Which is the Right Choice?

I am enclosing 2 configurations of a communication system on RS485. Can someone guide me as to which configuration is better?

Thanks Ron

i personally would have said 2, but it depends on the physical layout of the kit, how long is the network, i presume quite long as there is repeaters in there ?

The current system uses figure 1, as the Master is in the center and the slaves are on either side. the distance between each slave is 11 feet. It has now to be replaced, and we have identified the place to place the master at the beginning of the line. i.e. figure 2. Will it work?

The technology of some repeaters in wireless is "store and forward" which introduce a delay from th einput to the output.

Your current setup is such that if the repeaters introduce a delay, the delay is common for all devices, whether a device is on link A or link B

Your proposed solution has the first set of devices 1-16 seeing direct comm with the master, but the 2nd set of slavex, 17-32 seeing whatever delay the repeater might introduce.

If your protocol is time sensitive, a delay might screw things up for response from 17-32 (as in Modbus RTU)

Can you determine if the repeater ahs an effective delay?

Dan

The communucation speeds are fairly low at 19.2K. The slaves need to communicate only 1 byte of information when polled.

This could be a moot point if the repeater doesn't introduce a delay. I could well imagine a repeater design that would introduce neglibible delay.

If your initial setup is still intact, you could try the alternative with temporary wiring - From the master, bypass repeater #1, and feed repeater #2 from the last slave unit in the other link.

Dan

Is the repeater necessary?

I would've tried it without first.

It might be an isolator as much as a repeater.

Before the system was destroyed by lightning, I had tried to run the system without the repeaters. It would work for sometime and would also once in a while display communication error.