NOVA Systems Inc.

April 15, 2016

Modicon 984 PLC Systems

Filed under: Legacy PLCs — Tags: , , , , — novaadmin @ 9:38 pm

Nova has recently completed a service call on a PLC system which dates back to the mid 1980’s. It is truly a testament to the ruggedness of a piece of electronics to still be working after 30+ years of service on a machine tool. At Nova, we have a Modicon 984 rack and CPU set up to help troubleshoot, modify and test PLC programs and I/O cards. Also, Modicon is still available through the Schneider Electric. There are ways to upgrade to newer models, an economic alternative to throwing everything out and replacing with Brand-X.

If you are having problems with a 984 system, please contact us at 414-771-7800 or

January 20, 2016

Early Programable Logic Controllers

Filed under: Legacy PLCs — Tags: , , , — novaadmin @ 8:30 pm

IMG_20160119_142730While returning from Cleveland where I had a Modicon 984 service call, I was contemplating a comparison between the 1990’s equipment and the 2016 equipment. Physical size bordered on gargantuan compared to the micro controllers of today. Approximately 400 I/O would take up the space of a 2 foot wide by 5 foot high bay. The system used coax to connect the I/O processor with the Remote I/O processor.

It is interesting how the software, with segments and networks, is remarkably similar to the modern IEC 61131 code in terms of what are now called Program Organization Units (POU). What is most remarkable is that this stuff is still running with the help of EBay and automation collectors.

Having trouble with an old PLC?  Most likely, Nova can help.  For details contact Kenn Anderson at 414-771-4800 ext 1116 or email


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