S7-1500 number of inputs problem

Hello again i encountered another problem during my testing with the S7-1512C-1 plc. In a project i use a lot of diffuse sensors and i found out that after mapping 34 of the sensors, at the 35’th sensor and the ones after it are having detection problem in tia, they flicker from on to off at different intervals. Is this problem happening because the plc has 32 physical inputs? (note: I already made the settings so that the physical adresses dont overlap with the ones used in FIO).

Hi @NecroPlayer,

‘Flickering’ inputs are usually caused by the PLC overwriting the inputs sent by Factory IO.
The issue is described in this topic.

You should also check whether there are other input modules that could be using addresses starting at 32.
There is also the possibility that numeric inputs from Factory IO could be using addresses that overlap the addresses used by boolean inputs.

Is this problem happening because the plc has 32 physical inputs?

No, Factory IO should be able to send inputs to the PLC, even when there are no corresponding physical inputs.

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I seem to recall a similar issue some years ago when I inadvertently addressed what I thought was available I/O only to find they were automatically assigned to one of the modules I was using at the time (or one of pre-defined technology module channels). I had to offset my I/O by quite a bit. Can’t seem to put my hands on my notes because the 1500 was borrowed.


Yeah, TIA starts with the Byte 0 IIRC for any periphery I/O.
I set my Siemens Driver in Factory IO to Offset 1000 or something because for normal testing and simulation purposes I normally don’t use 1000 Bytes of I/O.

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