Hi,

Many modellers and enthusiasts still use the old – style Märklin turntable 7186 (aka 7026 / 410 N).

I was always bored by the control with the two knobs. If you want to turn from position 1 to 5 you must observe the turntable all the time and wait until it stops at every position just to start it again.

My aim was to build a replacement for the old two – knob device with a numeric control without any modification of the turntable itself. The control device only works with turntables in good condition. If the bridge has contact- problems these problems must be solved first.


Video:


http://youtu.be/OqSXKjg1Vvk


Layout:


Large scale version of the layout:

https://dl.dropbox.com/s/blw1h9knxbh7fg8/dreh300.jpg

All parts used can be bought from China for less than 25.00 EUR.

You need

Hardware (all ebay links just as a sample. I don’t have any preference for any of the sellers):

• ARDUINO UNO or clone. It also works with a MEGA. With smaller modification of the code it can be also build with a ARDUINO MINI PRO. www.ebay.com/itm/300948763268 (relay included in this special offer)
  
• ACS712 current sensor (5A Version)
  http://www.ebay.com/itm/181026550454
  
• 4*4 keypad
  http://www.ebay.com/itm/310511616357
  
• 2-relay board
  http://www.ebay.com/itm/181026509345
  
• wall-plug power supply for the Arduino. or an USB-Cable to supply it from a computer
  
• Case for all the stuff: I used
  http://www.banggood.com/Clear-E...921142.html?currency=EUR
  
  
• a computer to upload the sketch to the ARDUINO ( only for the programming. After programming the ARDUINO works as stand-alone device)
  
  and a turntable.
  

Software:

• Arduino IDE
  
• Additional libraries:
  
• Keypad.h
  http://playground.arduino.cc/code/Keypad
  
• BlinkLed.h
  https://github.com/bborncr/BlinkLed
  
• and the ino-file in the zip-file attached.

The most import part is the current sensor: It notices when the bridge has reached a position and triggers the restart.

When the sketch is installed the first time the EEPROM could contain an invalid value for the position. After installing the sketch the keys [ * ][ 0 ][ # ] must be pressed to rewrite the start-position.
At the initial start the turntable should be in the position between 0 and 7 like on the sketch below. On pressing one of the keys [ 0 ]-[ 9 ] it rides to according position. As a first test the key [ 1 ] should be pressed. If the bridge does not travel in the right direction to reach rail 1 in the shortest way, the red and green connections on the turntable must be swapped.
If the position is equal to the key pressed the loco is turned 180°.
If something is mismatched with the position of the bridge, pressing [ * ] <number of the rail> [ # ] overwrites the position in the memory according to the position chosen. In this programming mode a LED near the USB-port flashes rapidly.
If the key [ * ] is pressed by mistake, pressing [ * ] again leaves the programming mode.

Regards

Markus

Latest version 08/2016: https://dl.dropbox.com/s...sob8t/drehscheibe430.ino

Edited by user 21 December 2016 10:25:07(UTC)  | Reason: Restored lost code

Hi excellent project, i am buy things to do it, but i can´t download the codification for the arduino, it isnt in the server, someone could help me please??, thanks!

It seems like this file has disappeared - I get a message when trying to download "Error: Resource has been moved or is unavailable. Please contact the forum admin."

Hi Markus,

Awesome project. Got all the material together, but my 7186 still needs a make-over.

Studying the code: What is button A's (ziel = 17) function? I do not really understand turn=0, turn=1, turn=2.

Many thanks for your help and sonnige Grüße aus Bayern.
Patrick

Hi Markus,
I am new here, a dutchman in his sixties, who has started again, and found an old turrntable on ebay, and managed to copy your arduino scheme to run the turntable. Thank you for your scheme!! As I am using (the IB for) digital controle, I wonder if I could "easily" incorporate the arduino keyboard in the digital system (with turnoff decoder?) and nessesarily (?) changing of the (brown) mass connection of the turntable motor.
I just want to thank you again and will start searching this forum for the answers on my questions.
Greetings,
Jan Willem

Hi Markus,
There must be a way to replace the 4x4 keyboard entries by a decodertype like k83 or a digikeys decoder? Iam no expert on this, maybe someone else on the forum?
Cheers,
Jan Willem (double first name)

Hi,

Just to describe my thoughts. This is all theoretically. It is not more than vaporware. And so far, I don't know whether I will realize it.


There is no MM-decoder with +10 functions. Using function decoders will work theoretically but will use a bunch of decoders and addresses. This will work but will be practically unusable.

I think about using an older decoder for locomotives. A MM decoder has 14 or 27 steps for the speed. These steps are realized as a pulse-wide modulation which power the motor. But these steps (the length of the pulses) could be also read by the Arduino. So, the knob on the control unit could become the control-device for the turntable.

Example: If the address of the decoder is chosen at the control-unit and the knob is turned to minimum speed for more than 3 seconds (to make the command valid), the decoder sends a pulse of X milliseconds (speed step 1) this could be interpreted as a command to turn the bridge to position A. A pulse of Y milliseconds (speed step 2) could be interpreted as a command to turn to position B. And so on. This would be at least useable also without a computer and needs only one decoder.

Foreseeable disadvantage: Due to different characteristics of different decoders this will work only with a specified decoder. Mabe only with a special decoder from one series.

Regards

Markus

Thank you Daele, Markus and Per, but I am afraid this is too much for me, at least at the moment. Iam thinking more to use simpel relais to connect the wires the same way when you push the matrix board. For the time being I only use gates 4,5 and 6 for the locdepot and opposite gate 8 to enter and leave the turntable. So 4 contacts to make, like 2 turnouts on a K83 but then with minirelais.......
Greetings,
Jan Willem

Hi,

That value is so far out of range that my only idea is, that there is something wrong with the ACS712 module itself or with the wiring. Also the power-supply for the module should be checked. Does the value change when you disconnect the module?

Regards

Markus

and do you divide the result by 50?

Guten Abend. Ich habe eine Frage bezüglich des ACS712.... Wenn ich das auf dem Bild richtig sehe, denn kommt vom Trafo das gelbe Kabel, geht an + und - vom ACS712 und zum 2-Relais-Karte auf den jeweiligen mittleren Anschluß. Ist das so korrekt? Habe mir die ganzen Teile bestellt und warte nur noch auf 2-Relais-Karte und auf ACS712...
Mit freundlichem Gruß
Torsten Janner aus Deutschland

Thanks for the translation. My Chrome Browser automatically translates English into German

Hallo Markus

Very nice work you have done. I struggle a bit to make this working with Scale Z turntable 8998 / Märklin. I modified it an it seems to work from the hardware side. I had to use a mosfet to switch the polarity.
But i am still testing how to get a two diget number via keypad in and out as "schritte". And a am no progammer :( My turntable has more then nine parking slots for the locos.

thanks a lot
Jan

Edited by user 25 June 2020 21:26:54(UTC)  | Reason: made progress

Hi All,

Here is an article by John Barry that controls the 7186 turntable with Arduino and can be interfaced with TrainController software.

7186 Turntable Conversion with Arduino Operation

Link corrected 31-12-2024

Edited by user 31 December 2024 05:19:08(UTC)  | Reason: Not specified

Hi Marcus,

I created the setup based on your description, but somehow things go wrong.
After an initial setting of the proper track, the turntable will properly move to the track indicated on the keyboard.
However, every subsequent selection will move only one track.
If I re-enter the actual track, the story repeats itself: the first move goes OK, any subsequent move in skipping 1 or more tracks will go wrong.

The one thing I notice is that after the first correct move (where every track is properly skipped), in the subsequent moves I hear the relay being pulled way before it should actually be pulled. The number of times the rely is pulled is not in line with the number of tracks that should be skipped (although it roughly matches).
Because I use a 3 column keyboard (without the ABCD column), I changed the code slightly:

const byte ROWS = 4; //four rows
const byte COLS = 3; //three columns
char keys[ROWS][COLS] = {
{'1', '2', '3'},
{'4', '5', '6'},
{'7', '8', '9'},
{'*', '0', '#'}
};

//Anschlüsse des Keyboards am Arduino. Wenn die Eingabe seltsame Ergebnisse ergibt, müssen die Keyboard Anschlüsse
//um 180° gedreht werden oder die Pins angepasst werden

//Connections of the keyboard. If you get strange results the pins of the keypad must be connected in reverse direction

//rows/columns en pin-assignment aangepast ivm 4x3 keyboard
//byte rowPins[ROWS] = {2, 3, 4, 5}; //connect to the row pinouts of the keypad
//byte colPins[COLS] = {6, 7, 8, 9}; //connect to the column pinouts of the keypad
byte rowPins[ROWS] = {3, 4, 5, 6}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {7, 8, 9}; //connect to the column pinouts of the keypad

Did I do something wrong in my change or should I change some other lines tooo?

My programming skills are a bit rusty after almost 35 years...

Joost
p.s. once the program works OK, I will add a DCC-interface to my Arduino, see ArCoMoRa

Hi Harold,

I downloaded the blinkled.h library from https://github.com/bborncr/BlinkLed, you'll find the instructions to install the library on that page.

I really doubt that the saving of the position is the culprit, it has to do with the timing/trigger of pulling the relay. I haven't figured out how that works. As I wrote before, it has been a while since I have been programming...

Joost

Hi Harold,

I did not dig as much as you into the code, but your logic does make sense. The turntable itself seems to work flawlessly, although I have to admit I did not check the actual power consumption during operation.
I checked the operation again today, just to make sure I was not sharing nonsense. When controlled by manual operation, it runs fine.
When I operate it via the Arduino, the number of times the relay is indeed pulled in line with the number of tracks it has to move, but it pulls the relay just somewhere in between tracks.
As I agree with your description how the code , I will now first clean the electrical contacts of the turntable and come back to this discussion after that.

Regards,

Joost

Hi Markus,

2 months ago I retired, so finally enough time to spend more time on our Marklin hobby.

I still encounter errors in the operation of the turntable in combination with the Arduino. I took the turntable apart and cleaned it thoroughly, but I still encounter short intermissions in the turning process, resulting in a miscalculation in the number of tracks.

The best way to avoid this, is to put a small delay in the reading of the interruption. I checked your code, and think that this part of the code is taking care of that:

void loop() {
led1.update();
float ampere = 0;
for (int i = 0; i < 20; i++) {
ampere = ampere + (abs(analogRead(A2) - 512));

delay(1);
}
pos = last;

But also in
while (schritte > 0) {
ampere = 0 ;

for (int i = 0; i < 50; i++) {
ampere = ampere + (abs(analogRead(A2) - 512));

delay(1);

}

My questions are:
- is this indeed the proper code that is measuring the interruption?
- if so, which value in which part of the code should I increase to overcome erroneous interruptions?

Looking forward to your reaction (or from somebody else )

Regards,

Joost

Hi Jan Willem,

There are basically 2 challenges:
1. to get a long enough starting pulse
2. to overcome contact problems when the bridge is moving and the software thus assumes that it has already found the next track.

In the Koploper forum Chris Burger managed to get things going in a different way, see https://www.koploperforu.../topic.asp?TOPIC_ID=6987 (all Dutch sorry for the other non-Dutch speaking readers). He also had the challenge of power interruptions during the traveling of the bridge and he added a delay.

Joost

Hi Markus! I have a question. What happend If i want to use it with a cs3 wich wire i have to change? Thanks