Digital Timer for the Assembly Line

This project involved several different technologies to enable the success of this. The driver for this project was the requirement of high visibility in a manufacturing plant environment.  The large digital displays were chosen for their large readable displays to be seen on the plant floor.  A countdown timer for manufacturing processes was requested. Each station on the assembly line has a specific time allotted for an assembly operation and at the end of the time slot, a notification such as a buzzer was energized.  As I investigated the large displays I found that the primary means to communicate information to the displays would be RS232 or RS485.  After studying the capabilities of the PLC I decided that an RS485 network had the greatest chance of success.  The communication link from the PLC port adapter to the large digital displays was ethernet cable connected configured as an RS485 network.  The PLC used a real-time clock to create a time system based on calendar days, days of the week, hours minutes and seconds.  The PLC program used ladder logic to address each digital display individually to update the time down count.   The Micro HMI was programmed to enable recipes for various time down sequences depending on the particular product being built on the assembly line.  The relay outputs on the PLC were used to power the timer group on at beginning of work shift and power off at the end of work shift.  The PLC outputs were also used to stop the timing sequence during breaks and lunch period.  This project performed in an excellent manner and exceeded expectations.