If you absolutely do not want to use the module and want the LEDs OFF, you need to look into "Options handling" as a way to configure hardware at PLC startup - or on-the-fly during runtime as needed.

Me personally, if it is not hurting anything, I keep the electrical enclosure door closed and safely ignore those LEDs hidden behind the door.

milos23

Hi,

Why are all 4 LEDs constantly ON, I don't use module in current program at all?

If that were a digital output module, then your thinking would accidentally be correct.  If nothing was wired to an unused digital input module, those LEDs would likewise be off.

However, that's about it for status LEDs being off.  If an installed and configured module's IO channel is not in an error state, it needs to be GREEN.  OFF could indicate a potential channel failure for a configured module.

Digital outputs are of course the real exception - at least non-failsafe modules.  They are only ON when the PLC turns them on, either by plc logic, force or watch table or manual intervention using TIA Portal (or even an HMI).

Hope that makes sense.  The LEDs are part of the system diagnostics.  As long as a module is configured, LEDs will display whatever they are supposed to display.

FYI, every S7-1200 module in the S7-1200 system manual includes a section about that module's LEDs.  You really should download that manual, learn to find your modules by part # quickly, and then search for LED status meanings.  It will save you much confusion in the future and really save you time since you have the answer within 15 seconds of copy/paste the part # from the portal project into your PDF reader's search box.

milos23

I was just interested do they have to be ON if none of inputs is used in program.

I tought naively that they should be ON only if input is used.