Rockwell's Micro800 line of programmable controllers include support for some instructions you won't find in RSLogix.
In today's article we'll discuss one of those instructions, the Reverse Coil.
For those of us who've been using Allen-Bradley PLCs for some time now, much of how we write code is dictated by a long established set of instructions found in most A-B programmable controllers that program with RSLogix.
One such instruction is the OTE, or Output Energize, which simply turns on an output (or sets an internal bit to “1”) when its rung is true, and does the opposite when its rung is false.
But if you've ever been in a situation where you needed to turn off an output when a rung turns true, it typical requires a couple of extra instructions.
One example to accomplish that (without just negating all the input conditions) would be to replace the OTE output address with an internal bit address, and then use that bit address in an XIO (Examine if Off) on another rung to trigger an OTE with your output address.
Enter in the Micro800 and its Reverse Coil instruction.
In the Micro800, the Coil instruction is the equivalent of RSLogix's OTE instruction.
And as the name implies, the Micro800's Reverse Coil instruction does completely the opposite of the Coil and OTE instructions by turning off an output when its rung is true, and turning on an output when its rung is false.
To quote the Reverse Coil help documentation from CCW, “A reverse coil element supports a Boolean output according to the Boolean negation of a connection line state.”
Ok, that really wasn't very helpful CCW…
Now while the addition of the Reverse Coil might not seem like a big deal, once you start using it in your programs you'll likely find that it turns out to be a welcomed time saver.
And to me, it also seems to make my code simpler and easier to read.
So do you want to see it in action? If you do, check out my below video for a demonstration of how it works.
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