I have gone through a number of different PLC setups for my little Omron CPM1A. Plywood, DIN rail in Rubbermaid containers, etc. But The PLC PCafter discovering how to convert an old PC power supply into a bench one then it was a matter of time before I sacrificed an old tower for some DIN rail and terminal blocks.


The most work was creating the IO port out of an old printer switch box. The parallel port has 25 pins which worksInternal IO Splicesoutgreat for my PLC. After cutting it out of the old switch I needed to splice all 25 wires with solder and shrink-tube. Obviously this is really light guage wire so it is only getting used for the small motors I take out of DVD players, VCRs and other odd items.

After (re)mounting the power supply in the chassis I drilled holes in the blanking plates for the DVD drives of the PC chassis for the front connectors. The connectors are from Radioshack, the line supply is soldered to the back . An on-off switch for the power supply is also from Radioshack.


Usually a resistor is required to put enough of a load on the power supply to keep it on. The lower for connectors are for the 24VDC supply that was added after the terminal blocks and PLC were mounted.

Front Power Connections

I did not take much for wiring space into account when I set up the terminal blocks and should have left a lot more space on the top row for the power blocks. I'm sure there are easier and more efficient ways but I was happy getting all the connections I needed. All of the IO has a dedicated terminals which then get wired into the IO splices for the parallel port. The AC for the PLC does not come from the PC power supply, and needs its own seperate feed. Eventually the plan was to chop up a PC power cable and run it from terminals inside the chassis but as of now there are still two seperate power cables for the PC PLC.PLC PC Chassis


The PC power supply does not provide 24VDC so the Omron power supply is mounted on the back grill of the chassis. Behind it, mounted on the back IO panel is the RS-232 programming adapter for the PC to PLC cable. Rather fitting this older tower had the RS-232 port knock-out on the back IO panel.

Back IO Connections

There is a DIN rail setup with another parallel port on a mounting plate. Longer leeds are spliced for connection to terminal blocks on a DIN rail, allowing for any IO connections.

PLC PC Chassis

Thebutton station is a monster from and old panel and well-used buttons, a pot with no handle and a couple push-button lights that you need to be quite careful before pressing. Another parallel port has longer leeds spliced for connection to terminal blocks on a DIN rail, this results in three seperate pieces of realestate when using the button panel which isn't ideal. The terminal blocks allow for all the IO hookup.

Back IO Connections