Re: How many number of nodes can be connected on an RS485 Bu
Everything is a matter of total impedance on the bus.
The standard maximum load on an RS485 bus is 32UL. That means 12K/32=375 ohms minimal total impedance. This is the minimum impedance which allows a correct common mode for any of the 32 receveirs on the bus with an 120 ohm terminator. Note the current request on such bus, is I.
Increasing the number of UL is possible only if the current is decreased and the impedance of the receiver is increased. For a 96k impedance, 96/375 = 256 UL, with a current much smaller than on the 32UL bus. I1 = I/8.
The common mode voltage for 256UK and 32 UL must remain the same specified by the RS485 spec datasheet.
Now, which is the difference? The 32 UL standard is able to communicate up to 1km. The 256 UL standard will have a smaller noise imunity because the current is 8 time smaller. How long will be the cable ? I don't know, never tested 256UL.
I hope you've understood now.