GrandAlf
Advanced Member level 2
We have an installation with around 70 units with a PIC16f648 driving a low power rs584 chip. These run via a a central 12v psu. Each unit has onboard 5v reg, filtering and surge suppression and is wired in various star and series configuration. These transmit back to a single receiver in an indicator panel. Voltage is down to about 7v at the furthest point. The problem we are having is that we are getting is that the pic chips are failing, measuring around 15ohms across the power pins when failed. There has never been a failue of any other component on the board. Other than RS485, all inputs are opto isolated. We have many almost identical systems, with no issues at all. Only thing I can think of is the difference in voltage is causing a problem. PSU and various other things have been changed to no effect. This is really getting difficult and I am at a complete loss. Any advice would be really very much appeciated while I still have some hair left. Have thought of opto isolation in sections, or extra power cables, but not sure if it will help. Thank you