stop/start with same PB

shane Smit · Nov 22, 2003

Can enyone help me with this?
I want to make a Stop/Start program using the same pushbutton but, the
big catch is I can only use two lines. I can get it work only a few
times in a row but I cant figure out the exact scan times. Oh ya, I can only use contacts and coils not tools.

Thanx.

Steve Bailey · Nov 22, 2003

Do a search of this forum using the keyword 'flip-flop'. The topic has been discussed many times.

93lt1 · Nov 22, 2003

Shane Smit different day...

ArikBY · Nov 22, 2003

I hope that will help you
202.00 set one shot on 201.00 which start and stop 203.01

Eric Nelson · Nov 22, 2003

Arik, the 'traditional' flip-flop is like this:



|   INPUT                  ONE-SHOT

|----] [---------------------(  )

|

|  ONE-SHOT    OUTPUT       OUTPUT

|----] [---------]/[-----+---(  )

|                        |

|  OUTPUT      ONE-SHOT  |

|----] [---------]/[-----+

Yet you have:



|   INPUT                  ONE-SHOT

|----] [---------------------(  )

|

|  ONE-SHOT^   ONE-SHOT^    OUTPUT

|----] [----+----]/[-----+---(  )

|           |            |

|  OUTPUT   |  OUTPUT    |

|----] [----+----]/[-----+

Which will work, but the toggle to OFF looks like it will be delayed one scan. I understand that you HAVE TO use a transitional contact with the normally-closed contact in order to make your logic work, but why do you need it with the normally-open contact, when 201.00 is already transitional?

Just curious?...

beerchug

-Eric

Antipathy · Nov 22, 2003

Shane said:

I can only use two lines

If by this you mean 2 rungs of ladder logic then Arik's or Eric's methods are fine.

If on the other hand you literally mean 2 lines using ladder logic, then as far as I know your particular PLC has to have a built in flip-flop instruction (i.e. Mitsubishi's ALT).
Of course you would still need to use a one-shot (ONS-AB, DIFU-Omron, PLS-Mitsi). Otherwise the instruction would operate on every scan of the PLC, leading to rapid alternation of the output whilst the input is on.

|   INPUT                  ONE-SHOT

|----] [---------------------(  )

|

|  ONE-SHOT         FLIP-FLOP (ALT) OUTPUT

|----] [---------------------(  )

|

One complication that many programmers overlook is shaky hand syndrome or dodgy contacts which can lead to input bounce and consequent unexpected results (from pressing the button). I use a timer to help avoid this problem...

|   INPUT           TIMER              ONE-SHOT

|----] [-------------] [-----------------(  )

|

|  ONE-SHOT         FLIP-FLOP (ALT) OUTPUT

|----] [---------------------(  )

|

|  ONE-SHOT                 TIMER

|----]/[--------------------(0.2s)

Anthony

Antipathy · Nov 23, 2003

Anyone spot the mistake?

I posted last night from memory and after looking at it today I spotted a glaring error on the second ladder!

It should have read:



|   INPUT           TIMER              ONE-SHOT

|----] [-------------] [-----------------(  )

|

|  ONE-SHOT         FLIP-FLOP (ALT) OUTPUT

|----] [---------------------(  )

|

|   INPUT                    TIMER

|----]/[--------------------(0.2s)

As previously posted it would have alternated the output every 0.2 seconds...

However, having studied the ladder further, I think this would work:



|   INPUT           TIMER       FLIP-FLOP (ALT) OUTPUT

|----] [-------------] [-----------------(  )

|

|   INPUT                   TIMER

|----]/[--------------------(0.2s)

That's two lines of ladder and an input buffer timer!

Anthony

ArikBY · Nov 23, 2003

Eric F
Far as I remember that the way it work with Omron.I use this way
so maney years and i dont remember why.
In AB I use the "traditional" way and it work fine.
I will check it again and let you know.
Thanx for your comment.

Anthony
If we had in our PLC alterant contact we would not have this discussion, if you have built in altrant contact you dont need the timer just the input output(alterant contact) and one shot.

Mike6158 · Nov 23, 2003

Interesting

None of the examples shown will work in a Siemens TI555. It takes 4 rungs in the 555. I wrote a small SCL file for the S7 to do it with a block. This was used to allow one button on an operator interface to toggle a PID loop between auto and manual but the prinicpal is the same. The code looks like this-

FUNCTION_BLOCK FB106

TITLE = 'Auto/Man Toggle'
//
// AUTO/MANUAL TOGGLE FOR PID Loops
//
VERSION: '1.0'
AUTHOR: MLL
NAME: AUTO_MAN
FAMILY: OP17

VAR_INPUT

// Output Parameters

AUTO_MAN_INPUT : BOOL;

END_VAR

VAR

CURRENT_STATE : BOOL;

END_VAR

VAR_OUTPUT

// Output Parameters

AUTO_MAN_OUTPUT : BOOL;

END_VAR

BEGIN

IF AUTO_MAN_INPUT AND Current_State THEN
AUTO_MAN_OUTPUT := FALSE;

END_IF;

IF AUTO_MAN_INPUT AND NOT CURRENT_STATE THEN
AUTO_MAN_OUTPUT := TRUE;

END_IF;

Current_State := AUTO_MAN_OUTPUT;

END_FUNCTION_BLOCKO

Mike6158 · Nov 23, 2003

And in STL

You can also do a toggle in Statement list-

A DB9.DBX 4.0
FP M 11.0
= L 0.0
A L 0.0
AN DB9.DBX 0.0
S DB9.DBX 0.0
A L 0.0
A DB9.DBX 0.0
R DB9.DBX 0.0

Antipathy · Nov 23, 2003

Arik

No offence mate, but did you actually read my first post?

Since the originator of this thread (Shane) didn't state which PLC he needed to code to and given that he also wanted the code in two lines (he wrote 'lines' and not 'rungs') I stated that he can only do this if his PLC has an ALTERNATE (flip-flop) instruction:
I wrote:

your particular PLC has to have a built in flip-flop instruction (i.e. Mitsubishi's ALT).

You wrote:

if you have built in altrant contact you dont need the timer just the input output(alterant contact) and one shot

Do you mean like the first ladder shown in my first post?
Once again, I refer you to my first post:

One complication that many programmers overlook is shaky hand syndrome or dodgy contacts which can lead to input bounce and consequent unexpected results (from pressing the button)

Clearly, a one-shot and a flip-flop will work... The timer part just improves the reliabilty and if it is implemented as I have shown in the final ladder, it will eliminate the need for a one-shot. Because, in effect, the timers output bit can only be on for one scan when the input button is pressed.

Anthony

ArikBY · Nov 23, 2003

Eric the F is typing mistake sorry.

Anthony

First I want to apologize I didn’t mean to harm or insult.
I assumed he(Shan) didn’t have alternant contact on his PLC.
With alternate contact you still need 2 rungs .If Shan mean 2 line it maybe in STL Your way show also 2 rungs.
Your ladder. The timer is not necessary, it work like one shot and not give any thing just delay between the button hits (I hope I write it right).
Because after you hit the button the one shot(or output) go on and the timer go off.
It happen in one cycle.

rsdoran · Nov 23, 2003

How can somthing so common be debated?

I dont know about TI550 but the S7 has a toggle

rsdoran · Nov 23, 2003

nevermind

hesham · Nov 24, 2003

Do As Steve told you Search the site .
See this thread for example
thanks

stop/start with same PB

shane Smit

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Steve Bailey

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93lt1

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ArikBY

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Eric Nelson

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Antipathy

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Antipathy

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ArikBY

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Mike6158

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Mike6158

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Antipathy

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ArikBY

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rsdoran

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rsdoran

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hesham

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