MadModder

So now I need to devise a way of testing the outputs. Presented as two cables again terminated in 37 pin D Sub connectors so compatible with the break out board. And again the PLC diagnostic allows me to see what it thinks that it's outputting (it's a Q word) :

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However the way (I think) that the PLC works is that it maintains a table of these bits that is updated by the PLC program and every cycle of the program the table is copied to the Q outputs.

This means that if the PLC program is running anything I write to the outputs will be overwritten in milliseconds and if the PLC program is NOT running I can't access the diagnostic facilities so a bit of a catch 22 situation.

I can do a somewhat less stringent test by reading a particular Q word and checking what is actually set but I'm not convinced that that's good enough?

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Off to scratch my head a bit !

Perhaps the summer heat has got to my brain but I've decided to resume testing to try and get this CNC lathe back on it's feet.

A full re-load of known good software still gives me several very odd error reports from the PLC inbuilt to the Sinumerik CNC control so I decided to step back a bit and do some basic hardware testing:

The PLC has 96 inputs (24 v Active 0 V Inactive) and 32 outputs of 0v or 24v. Up until now actually testing these is a physical pain - they are presented at the top of a rack with five cables terminated in 37 pin Sub D connectors - all tightly lashed together.

However a nifty 37 way Sub D break out board turned up on eBay with male and female connectors and a terminal strip allowing me far better access.

Owning a round column mill builds character.

A round column mill is the mother of invention.

It can be confusing these new fangled mills that don’t spin off a decorative pattern on the final pass.  Huh, and people pay a fortune for a rose engine….

Exactly!