hemanteda
Member level 1

RS485 burning up when connecting to thermostat/relay module
I'm trying to connect a micro-controller based RS845 node to a relay controller (PIC micro + MAX485). The relay controller is mains powered and supplies 24V AC to nodes (has internal 220 to 24V AC transformer). My node is powered from this 24V AC, I'm using a bridge rectifier +LM2596 based circuit to get 5V DC output. Here is what happens,
When I power my node from a separate transformer of the same type and rating (220VAC to 24VAC) and connect just the RS485 high & low wires to the relay controller, all works well.
If I power my node from the relay controller but leave the RS485 unconnected, output voltage is still 5VDC and nothing heating up. Then as soon as I connect the 485 connections, the PIC starts to receive a lot of null chars, everything starts to heat up, and one or the other component blows up.
I'm in desperate need of some expert advice, thanks
I'm trying to connect a micro-controller based RS845 node to a relay controller (PIC micro + MAX485). The relay controller is mains powered and supplies 24V AC to nodes (has internal 220 to 24V AC transformer). My node is powered from this 24V AC, I'm using a bridge rectifier +LM2596 based circuit to get 5V DC output. Here is what happens,
When I power my node from a separate transformer of the same type and rating (220VAC to 24VAC) and connect just the RS485 high & low wires to the relay controller, all works well.
If I power my node from the relay controller but leave the RS485 unconnected, output voltage is still 5VDC and nothing heating up. Then as soon as I connect the 485 connections, the PIC starts to receive a lot of null chars, everything starts to heat up, and one or the other component blows up.
I'm in desperate need of some expert advice, thanks