This just HAS to be easier than I'm making it...

[afoley]

I need to convert a pulsing (off,off,off,on,off,off,off,...etc.) signal to a steady on or off input to an allen bradley PLC/5. if the pulse stops,(either on or off) I need to reverse the state of that imput. (If any of you are in the mining industry, think about a slip/sequence switch, without the BWI Eagle.)
I can do this, BUT, when I look at the resulting ladder, and consider that a first year maintenance guy will have to troubleshoot it, I do not want to get called at three in the morning to explain ladder logic.
Whoever shows me the simplest way to program this, I will name my next son after them.
PS:
I am 50 years old and recently divorced from the third wife so, in all likelihood, you will be doing this exersize for the pure enjoyment of it, not any resulant legacy.

 

[tom_stalcup]

Let's see if I understand what you are wanting....

You need a flip-flop setup on an output, that only changes state when the pulse input stops pulsing?

 

[afoley]

Close, I need the flip flop on an input. converted to a binary on or off if it keeps flip flopping, then to a binary on or off if it stops flip flopping.

As the first reponder, the kid gets your middle name.

 

[tom_stalcup]

Hmm... I'm a little dense sometimes, so lets go with something a little more structured:

State 1:
input is pulsing, output is following the pulse? on,off,on, off, etc.

State 2:
Inputs stops pulsing HIGH... Output needs to be OFF??

State 3:
Input stops pulsing LOW... Output needs to be ON??

Or am i missing something (again)...

 

[tom_stalcup]

or are you looking more at something like this:

State 1: input is PULSING, output is ON

State 2: input stopped PULSING, output is OFF

 

[bernie_carlton]

The input to the AB may be pulsing or not.

First of all, you need to differentiate, both ways, the signal. If the PLC5 has bot an one shot rising and a one shot falling you are in luck. Let's say that it does. You now have signals "turn-on" and "turn-off".

Make an AND of the NOT of each one shot. "If NOT "turn-on" AND NOT "turn-off" then enable a timer. The preset of the timer is amount of time without a transition that you will consider the input "stopped". So the DN output of the timer is "stopped"

Now I'm confused at this point. I think you said, each time the signal stops, toggle another signal ("toggled output"). If that is right then just one-shot the "stopped" signal. Call this "just stopped".

So another rung has : If ("just stopped" and NOT "toggled output") OR (NOT "Just stopped" and "toggled output) then turn on "toggled Output" (This is the classical form of the student's "create a flip-flop without etc.)

I probably messed up your definition somewhere but a glimmer of an idea should be in there somewhere.

 

[Steve Bailey]

Two timers. One enabled by the the OFF state of the input, the other by the ON state. Timer presets are longer than the normal ON and OFF times of the pulsing input.

If both timer's done bits are off, latch a bit ON. If either timer's done bits are on, unlatch the same bit. The ON state of that bit indicates that the input is pulsing. The OFF state indicates that the input has stopped pulsing.

 

[elevmike]

PS:
I am 50 years old and recently divorced from the third wife so, in all likelihood, you will be doing this exersize for the pure enjoyment of it, not any resulant legacy.

Never say never......

The only question I have is the timimg of the pulses. How long of a on or off would trigger the output?

 

[Doug_Adam]

What about use a pair of delay off timers and AND their outputs.

NO pulse input feeds into T1 (Delay off).
NC pulse input feeds into T2 (Delay off).

Preset times for both timers are set to be higher than the known period of the pulse train.

The two outputs are then seriesed in a rung for your output.

While the pulse is changing, both timer outputs are on.

When the pulse stops, either on or off, one timer output will be on and one off (after the timeout).

Overall result, when pulse is pulsing, your output is ON, when it stops, you output switches OFF after a short delay.

EDIT NOTE - looks like Steve beat me to it

 

[elevmike]

I need to convert a pulsing (off,off,off,on,off,off,off,...etc.) signal to a steady on or off input to an allen bradley PLC/5.
If the pulse stops,(either on or off) I need to reverse the state of that imput.

I need the flip flop on an input. converted to a binary on or off if it keeps flip flopping, then to a binary on or off if it stops flip flopping.

Hmmm...

Do you want the output "off" or "on" if the input is pulsing? (Pick one only)

Do you want the output "off" or "on" if the input stops pulsing? (pick one only)

BTW, time to get a dog. Cheap to feed & clothe, ALWAYS happy to see you, NEVER gossips, Dosnt watch QVC, and rarely talks back.

 

[afoley]

As I said, I can do this, but my solution requires two timers, and some logic...thus three rungs minimum, plus each rung has at least one branch down....As do all that I have seen here so far.
Can you come up with someting that Bubba on third shift can understand?

Come on guys, you know you want a future controls guy sporting you name.....

 

[afoley]

What about use a pair of delay off timers and AND their outputs.

NO pulse input feeds into T1 (Delay off).
NC pulse input feeds into T2 (Delay off).

Preset times for both timers are set to be higher than the known period of the pulse train.

The two outputs are then seriesed in a rung for your output.

While the pulse is changing, both timer outputs are on.

When the pulse stops, either on or off, one timer output will be on and one off (after the timeout).

Overall result, when pulse is pulsing, your output is ON, when it stops, you output switches OFF after a short delay.

EDIT NOTE - looks like Steve beat me to it

It looks like you and Steve have reproduced my logic....I was hoping for something easier for the "third shift guy" to follow.

 

[afoley]

Sorry Doug, I didn't mean to overlook you, you got the same solution....

 

[afoley]

The input to the AB may be pulsing or not.

First of all, you need to differentiate, both ways, the signal. If the PLC5 has bot an one shot rising and a one shot falling you are in luck. Let's say that it does. You now have signals "turn-on" and "turn-off".

Make an AND of the NOT of each one shot. "If NOT "turn-on" AND NOT "turn-off" then enable a timer. The preset of the timer is amount of time without a transition that you will consider the input "stopped". So the DN output of the timer is "stopped"

Now I'm confused at this point. I think you said, each time the signal stops, toggle another signal ("toggled output"). If that is right then just one-shot the "stopped" signal. Call this "just stopped".

So another rung has : If ("just stopped" and NOT "toggled output") OR (NOT "Just stopped" and "toggled output) then turn on "toggled Output" (This is the classical form of the student's "create a flip-flop without etc.)

I probably messed up your definition somewhere but a glimmer of an idea should be in there somewhere.

Bernie...
I have to work on this thought a while...
No offense intended, but is English not your native language?
Again, please, no offense intended.

 

[afoley]

Tom,
No, not quite.
Input is pulsing, output is ON,
Input not pulsing, output is OFF.