Michael Aksen
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2. Control Unit Integration


To minimize downtime, all control inputs and outputs were connected to a centralized industrial controller using an iterative and easily reversible approach. All changes were documented for easy debugging, ensuring a robust and reversible control unit integration. This iterative approach consists of the following steps:

  1. Identify a set of inputs and outputs that can be disconnected from the relay modules and reconnected to the PLC without compromising the entire machine’s functionality.
  2. Purchase all components needed for the task, such as additional input/output modules, to avoid delays.
  3. Plan out the rewiring to ensure it was as initially planned.
  4. Turn off the machine. Disconnect the wires needed for the connection. Connect the identified set of inputs & outputs to the PLC.
  5. Document the connections made between the machine's inputs/outputs and the corresponding I/O ports on the PLC.
  6. Connect the computer to the PLC and test individual PLC I/O port connections to the machine.
  7. Program ladder logic into the PLC for machine control, emulating the hardware logic that passed through the relays.
  8. Remove parallel, vestigial connections from the machine, leaving only the logic passing through the PLC.
  9. Test the system with connections solely passing through the PLC.

The iterative approach led to self-contained steps of varying size and complexity. Effective communication with the machine's operators ensured that downtime did not interfere with important tasks. I followed these steps to rewire the entire machine until all of the machine’s logic ran through the PLC. Standard AC digital input and output modules were used for most of the signals while a relay output module was used to control the state of the machine’s hydraulic and band motors. In addition, an analog module was used to collect band speed data. Following the completion of this process, I secured the PLC in a NEMA-certified electronics box that I attached to the machine to isolate the PLC electromagnetically from its industrial environment and to prevent debris from contaminating the PLC. Afterwards, two relay contact protection circuits were added to extend the life of the PLC relay module. I also installed a Wi-Fi module so that the PLC and the machine could be monitored remotely.

Me
Relay Logic vs. PLC Ladder Logic