Hi, I designead a small board with the Attiny 85 witch I will put in each switch box for the lights around the house. The Attiny on the board is connected to a BC547 switch a SSR to control the light attached to it. On the shematics below you will se the switch witch is the standard wall light switch for normal use and the 30M long wire comming from the Arduino for remote control. Each pin of the Attiny is connected to a pulldown resistor. My question is how can i filter the noise comming from the 30M wire? I mean i did not tested it yet but i will assume that some noise will be picked up by the wire and trigger false readings from the Attiny. I will try to solve this problem with electronics and not to touch the code. The other schematics is the Attiny board. The capacitor is for smoothing the voltage, is 0.1uf enough?
Low voltage wires have no business in a switch box. There's too much danger of them getting energized if there is some kind of short.
Well, it should not be a problem because a short happens once in two years. I want to put some kind of protection because if it happens that the wires get energised from a short or something other it will blow up the protection. That is why i opened this post. I thinked to put a optocoupler but i want to consider other possibilites.