Electronic – arduino – Electrostatic causing interrupt trigger

The critical point here is to control the ground of the phone.

When you manipulate your phone for its normal usage, one hand is touching it and sets the ground. Trying to do the same manipulation with a phone sitting on a table will be less reliable.

To have the same effect in the lab, you should have your phone laying on a conductive layer that is connected to the ground (or any other fixed potential) of your circuit. A simple way to do so is to have your phone laying on a copper foil that is used as the common ground of your circuit.

Your phone does not need to have direct ohmic link to ground, a good capacitive coupling is ok too.

Since you are trying to manage mechanical limit switches using interrupts generated from the edge of the signal be aware that you could get multiple interrupts when the switch first closes. This is caused by the bounce of the switch contacts.

Depending upon how the platform limit switches are used in your application you may want to consider a more robust solution that is commonly used in motion control systems. Each end of travel uses two sets of sensing. The first one that the platform would trigger near the end of travel would be one that does not use a mechanical switch. Instead it may be an optical interrupter or an indexing pulse of an optical encoder. Such signal is your logical end of travel and will be much more repeatable in terms of position detect. In fact with a controlled positioner this may be repeatable to the same position each time.

The second limit to be triggered would be the mechanical switches as you have now but connected is an emergency cutout. Such contacts would be wired directly to disable the drive signals to the platform positioner. Under normal operating conditions these contacts would never trigger and there would be some range of platform motion between when the logical trigger and when these emergency switches would engage.

Mechanical switches have a lot of hysteresis in them and will not give a repeatable end of travel position reading when you are using a servo or stepper to control the platform motion.

One final note on the emergency cutout switches. The limit cutout switch for the (+) direction wants to only cut out the drive control of (+) direction stepping. Likewise for the (-) direction of the platform. This is important because it still allows the control system to move the platform away from the emergency stop position to regain control of the platform in recovery positioning.