v5.22 is now available for testing. this is a bug fix only release 12-4-24

[cncsnw]

hello! ah yes the old NO NC nugget. trying to get away from that as it means different things to different people.
is a switch normal when some action is being made or when it is in its resting state? etc.

Some of those people are just plain wrong, and need to be educated.

There is legitimate question about whether a switch that is installed on the machine so that it is activated/triggered during normal operation should be described based on its "native" state (when it came out of the box from the manufacturer); or based on its installed state (which is what matters to the CNC and the PLC).

However, there is also room for education here.

Users who want to say a pushbutton is "normally open when it is not pressed, and normally closed when pressed", need to learn what these terms mean and how they are used.

In a given installation, there is only one "normal" condition. If we are talking about a pushbutton, then the normal condition is when your finger is not on the button.

Centroid could state in the manual that "normal" is when the machine is powered on, connected to shop air, ready to run with no fault or error conditions, but not actually running. Then everyone would know that the normal state means:
- Buttons are not pressed
- Limit switches are not tripped
- Emergency stop is released
- Air pressure monitoring switches have pressure applied to them
- Drawbar clamped / unclamped switches show the tool is clamped
- The way lube level-okay float switch is up to show adequate lube
- A way lube pressure switch would indicate no pressure in the lines
- etc..

Unless there have been some fixes in the past year, the Acorn Wizard is, in some cases, just plain wrong.
That is because in the Wizard, even though they say "green means N.C. and red means N.O.", in reality green means that the input will not be inverted (so the device is expected to have the typical state for which the PLC logic was written), and red means that the input will be inverted (so the device is expected to have the opposite states from what the PLC logic was written for.

In the case of switches that are usually N.C., such as the emergency stop button and limit switches, that happens to be correct.
In the case of switches or buttons that are usually N.O., such as CycleStart2, the Wizard is wrong.

That was the case last time I looked at the Acorn Wizard, but that was over a year ago.

Has anything changed?

Or is it still the case that if you define an input as CycleStart2, then -- because you sensibly installed a normally-open pushbutton -- specify that it is N.O. (red), the Wizard will invert the input, and Cycle Start will not work because the PLC thinks the button is continuously held down?

[cnckeith]

hello! ah yes the old NO NC nugget. trying to get away from that as it means different things to different people.
is a switch normal when some action is being made or when it is in its resting state? etc.

Some of those people are just plain wrong, and need to be educated.

yeah that was my exact stance for the last 35 years, now i am tired of trying to convince the world of what they believe to be right is actually wrong. "i reject your reality and insert my own" the software should be doing the educating.

[cnckeith]

and yes the Wizard has been "fixed" in this regard. there are no NC NO designations on it.

[cnckeith]

Or is it still the case that if you define an input as CycleStart2, then -- because you sensibly installed a normally-open pushbutton -- specify that it is N.O. (red), the Wizard will invert the input, and Cycle Start will not work because the PLC thinks the button is continuously held down?

key word here... "sensibly"

[suntravel]

Or is it still the case that if you define an input as CycleStart2, then -- because you sensibly installed a normally-open pushbutton -- specify that it is N.O. (red), the Wizard will invert the input, and Cycle Start will not work because the PLC thinks the button is continuously held down?

key word here... "sensibly"

At least there is a 50% chance to set it up right on the first try

Uwe

[Gary Campbell]

Marc makes some good points....

Unless there have been some fixes in the past year, the Acorn Wizard is, in some cases, just plain wrong.
That is because in the Wizard, even though they say "green means N.C. and red means N.O.", in reality green means that the input will not be inverted (so the device is expected to have the typical state for which the PLC logic was written), and red means that the input will be inverted (so the device is expected to have the opposite states from what the PLC logic was written for.

In the case of switches that are usually N.C., such as the emergency stop button and limit switches, that happens to be correct.
In the case of switches or buttons that are usually N.O., such as CycleStart2, the Wizard is wrong.

Having just setup an ATC system using and ETH1616 to monitor numerous functions, I can say that there are some glaring inconsistencies with how the Wizard deals with signals depending on the application, which, like Marc, I feel is wrong. There is no reason that my estop which is (preferably) is a NC circuit works just fine when set as NC (green) in the wizard works one way and my spindle temp and air pressure (also NC circuits) need to be inverted.

We are talking about the simplest of actions. 2 choices, binary. Digital zero or one to a controller.
Based on history and common usage, 1 is closed circuit, 0 is open. The controller should not care, but it does.
Centroid's onboard LEDs show this graphically, green is 1, red is 0. This should be consistent throughout the software, especially in the IO diagnostics

There are 2 states of binary circuits, "normal" (good, OK) or "triggered" (not good, not OK). This state of normal does not reflect the actual type (NO/NC) of the switch, it refers to the type of circuit, open or closed. Still 0 or 1. It must refer to the circuit as there are 4 combinations that can be used: (simple pushbutton switch as an example). Zero = NO switch at rest or NC switch depressed. One = NO switch depressed or NC switch at rest.
What is "normal" should be set by the system builder based on the hardware and application, nothing else.

If I have a switch or sensor that is either NO or NC, and set it's logic in the wizard, the systems reaction should be the same no matter what it's purpose. Previous controls I have used have simply used a zero or one to signify the "normal" state of the circuit. If set to 1 (NC) then zero (open) triggers a response from the control and if set to zero (NO) then one (closed) triggers the response.

This is obviously not the case as there is a bias that is intended to tilt "normal" to one choice (NO/NC) as preferred. The electronics do not and should not care, only the programmers do. Normally open or closed refers to the circuit, i.e., normal, OK, good, untriggered. The opposite of that setting refers to not normal, not good, triggered, i.e., alarm or message, as per the system settings.

As system builders that are safety conscious, we should strive to have as many (self monitoring) NC alarm circuits as possible, but inside the controller it should not matter. The controller should simply provide an action when the opposite state from normal is present.

It's simple: zero or one. Depending on the logic setting one or the other provides a programmed response from the controller.

"There are only 10 kinds of people in the world. Those that can understand binary logic, and those who can't" ~Me

[suntravel]

Sure the Wizard is inverting the corresponding PLC functions.

To solve this a table for each function how the PLC handle this would work.

But I bet this will make even more confusion for most users.

Uwe

[Ken Rychlik]

Actually normally grounded or not grounded might make more sense. Grounded goes green and not is red on the board no matter what the software is doing.

[cnckeith]

the software should handle all of this by simply asking the user is this the way you want it or do you want me to flip it around for you. No table, no labels needed, hook it up and go.

[cncsnw]

Actually normally grounded or not grounded might make more sense. Grounded goes green and not is red on the board no matter what the software is doing.

Unfortunately, no. For all Centroid PLC devices except the Acorn itself, input banks may be sinking or sourcing, so a closed input is not necessarily "grounded".

Therefore, the device (switch, button, sensor, or whatever) might be closing the input to 0V ("ground"), or to a positive voltage (usually +24V, but not always).

I like Keith's suggestion, but to do well it is going to take a lot of words, and ideally a couple pictures, for every input selection in the Wizard.

Code: Select all

"ToolIsUnclamped"
Closed if drawbar is fully open and tool is released.
(Include green dot, graphic of a normally-open limit switch in closed condition.)
Open if drawbar is not fully open and tool is still clamped.
(Include red dot, graphic of a normally-open limit switch in open condition.)

toggles to:

Code: Select all

"ToolIsUnclamped" with inverted input
Open if drawbar is fully open and tool is released.
(Include green dot with overscore, graphic of a normally-closed limit switch in open condition.)
Closed if drawbar is not fully open and tool is still clamped.
(Include red dot with overscore, graphic of a normally-closed limit switch in closed condition.)