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How to configure an Arduino GPIO as an input

colporteur

What would you recommend to reduce the spurious triggers on the input of a Nano?

 

Up to now I have been using Arduino Nano microcontrollers for animation support on a model railroad without issue. With the recent completion of the airport scene, I started to experience issues of Nano's receiving spurious triggers. At first I thought maybe I set the input resistor to high, so I reduced the value from 100K to 47K. I got some relief but it has recently raised it ugly head again. Without the resistor the triggering is unpredictable.

 

Currently there are 5 animations that have button control.

  • Aircraft landing simulation (LED)
  • Hanger building Lighting (LED)
  • Simulate arc welder at bench (LED)
  • Compound gate open/close (28BYJ-48 ULN2003 controller)
  • Hanger aircraft engine startup/shutdown (L293 brushless motor)

 

The compound gate sometimes triggers the Hanger aircraft engine animation and vise versa. The input circuit I am using for the Nano is minimal.  These two animations did share the same twisted pair from the button panel. I have separated the animations button to different pairs and I have some relief. I'm thinking maybe there is a simple way to dampen inputs so they are not as sensitive?

 

I'm hoping someone might have a suggestion/best practice recommendation for connecting inputs, that is designed to eliminate the problem.

 

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  • in reply to baldengineer

    This suggestion is a first for me. I have seen typically 10K pullup or pulldown but not 4.7K or as low as 1K.

     

    I used a 7ft piece of CAT6e to wire a  button panel to a distribution frame. One conductor provides 5VDC to all the buttons with the seven remaining wires individually connected to a button. The two spurious Nano's were each sharing one conduct from the same pair. I separated them to different pairs and haven't seen the problem.

     

    The twists in the CAT6e cable pairs are pretty intense. I had worked with CAT5 but was taken aback at the construction of the CAT6e. I am using the cable as a cross connect wire which is not as it was designed for. I suspect the intense twists can't but help cross talk.

     

    I like the resistor suggestion because of the simplicity. I will move the simulations to the same pairs again and try the lower resistor value to see what affect it has.

  • in reply to colporteur

    I can't recall if Cat6e is shielded or not, but in either case, at 7 feet, it's almost guaranteed to be picking up electrical noise, unless the shield (if it exists) is connected to your signal ground. In any case, it is quick to check, just put the 'scope onto the cable at the microcontroller end and see what you capture.