Plc

SeanLee · Jun 27, 2004

What does edge triggered mean?

Eric Nelson · Jun 27, 2004

"Edge-triggered" simply means looking for the transition from OFF to ON (leading edge), or ON to OFF (trailing edge).

Let's see if I can 'draw' it...



         LEADING             TRAILING

          EDGE                 EDGE

            |                    |

            V                    V



ON          +--------------------+

            |                    |

            |                    |

OFF --------+                    +-------------

beerchug

-Eric

Rube · Jun 27, 2004

Well drawn, Eric, but I might add something to your description for anyone who might need it. When a photoeye, prox, limit switch, etc. senses any object that moves past it, the sensor changes state at least twice, when the object first gets sensed (leading edge) and when the object is no longer being sensed (trailing edge). Applications may call for something to happen when the object first passes or when it clears the sensor.
Further, the state of the sensor could change from on to off, or off to on, depending on the sensor and how it's set up.

Eric Nelson · Jun 27, 2004

Rube said:
Further, the state of the sensor could change from on to off, or off to on, depending on the sensor and how it's set up.

Yes, that is very true. What Rube is saying is that it could also work like this:



         LEADING             TRAILING

          EDGE                 EDGE

            |                    |

            V                    V



ON  --------+                    +-------------

            |                    |

            |                    |

OFF         +--------------------+

beerchug

-Eric

Colossalnut · Jun 29, 2004

Thought it had something to do with postal service employees...

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