so I plan to build a house (at some point in future) and I'd like to implement some sort of home automation. Now one of the things I'd like to have is PWMed lighting. Most of the lights would be 12V LED lights which consume around 0.3A each.
I plan to have Arduino (under plasterboard ceiling accessible via a revision door) in each room which would (among other things) control the lights via TLC5940 + TLP250 + MOSFETs. This is just for illustration how it might look like in a room:
Each red line represents a pair of wires. I estimate that the longest wire could be 8m (26ft) and for that I need to use 20 AWG wire to be under 3% of voltage drop. Each light would be dimmable (provided by TLC5940 at PWM frequency of 1kHz) and powered from a single 12V power source (per room).
This all works fine on a breadboard with short cables and couple of lights but I am not sure how well it will behave with long wires and lots of lights (like 20). I already bought some wire so I can test a few lights on long wire. And it even might seemingly work well but I am trying to design it so I don't have to replace parts every month.
So here are things that I would like to ask:
Will PWM work reasonably well at such a long distance? Such long wires have not negligible capacitance, inductance and resistance so I know that I am not gonna get a square signal at the other end of the cable (far from it) but I am not trying to communicate with the light, just trying to light it up. Will the lack of square cause any ill-effects on the brightness or the LED itself?
Long wires are antennas. Could a lightning storm induct such a high voltage on those wires that would damage either the lights or the MOSFETs? Arduino will be opto-isolated via TLP250 so there should be no harm. Also if there will be any power lines (230V) crossing those wires e.g. for controlling electrical jalousies, will switching the jalousies cause the lights to flicker?
Do I need any protection for the lights or the MOSFETs? I mean like a flyback diode...
20 lights PWMing at 1kHz on 8m long wire...Will that generate lots of EMI that could distract other devices in home? Btw. there will also be dimmable LED strips (12V, 4-5A) but hopefully not on a very long wire. As I have mentioned I plan to use 20 AWG cable (might use smaller diameter cables for shorter distances) for the lights and there seem to be lack of (or more an absence of) a twisted and shielded 20 AWG cable. On the other hand 20 AWG speaker cable is available everywhere. How much of a difference is there going to be between a speaker cable and twisted and/or shielded cable (if I can get hold of some)?
Anything else that might cause problems of any kind you can think of?
Btw. I did not state it explicitly in the questions but I am not only looking for the answers but also for solutions. If you know how a particular issue might be fixed that is. I welcome and thank you for any comments/feedback.