In the old days, We used to have electronic controllers or PLCs to send the warnings or alarms on the panel by turning combination of light indicators on or off. To understand these signals we have to refer their operation manuals to interpret these messages. For example if they have three indicators on the panel which has Light A(LA), Light B(LB) and Light C(LC), it will be 2^3 =8 combinations of warning/alarms. To make it easy to understand , they provide us a troubleshooting table to tell operators or technicians to trace the problem. Continue reading Convert legacy control panel into LCD alarm and warning system with Arduino.