This is what I’m doing. I’m sending a frequency on a pair of CAT5 wire (High speed switching 12V, @ 1 KHz). Slaves are connected to this pair at different places & they will read this frequency.
Those are my questions
Can these slaves get the same frequency as send by the master?
What problems will occur in real life?
Do I need a pull down resister on the master transistor?
What about adding 500 pieces of slaves, in other words paralling 500 opto couplers to the same bus?
Way too vague... as posted, 500 parallel 4.7k to opto LED drives would be one Hell of a high current load. There are ways to deal with very wide fanouts, this isn't one. Each slave has to be high impedance to the bus, so galvanic isolated or equivalent.
Quality help is proportional to the problems' descriptive accuracy... <<<)))
I think you're missing my point: direct driving a bus with that many loads just isn't done. Each slave has to power its' own tap on the bus, the bus will have enough problems with noise issues.
If opto isolation isn't required, look at RS422 or 485 data bus options.
Again... Vague, the "frequency" of 1k isn't described as digital, analog or data embedded.
If you drove 500 of the opto couplers in parallel, that would be about 1A of current from your transistor if you drove the transistor base to 12V. I see no particular problem with doing that. The low impedance of the load will minimize noise problems. You don't need any additional power or isolation.
All the slaves will receive the same frequency.
I wouldn't expect any problems running this at a 1kHz square-wave.
You shouldn't need a pull-down resistor on the transistor.
Brilliant Carl.Your post saves my time to think of a new way of doing.
The number 500 I just pull out from the air actually it will be below 100 slaves.It is better to shift to PC817 because it will operate from 5mA current.
Creating your very own protocol from the ground up huh?
Communicating with #100 will be an altogether different experience
than communicating with #1. Read up on existing serial protocols
before reinventing the wheel. You should be able to address 255 nodes with
an 8 bit address right?