APC Installation: Within the machine control cabinet
UPS connected to the APC
The machine control cabinet is enclosed and not externally visible
APC status LEDs are not observable from outside
A main power switch is installed on the cabinet
When the main switch is disengaged, Windows performs a shutdown.
Objective: To enable monitoring of the APC’s operating status from outside the control cabinet.
In particular, it should be possible to determine from outside the cabinet whether Windows has completed its shutdown process and the APC has shut down after the main switch has been turned off.
The current solution envisages the use of an LED for external status indication.
To control this LED, the initial plan involves utilizing a Ready Relay Interface Card, model 5AC901.IRDY-00.
According to the product documentation, this relay switches when the APC is booted up and is supplied with all voltages internally.
Question: How does this relay behave during the shutdown of a Windows system?
Has anyone already implemented a similar solution?
If so, I would be very grateful for any insights or feedback on your implementation.
I am also open to alternative suggestions and ideas.
Hey Michael!
Not an expert in this area but I read through the documentation with the help of my trusty coworker mr “AI”
This is a summary of what can be read and what conclusions can be drawn from it
The Ready Relay card 5AC901.IRDY-00 is specified as follows:
Function: “Ready relay” with 1 normally closed (NC) and 1 normally open (NO) contact, max 30 VDC / 2 A.
Behavior: “Ready relay 5AC901.IRDY-00 is switched as soon as the B&R industrial PC has started up and all internal supply voltages are applied.”
That last sentence is the key: the relay is tied to the internal supply voltages and the PC’s “ready” state, not directly to the Windows OS state.
So in practice:
During normal operation:
Internal voltages present → relay energized (you choose whether your external LED is on via NO or NC contact).
During Windows shutdown (OS still running, PC still powered):
Internal voltages are still present until the PC actually powers off. So the relay will typically remain in the “ready” state until the hardware shuts down (i.e., after Windows has completed shutdown and the PC has turned off).
After shutdown / power off:
Once the APC4100 removes its internal supply voltages (after Windows has shut down and the power-off command is executed, or power is lost), the relay de-energizes and returns to its rest state. Your LED will then change state accordingly (off if wired via NO, on if you use NC, depending on your concept).
So: the relay does not show “Windows is in the process of shutting down”; it shows “PC is fully up and powered” vs “PC is off / not ready”. For your use case—checking from outside whether shutdown is finished—that’s actually what you want: LED “ready” = PC on; LED “not ready” = PC fully off.
The 5AC901.ISIO-00 option card seems to be a good solution for my requirements.
Apparently, I overlooked this option when scrolling through the APC interface options…
For the first run, it will be sufficient to route the operating LED externally to access the APC status outside our machine cabinet.
