Toggle to Momentary?

Here's an interesting one.

We have a device that has a PB which can only function in toggle mode.
i.e. you press & release it once and the output goes on, then you press & release it again and the output goes off.

We want to use this pushbutton as a pseudo-momentary PB. I think the best we can do is to get a timed pulse out of it. The PLC is a Moeller Easy 800 which I'm still not very familiar with but my plan is to catch the leading and trailing edges of the output and generate a timed pulse when either of these occur. something like:

   PB                 rising

---] [-----[osr]--------( )





   PB                 falling

---]/[-----[osr]--------( )



 rising        Pulse/DN     Pulse

---] [---+--------]/[-------(TON)

         |

falling  |

---] [---+

         |

Pulse/EN |

---] [---+

 

Then we could use

Pulse/TT 

as our trigger for other operations.

Anyone ever have to do something like this before or think of a better way to approach this?

What you have seems like it should work.

As far as a better way to approach this? Easy... Don't use an alternating pushbutton when you need a momentary one...

beerchug

-Eric

Using toggle as momentary

Yes, your program works. I tested it on LogixPro simulator.
This works too and it is one rung shorter.
Rick

_______PB___________Timer 1
-------| |-----------(TON)

_______PB___________Timer 2
-------|/|-----------(TON)

_____T1 TT_________Pulse Out
------| |-----+-------( )
_____T2 TT__|
------| |-----+

A lot of us, myself included don't particularly care for the TOF instruction, but this might be a good place for it.

  PB              _____

--] [---[OSR]----| TOF |

                 |_____|

The DN bit of the TOF will come on every time PB transitions from off to on and remain on for the PRE value.

As far as a better way to approach this? Easy... Don't use an alternating pushbutton when you need a momentary one...

Click to expand...

Given my druthers, yes. This pb is on a new Moeller display that goes with the Easy 800 and cannot be re-defined right now. The unit we have for test right now is the demo unit from the Midwest Moeller office. Maybe the production version will have fixed this, or perhaps it's that way because the germans know what we need