How to configure an Arduino GPIO as an input

colporteur  Forgive me for being "that guy", but you mentioned relays.  You do have anti-spike diodes installed on all of the relays, don't you?

For those unfamiliar with the phrase, it has a lot of names.  These are the diodes installed typically right at the relay in reverse bias between hot and ground.  When the relay is turned off and the magnetic field collapses, the diode provides a low impedance path for the inductive kick to dissipate.  Without them, the inductive spike can cause quite a bit of trouble.

Troubleshooting Mantra #1:  Never overlook the easy.          It only takes one relay to drive you crazy.

colporteur  Forgive me for being "that guy", but you mentioned relays.  You do have anti-spike diodes installed on all of the relays, don't you?

For those unfamiliar with the phrase, it has a lot of names.  These are the diodes installed typically right at the relay in reverse bias between hot and ground.  When the relay is turned off and the magnetic field collapses, the diode provides a low impedance path for the inductive kick to dissipate.  Without them, the inductive spike can cause quite a bit of trouble.

Troubleshooting Mantra #1:  Never overlook the easy.          It only takes one relay to drive you crazy.

Your question is reasonable and the answer is yes. If the relay module, I purchased from the Asian distributor, schematic reads correct, there are back EMF diodes installed on the relay.

The 5VDC button press is detected on Arduino D8 which generates a D6 LOW, among other things to trigger the relay.

If the relay was a do it yourself attempt, I might not have thought of the back EMF diodes.

Break...Break...

I have a common 12VDC power supply feeding the Arduino nest. The switching power supply output has a 2amp capacity. Should I be putting a decoupling capacitor at the power input to each Arduino? I see people include it in their designs. It is not something I have done but in light of recent false triggers I'm reflecting on best practices.

colporteur  I could see where that might help, but an odd thing that playing with the non-contact voltage tester was that my wall wart power supplies for Arduino and Raspberry Pi were noisy enough to set off the detector.  I'm thinking the power input to these must be pretty noise tolerant.  It certainly can't hurt to try.  Maybe a crowbar circuit as well?

colporteur  wrote:

 

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Break...Break...

I have a common 12VDC power supply feeding the Arduino nest. The switching power supply output has a 2amp capacity. Should I be putting a decoupling capacitor at the power input to each Arduino? I see people include it in their designs. It is not something I have done but in light of recent false triggers I'm reflecting on best practices.

The Nano and UNO have local buffer capacity.

Nano:

UNO :

Sweet! Thanks JC. My knowledge level stops well short of this. Great share. Now why didn't I think of looking for a schematic?

In reviewing the schematic I have a question I was hoping you might be able to answer. My understanding was that D13 was connected to an internal LED. In this drawing D1 appears to be connected to an internal LED. What board does the schematic reflect?

This is a tiny part of a UNO schematic, just to show decoupling capacitors. It's the power LED.

TKS for the response. I will and did a search for schematics for Nano. After culling a considerable number I found one that gave me further insight into the current boards I am using. Much appreciate the insight.

I posted the Nano caps too. That's the first drawing in my reply, just under the word NANO