Should I be Worried about Random Noise Triggering Outputs

Projects General Guidance
1

I'm going to be controlling some HO Scale Traffic Lights anywhere from 2 to 8 feet away from the Arduino board. The lights run on 5 VDC and I'm programming the Output Pins to go to Ground to turn them on. Probably about 5ma or less for each LED. I plan to run CAT 5 wire from terminal strips that are wired to the Arduino. Should I be concerned about the Trains running around the track and generating "noise"? It's been suggested to me that I add a small transistor (2N2222 or equiv.) to each output line at the Arduino and then run the wires from that. Help and suggestions are appreciated. I'm still a newbie at this. Thanks!

2

An Arduino output pin is not sensitive for noise.
But I think many of us like to isolate the bad world outside from a direct path to the microcontroller on the Arduino board.
However, a few leds should be no problem at all.
Are you using one led per output pin ? I you want to use 5 or more per pin, you better use a transistor.

3

The wire pairs inside a CAT 5 cable are twisted pair, so you should perhaps be sure that each LED you feed uses a separate twisted pair to deliver the 5v. and ground. That would guarantee you pretty good noise immunity.

Good Luck

John Doner

4

For all unused pins, make them inputs with the internal pullup resistors enabled, e.g.

pinMode(5, INPUT_PULLUP);
pinMode(6, INPUT_PULLUP);
pinMode(7, INPUT_PULLUP);
5

If you are concerned with noise from trains etc running around the cable, get a shielded cable and connect the shield to ground.