Hi there,
I have a more general “connection” question regarding S88 modules
Attached picture shows part of a Märklin S88 module, 1 input only to be honest.
Detection occurs when the wheels connects the continuous rail (upper one) with the insulated rail portion in between crosses on the lower rail, correct?

To have the electronic working properly I expect the ground line of the S88 bus to be connected with the brown wire (rails) of the track power.
But I'm not sure about that.
That’s why I place some question marks next to the dotted line of the track power unit.

Now my weird question:
Does the +5Vdc have any influence on the AC track power or decoders in locs.
I mean track power is a x kHz square wave and now, with detection, one adds a 5Vdc signal to the track

Thanks for your inputs!

S88

Edited by moderator 28 April 2024 11:23:32(UTC)  | Reason: Fix link

Hello Jean,
Thank you for your quick answer!

I hope this is a better link: S88-a

Suppose your central unit e.g. CS3, ESU, Tams, ... ... ... already has a connection between track power (brown wire = rail) and S88 GND (pin 2)
The dotted line with question mark on the drawing, then it's better to NOT connect any module to ground?


Regards
Alain

Ok, than you for your information Jean!
Now I know that the +5Vdc doesn’t interfere with the track power ac signal.
Btw, could you open the second link?

Because for the real question, you’ll need THIS Image
This is a schematic diagram of my S88 implementation
Upper left corner: general power supply
Lower left corner: Märklin Black MS2 with Gleisbox and CCScnitte for comm with PC
Centre: I use the track signal with AC opto-coupler for each sensor
Each AC opto-coupler output goes to Arduino Uno input, 16 inputs for each Uno
All Arduino Uno are chain linked as standard S88 chain using UTP cable
Arduino Nano is the “S88 Scanner mit Arduino” from “Meine Digitale Modellbahn”, many many thanks to him!

Now the question:
Instead of using track signal to power the opto-couplers, that is wire “A” connected to the red wire of the Gleisbox; can I feed it from my 11Vdc power supply, that is wire “ARD+”?
Of course I will also need to connect the power supply “GND” wire to the brown wire of the Gleisbox.
That will not harm my Gleisbox or decoders on the track or … … in any way?

I can’t explain why but I don’t feel comfortable doing this, it feels like connecting two different power supplies in parallel, but hey, I’m just a hobby electronics guy here.
Thanks for any input!

Thank you for your answer Per!
Can you please confirm that you also connected the ground of that 12V power supply to the brown wire of track power of your Command Station?

btw what Command Station do you use?
My concern is that expensive CS like Märklin CS3 or Esu ECos or Tams Red box are protected against such 12Vdc but maybe not the cheaper Märklin Black MS2 that I’m using.

That’s mainly why I started this thread.
Regards
Alain

I can confirm that I have connected the ground of the 12 Volt power supply to the brown wire from my Command Station.

I am using a Märklin CS3+ and Märklin S88 (60881) as feedback.

The reason why I am using optocouplers and a separate power supply, is because I have a home made signal controller; like an Arduino (but with a Microchip PIC16F627).

So I am using two optocouplers with the primary side in serie and one output to the S88 and the other to the PIC16F627 signal controller.

Best regards
Per