Machsupport Forum
Mach Discussion => Mach4 General Discussion => Topic started by: Mainer on September 23, 2024, 04:55:12 PM
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What determines the possible values that appear in the drop-down lists when setting the assignments for Input Signals and Output Signals using the Mach4 menu item Configure ==> Control... ?
For example I'm using a PMDX-416. I install Mach4, then I install PMDXSmartBOBUSB-Ver_0.53.263-setup.exe, which includes the profile PMDX Sample. I then run the Mach4 loader and select the sample profile PMDX Sample, After Mach4 loads, I go to Configure ==> Control... ==> Output Signals. On the line labeled X Home, I click in the box under Device, then click on the downarrow that appears to get a list of choices, I pick SmartBOBUSB. Then I click in the box just to the right of that in the Output Name column, click on the downarrow that appears, and get the following list of choices:
Pin 14
Pin 16
Why are there only two choices, and why those two? I've already assigned Pin 16 to Coolant On. Why doesn't, say, Pin 15 appear in the list? Is there any way I can expand the list of choices?
(You're probably going to tell me it's totally obvious, but I don't have any idea.)
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First thing to understand is that the pins on the PMDX-416 are predefined as either Input or Output type. You must assign output signals to an Output pin type.
The set of Output pins is: 1, 14, 16, 17 (general purpose), and Relay (dedicated). There is also an internal dedicated signal for PWM speed control via a PMDX-407 spindle control module that mounts on top of the PMDX-416. It is configured in the SmartBOB plugin control panel Spindle Config tab, not the Output Signals tab in Mach4.
The set of Input pins is: 11, 12, 13, 15 (general purpose isolated), A, B, C (non-isolated, typically used for encoder inputs), and dedicated isolated inputs for E-Stop and Fault.
You cannot use pin 15 as an Output because it is an Input type pin.
Once any Output pin has been assigned, it will no longer be in the drop down list because only one signal can be allowed to drive a pin due to electrical conflicts resulting from multiple sources fighting to control the pin. If you are trying to use an Output pin and it does not show up in the drop down list, go the the Configure > Control > Output Signals tab and scroll down through the chart to be sure that there is not already a signal trying to use that pin.
Input pins CAN be assigned to multiple signals because each signal can observe the same pin without causing an electrical conflict. This is useful when you want to wire multiple limit or home switches to one signal. If you do this you must not move multiple axes at the same time while homing. You can also define the same input to be observed as a Home signal and as a Limit signal for that same axis.
Also, the list of signals in Mach4 can be confusing because some signals will have both an Input and and Output style functions. For example "Motor 1 Home" is an input signal that Mach4 observes while homing that motor. Depending on your axis assignments that motor could be the X axis. There is also an Output called "X Home" which Mach4 uses to tell an external indicator the status of homing. That Output signal is not required and not often used. I suspect you are confusing the "X Home" output with the signal that you need for Mach4 to monitor your home switch.
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Thanks Steve. That helps a lot. Just one more detail; what is the difference between an isolated and a non-isolated pin, and why would I choose one over the other?
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Some interface boards offer isolated inputs to protect the board and the host computer from electrical interference, harmful voltages, and ground loops which distort signals.
Isolated inputs are less needed for small table top machines running lasers and electrically quiet spindles, but are useful for large machines where the host computer may be on a different electrical circuit than the machine, on plasma cutters, and on machines where the spindle may have brushes that arc a lot or a noisy VFD drive.
It is also useful to know that almost all step and direction commanded drivers for stepper motors or servo motors internally utilize isolation circuits, so the interface board does not usually have to worry about isolating these outputs.
When an interface board has isolated inputs, there will be two ground signals, one that shares ground with the main electronics of the interface board (non-isolated) and one that is connected only to the isolation circuitry and the machine under control (isolated).
If your interface board has isolated inputs, but you do not need the advantages of isolated inputs, you can connect the main electronics ground together with the isolated ground in order to simplify wiring.
Our PMDX-126, PMDX-416, and PMDX-424 boards provide isolated inputs.
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Very complete and clear! Thank you,