Debounce or Induct?

How about we start by giving bounce and debounce a definition.  Bounce (also called chatter) is generally defined as the tendency of any two metal contacts in an electronic device to generate multiple signals as the contacts close or open. Bounce could also be described as a rapid pulsed electric current instead of a clean transition from 0 to full current. Debounce is any kind of software or hardware device that ensures that only a single signal will be acted upon for a single change of state.

EasyRoll gives you one debounce timer for all 8 of the inputs available on ConveyLinx. This one timer can be found in the advanced dialogue screen under the look ahead & timing tab. ConveyLinx Debounce timer can also be thought of as an "Inhibit" time when the logic will not allow a signal change.  So once the input goes high the logical event goes high, but will not allow the signal to go low until the input is low and the "Inhibit" or debounce timer has expired.  Below is a timing chart that shows different input signals and how the logic interprets those signals.                                         


  1. The input leading edge goes high and immediately the Logic interprets the signal as "high".

  2. After the input signal (1) goes low the logic event remains high until the debounce timer expires.  If the input signal was to go high again during the "Inhibit" or debounce timer timing the signal would be disregarded.

  3. After the logic event goes low the "Inhibit" or debounce timer begins timing.  During this time an input signal would not propagate from the Input Signal to the Logic Event.

  4. The Input Signal goes high and so does the Logic event.  The Logic Event debounce timer expires before the Input goes low, so as soon as the Input does go low so will the Logic Event.

  5. As soon as the Input signal goes low it almost immediately goes back to a high state, but because the "Inhibit" or debounce timer (6) has not expired the input signal is ignored.

  6. Once the debounce timer (6) has expired the Input Signal is still high so the Logic event goes high as well.

  7. The input goes high and immediately the Logic interprets the signal as "high".  

  8. After the logic event is high the Input Signal briefly goes low then back to high.  Since the signal did not stay low long enough for the debounce timer to expire the state change is ignored and the Logic event remains high.

So enough with the timing charts already, how do I get one zone to allow a box to move further past the zone photo-eye.  It's a popular question and the answer is in the Advanced Dialog screen under the Look Ahead & Timing tab called "Forward Induct Time".  The "Forward Induct Time" is the time interval defined by the user to allow a zone to continue running after its sensor is blocked while its downstream zone is occupied. Sounds very similar to a debounce for a photo-eye doesn't it?  Unlike the Debounce Timer, the Forward Induct timer has a user configurable time value for both the upstream and downstream zones.  This Induct time can also be used when the "Reversing ZPA" feature is used at which point you would also use the "Backward Induct Timer".  

As you can see, ConveyLinx and EasyRoll is packed full of features for all different types of applications.  We'll continue writing to you with answers to all your questions and informing you of all the latest and greatest features.  If you have questions or would like to see a specific Pat's Corner let us know at , by phone at (800-764-6356) or you can find me on Google+ to discuss.