Hello,

I am totally new in cubicle design and I would need help to understand the right way to cable sensors to a digital signal module of family S7-1500.

I see two possibilities:

With terminal modules

The front connector and the terminal module are linked through a multiwired cable. L+ and M are also connected to the front connector and power is supplied to the terminal module through the same multiwired cable. In this way, each sensor can be connected to the channel and to the 24V.

Without terminal modules

As before one wire of the sensor need to be connected to the channel and the other to the 24V. In this case the I would supply 24V to a terminal block where I would connect one wire of the sensor and connect only one wire to the signal module.

I wonder if the SM has to be connected as well to the 24V. I believe its electronics is powered through the backplane.

Thank you for the help.

Thank you for replying.

So, what does the backplane supply and what does the L+/M in the front connector supply?

I thought the L+/M in the front connector could be used to supply the sensors circuits.

Hi,

The backplane provides communication with the cpu.

L+/M powers device and sets the potential group.

(I usually use 3level terminal blocks for sensors and such.)

on a side note, the et200sp io have different base units, one for a new potentialgroup(light) and one for using the potential group from the left module (dark)

Frank

Still not sure about it.

In a configuration when the CPU is powered from the front side and not from a PS, the CPU itself provides power to the signal modules (up to 10/12W according to the CPU). This let me think that the backplane is not only used for the communication but also for powering the SM/CP electronics. Or is it powered bridging the power from one front connector to the other?

So in the 3 level terminal block, you provide 24V to the sensors and the same 24V goes to the front connector of the SM?

i might be wrong about power to the device, but you would need to supply the potential group separately to L+/M, at least to the 1st module, maybe some modules have dip switches for potential group forwarding, otherwise you bridge them, beware of current when bridging modules.

Read the hardware manuals, all you need  will be there.

i use only 24VDC controllers.

i have a main terminal block for 24v for sensors and io supply, i run from that to L+/M and also to level1-2 on my sensor terminals, using 3rd level for input channel. That gives for a nice layout for when technicians need to replace sensors etc.

Frank

So, after a period of studying, I am still here. Reading the Siemens manual of the signal modules and some other sources, I came with the "architecture" shown in the picture.

I would say that the DI signal module requires a direct connection with M for taking the reference, it does not need the L+ that is instead provided to the sensors by means of the feed-through terminal blocks.

What do you think?

Then, please, explain to me what the 1L+ and 2L+ are used for by the signal module.

I would like to understand not just to knwo how to do it. Since, I do not have any PLC for testing, I find it hard to fully understand.