Single button Start Stop latching logic

Does anyone have a sample of logic using one button to start and the same button to stop an output. I am trying to do this in RSLogix 500 and due to the scan time, the method of programming I am trying to use isn't working. Just looking for some thoughts as I need to step back from this.

Thanks!

Does anyone have a sample of logic using one button to start and the same button to stop an output.

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Yep.

to the scan time the method of programming I am trying to use isn't working

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You reckon? You could slow your scan time down to 2 seconds ( if that is possible ), and then your solution may work. But then every thing else will be too slow responding.


Humuor aside, do a search for flip-flop, jk or the like. There is also another thread about 'WAS' bits, this may help also.

I am trying to do this in RSLogix 500 and due to the scan time, the method of programming I am trying to use isn't working.

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This will work, but scan time can not be over 35 seconds?
http://www.plctalk.net/qanda/attachment.php?attachmentid=6917&stc=1
Sorry couldn`t help it!

I0/0 . . . .B3/1. . . B3/0
----| |------|/|--------(L)

I0/0 . . . . . . . . . B3/1
----| |-----------------( )

B3/0 . . .O 1/0 . . . O 1/0
----| |----|/|----------(L)
. . . . . . . . . .|
. . . . . . . . . .| B3/0
. . . . . . . . . .+-----(U)

B3/0 . . . O 1/0 . . . O1/0
---| |-----| |----------(U)
. . . . . . . . . .|
. . . . . . . . . .| B3/0
. . . . . . . . . .+-----(U)

This should work, When I0/0 goes on it sets B0/0 It also = B3/1 so B3/0 cannot set again while button is pressed, this sets O1/0
& resets B3/0 but cannot reset B3/0 on any futher scan as O 1/0 is on
As B3/0 is reset on set of O 1/0 this cannot reset O 1/0
If button is released B3/1 is off but on the button I 0/0 being pressed again & the last rung is true reseting O 1/0
you could use the oneshot bit in slc but I showed standard logic for this purpose
If you used mitsubishi there is an alt command that sets a bit on rising pulse then resets it again on next rising pulse

Stealing parky's ladder - only reference the input once.

I0/0 . . . .B3/1. . . B3/0

----| |---+--|/|--------( )

          |

          |. . . . . . B3/1

          +-------------( )

 

 B3/0       O:1/0     O:1/0

--| |--------|/|---+---( )

                   |

 B3/0       O:1/0  |

--|/|--------| |---+

Stealing parky's ladder - only reference the input once.

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Also, you have avoided using Latch/UnLatch instructions, and have created your own 1-shot. The way to go, some PLC's may not have
a true 1-shot.....

XIC Button CTU C5:0 10 0
XIC C5:0.acc/0 OTE Output

Works well but retains it's state I think (its a while since I used it)

scottmurphy said:

Also, you have avoided using Latch/UnLatch instructions, and have created your own 1-shot. The way to go, some PLC's may not have
a true 1-shot.....

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sssshhhh... he stole the rest from me but who's keeping score..:nodi:

scottmurphy said:

Also, you have avoided using Latch/UnLatch instructions, and have created your own 1-shot. The way to go, some PLC's may not have
a true 1-shot.....

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I am not so sure that Latch/Unlatch, SET/RESET, or any available instructions should not be used.

Not sure exactly what a true one-shot is, maybe someone could define it. I do understand it is more desireable to have it trigger rising edge.

That said AB has ONS or OSR, AD has PD (positive differential), Simatic S7 (maybe S5 too) offers a PD (I think an ND too), GE has POSCOIL and NEGCOIL, Simatic/TI Softshop has a one-shot that uses the # sign. Unitronics has -}P|- positive edge transition. Those are the programs I have on this desktop, my laptop has more but think all them have some form of positive edge triggered contact or coil that is only on for one scan.

S7-200 has a toggle function.

The instruction may not be called one shot, it may be differential, transition, positive edge and may be a contact or a coil.

Since we are on the subject what brand(s) do(es) not have a one shot?

May start a thread about using latch/unlatch, five years ago there is no way I liked them but things change and not sure there is no reason they should not be used.

rsdoran said:

Not sure exactly what a true one-shot is, maybe someone could define it.

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A one shot is usually accepted as something that is high for 1 scan only. Rising or Falling edge, whichever you want (S5 never had one, so S7 has two just to be flash).

one shots and latches have their uses and are a major pain in the @rse when they are abused.

Nothing worse than the timing issues you can get when someone falls in love with one shots.

I am not so sure that Latch/Unlatch, SET/RESET, or any available instructions should not be used.

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Neither, except in this application, are they really needed?

Not sure exactly what a true one-shot is

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I used a small PLC (programmable relay infact) recently, and I thought that it only had a pulse instruction, but have jsut double checked, and it does have a one-shot.

One shots and latches have their uses and are a major pain in the @rse when they are abused.

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I use them also, but when they are required. If I can avoid them I will, unless there is an absolute need, and there are plenty of cases in some of my projects where I use them

re:




Politly this must be the world's shortest 1 button on-off lad. code!

This is the smartest code i ever done, i used in seweral applications and newer failed or timeouted...

But it uses 17bits instead of I/O's..

Savaş; (Thx. M. Emin Dinc)

Here is a simple one I have been using with Clx. One thing I would do using a physical button is use a very small debounce timer.

Thanks to all...

I appreciate everyones input...I knew that there were a variety of ways to do this and according to the posts, there are quite a few.
Again...thanks a bunch.