on pretty much all PLCs. Assuming P is an unbuffered push button input it cannot be guaranteed to always work on a ControlLogix platform - most of the time it will work but there could be instances when the CLX IO updates between the first and second rung of Doug's flip flop.
[/quote]

 

[IJK]

single shot logic

Check the screen shot

 

[iant]

Different PLC's can handle this different ways
"IJK"
Omron do almost the same with a Keep Relay

"AlAric" is the probably the best method for most PLC's

PLC Scan times and bit handeling times can effect that process

 

[BSS@ADPS]

Yeah, i totally agree with you programming is hard but i am unable to understand how to start writing codes. Some times i know the logic but when i start writing programs i am unable to figure out what to do.

Hi, Is it just me...?
when i have trouble getting started on a project..... i´ll use paper and a pencil or am i just old school?

 

[adfox]

Hi, Is it just me...?
when i have trouble getting started on a project..... i´ll use paper and a pencil or am i just old school?

I use pencil and paper with every task, it's easier to organize or keep TODO list updated.
Also I always carry large notepad while working in the field- it's just easier to organize thoughts and have a plan before my eyes.

 

[paraffin power]

jamalshahid
Is it so hard to figure it out ?

A PushButton
Fp aux
= PushButton_Pos

A PushButton_Pos
AN State_ON
S State_ON

A PushButton_Pos
A State_ON
R State_ON

You're right; it is easy to figure it out. So you probably shouldn't post incorrect code. I'm just saying...

 

[coolasad14]

Sample Code - Ladder

This logic is developed for momentary push button. FYI safety systems does should not use this On-Off Logic.

 

[IJK]

sorry for the incomplete info.

actually i have done this logic in Siemens step 7

and it work for sure