Using PWM to address a relay just does not make any sense at all. It is something that can't be done, like addressing a letter by using a pie.Just like the word chaining and parallel mean opposite things.So your words at the moment do not make any sense, so if you want help you will have to say what you want in a better way.
could i use a shift register at each relay for the same effect?
to receive the pwm signal from the master arduino
i want to control as many as 512 relays in this way, all from the same bus.
PWM is not a communication systemYou can do that if you construct it correctly. How far apart are these relays going to be?
i was going to create my own data bus system using pwm. the first 10 bits of data would have been addressing and the next 6 bits would have been the data passed to said address. maybe I'm not explaining my system to you in a way you are used to.
What you describe is not in any way PWM. It sounds like a synchronous data protocol.
For 512 relays you will 'only' need 64 shift registers.
Scaling up brings a few difficulties like only being able to connect one output to 20 inputs, but the correct of buffers ( 74LS04 ) and good supply decoupling will see it work.However, that sort of distance is going to be a trouble to you, you will have to design the buffering correctly, it is not something that you just throw together.
I plan to have each relay on a PCB with it's own regulated 6v power supply in addition to it's dedicated 74HC595 ... I wouldn't imagine the long distances I plan to run wires would work over such distances.
speaking of distances:My current question is will the clock and latch signals from the Arduino be able to travel such massive distances? Correct me if I'm wrong but I would need to amplify this signal, right?