I'm thinking of 4 PIR sensors (at each end of the two aisles). And I was thinking of a reed switch at the top of the garage door opening, and one at the door into the house. And the most convenient location for the relays controlling the lights is still a 7th location. I could put 7 wireless nodes into the garage, but then I have to run power to all of them - if 5v we still have the same long wire issues, if 120VAC then I need 7 power supplies. And the local control now involves passing messages between nodes rather than just sensing input pins and controlling output pins on the same uC.
The cables supply power to the RF enabled nodes will have the same length (whether DC or AC power) as the cables going to a simple sensor, and follow the same routes.
So it would be possible to do that, but at considerable cost in money and time and complexity - compared to just running a three or 4 wire cable from the main node to a $2 PIR located 1o-20 feet away, if that can easily be made to work (perhaps with the addition of a couple of small, cheap passive components.
I don't know if I do need to worry about inductance, capacitance, reflections etc - that's why I'm asking. These things aren't usually specified one way or the other - you kind of need some practical experience. If those are indeed killers that cannot be fixed with a couple of passives, then I may go to the "make every sensor a full node with AC power supply and distribute AC to them instead" route. But wouldn't it be nice if I can do a $2 easy fix instead?
One data point - in the Do It Yourself Christamas lighting control community, they routinely get away with sending TTL or CMOS signals quite a ways from a control unit to an optoisolator input (which controls a Triac to form a SSR which does PWM dimming of an AC circuit). The signals are just a 120 Hz PWM signal but the edge timing is at 120Hz * 256 PWM divisions. You won't find much about driving a 50' cable from a TTL or CMOS output in the datasheets, but it works in this application! It would not work if you were sending a 1 Mbps signal tho.
So I have some hope that a PIR 20 feet down a cable may be able to pass back a quite usable logic signal, since it changes rather rarely. But I was hoping for some advice about the gotchas.
Remember the sensors I've mentioned are magnetic reed switches, LDRs, and PIR sensors - only the latter needs power per se separate from the signal.
