in my project i have 5 nodes interconnected with RS-485 channel, and all nodes have one switches when switch is pressed then controller pin goes low and master performs the operation.
it was good at testing,but at validation controller gets trigger automatically without pressing the switch.so what could i take care of ?
>all my nodes are within 20-25 cm of a 440V supply
Bikas, you mean when a switch of a node is pressed, the node's controller pin goes low and send a package to the master, right?
How you test the system?
I think 25cm is really a short distance for RS485 and should not have much problem on noise issue. In fact I have tried to use simple non-twisted non-shielded wires for RS485 for similar distance with no problem.
You should decrease Pull up(or pull down) resistor. inserting a little capacitor in parallel with switch also improves noise immunity.
Also you can sense "State" of switch instead "Transition" of switch.