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How to connect a 7186 turntable to a 7687 decoder
 Joined: 10/07/2019(UTC) Posts: 25
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Hello, markliners. How would you go about connecting a 7186 turntable (not 7286!) to the 7687 decoder? The decoder box does not contain a ribbon cable. The 7186 does not have a ribbon cable. The connection diagram in the decoder and the 0308 digital book show a ribbon cable. Thanks and best regards, Tony   
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Joined: 05/06/2004(UTC) Posts: 16 Location: Atlanta, GA
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Tony,
You can't, at least not without major modifications to the turntable. The 7186 is an analog device. Therefore it has no way to provide any feedback to the 7687 decoder which is a digital device. That feedback tells the decoder the position of the rotating bridge of the turntable.
There are different ways to automate the 7186 like sensing the track current from the spoke tracks. (the spoke tracks are not powered up until the bridge is aligned with one and that can be used to determine the bridge position). But that requires building some device to do that.
-=tom=-
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Joined: 10/02/2006(UTC) Posts: 3,997
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Originally Posted by: torle  That feedback tells the decoder the position of the rotating bridge of the turntable. I am not aware of any feedback from any Turntable. The output of the 7687 to the 7286 is analog and one-way as far as I know. Do you have any evidence of digital feedback? How does the TT even know where the bridge is? There are no position sensors. |
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 1 user liked this useful post by DaleSchultz
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 Joined: 04/02/2011(UTC) Posts: 3,562 Location: Paris, France
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Hi Tony The key difference between the 7186 and 7286 TurnTables (TT) are: - 7186 has a "universal motor" (both for AC and DC) - 7286 has a DC motor Here is the 7286 wiring (note that the 3 diodes on the TT are not represented)  As you can see the contact in the TT which opens in front of each track position can be used to report the position The 7186 wiring (thanks to thetraindoctor.co.nz)  The wiring diagram is extracted from the train doctor as seen from here http://thetraindoctor.co...186_turntable_hints.htmlI don't know the 7687 decoder enough to provide further guidance. I hope this helps Cheers Jean |
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1 user liked this useful post by JohnjeanB
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 Joined: 23/07/2014(UTC) Posts: 8,472 Location: ENGLAND, Didcot
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As others have pointed out the two turntables use different motors. The 7286 uses a DC motor, so if the polarity to the motor is reversed the motor will turn the opposite direction, allowing the turntable to turn either direction.
The 7186 turntable has a "universal" motor which will run on AC or DC - but with DC unless you reverse the current through the magnet it will always turn the same direction (irrespective of the DC current direction) - which is the reason it will also run on AC.
The motor as fitted to the 7186 turntable uses standard loco motor parts, so what you COULD do is use a loco upgrade kit to change the field coil magnet to a permanent magnet, and fit a 5 pole armature. I would recommend changing to a 5 pole rotor as this may be needed to get the current low enough for the 7287 decoder to handle, the motor in the 7286 is quite small and geared well down, and I don't know what the current carrying capacity of the 7287 is.
You may then need to look at the release solenoid, to see if the driver for that has enough grunt. Again the solenoid in the 7286 is quite small. At worst it may be necessary to rewind the solenoid with more turns of finer wire to get the current low enough, but there is a trade off when you do this. It may be better to have the decoder operate a relay that then drives the solenoid.
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2 users liked this useful post by kiwiAlan
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Joined: 10/07/2019(UTC) Posts: 25
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I'm partial to a motor upgrade and also a relay to operate the solenoid. But I'm still unclear about the ribbon cable wiring to the 7687 which has six wires. This diagram:  and this: http://www.hjb-modellbahn.de/Elektrik/Elektrik.htmis taking me down the German internet rabbit hole. Edited by user 30 August 2020 19:21:12(UTC)
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 Joined: 25/09/2006(UTC) Posts: 945 Location: Sydney, NSW
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Hi Antonio,
Don't use the 7867 with the 7186 TT as you will destroy the stepper motor control in the device.
Use a m84/k84 device to replace the push button panel.
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Ross
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1 user liked this useful post by Ross
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Joined: 25/09/2006(UTC) Posts: 945 Location: Sydney, NSW
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Hi Dale, The 7687 sensors the relay switching on/off by the mechanical interlock and it counts the number of steps for programming. Originally Posted by: DaleSchultz Originally Posted by: torle That feedback tells the decoder the position of the rotating bridge of the turntable. I am not aware of any feedback from any Turntable. The output of the 7687 to the 7286 is analog and one-way as far as I know. Do you have any evidence of digital feedback? How does the TT even know where the bridge is? There are no position sensors. |
Ross
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1 user liked this useful post by Ross
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Joined: 23/07/2014(UTC) Posts: 8,472 Location: ENGLAND, Didcot
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Originally Posted by: Ross Hi Dale, The 7687 sensors the relay switching on/off by the mechanical interlock and it counts the number of steps for programming. Originally Posted by: DaleSchultz Originally Posted by: torle That feedback tells the decoder the position of the rotating bridge of the turntable. I am not aware of any feedback from any Turntable. The output of the 7687 to the 7286 is analog and one-way as far as I know. Do you have any evidence of digital feedback? How does the TT even know where the bridge is? There are no position sensors. The motor in the 7286 turntable is an ordinary DC motor not a stepper motor. The decoder just times how long it expects to take for each track increment, then releases the solenoid which cuts of the motor when the solenoid lever indexes into the drive gear on the end of the turn table bridge. The only form of feedback that the decoder can get is sensing when the current drawn by the motor is turned off when the bridge indexes at the next track.
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Joined: 10/02/2006(UTC) Posts: 3,997
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Does the 7286 have a stepper motor? Surely not.... last time I saw mine it looked like a crappy DC motor.
If there is no stepper motor how would the 7687 be able to control it with stepper motor controller?
I think a stepper motor in the TT would be a grand solution.
Interesting that it counts relay actuations, (still analog if it does) - I thought the relay was actuated by the controller, but it must be a good 15 years since I was able to view the mechanism. (I landscaped the top edge in and now I cant remove the bridge.)
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Joined: 23/07/2014(UTC) Posts: 8,472 Location: ENGLAND, Didcot
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Originally Posted by: DaleSchultz Does the 7286 have a stepper motor? Surely not.... last time I saw mine it looked like a crappy DC motor.
Definitely a DC motor. Originally Posted by: DaleSchultz
If there is no stepper motor how would the 7687 be able to control it with stepper motor controller?
If it is anything like the LDT controlller it is a dual half bridge controller, which when driven with appropriate waveforms can drive a stepper motor, but by driving the two inputs appropriately makes a good DC motor driver. Originally Posted by: DaleSchultz
I think a stepper motor in the TT would be a grand solution.
Interesting that it counts relay actuations, (still analog if it does) - I thought the relay was actuated by the controller, but it must be a good 15 years since I was able to view the mechanism. (I landscaped the top edge in and now I cant remove the bridge.)
I don't believe it does, I suspect it is like the LDT one and does it purely on time since it was actuated. The LDT one has a potentiometer to set the speed to allow for variations in motors (it will also handle the SB motor).
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Joined: 05/06/2004(UTC) Posts: 16 Location: Atlanta, GA
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Dale,
I didn't mean to imply that the bridge sends digital data to the decoder. It just sends some sort of signal or pulse every time the bridge passes a spoke track and makes that loud clacking sound. (Maybe you could call that digital data) It's then up to the decoder to figure out the actual position of the bridge from counting these pulses, the starting location of the bridge, and the direction of rotation. The decoder, during its initial manual setup, also maps the active track positions and uses that info to direct the bridge to only stop at active locations.
At least that is how it was explained to me by someone from Märklin way back when Märklin first offered it.
-=tom=-
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Joined: 25/09/2006(UTC) Posts: 945 Location: Sydney, NSW
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Hi Alan/All,
The motor is DC and my reference to a stepper motor control is not the type of motor but a simple term to explain how it counts the number of steps to locate the correct position.
Tom (torle) explained it well.
The bottom line is if the the 7687 decoder is wired to the 7186 turntable there is a great chance that the decoder will be destroyed.
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Ross
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Joined: 10/02/2006(UTC) Posts: 3,997
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indeed, I did install a 7687 at one stage and did all the programming. It would work and then a few months later will have lost all the programming again. It was such a PITA I gave up on it and and now just switch the motor on and off and reverse polarity as needed with a K84. I still use time delays to know how far it has moved. My plan is to one day use positive feedback using sensors. Using the center contact as a position sensor has the problem that the little tongues have to be available, and those short against the rails. In order to prevent the shorting, I have disabled the contacts: https://cabin-layout.mixmox.com/2004/12/Digitizing-turntable-7286.htmlIf the relay engages every revolution of the gear that runs against the outer wall, then that would certainly enable a counting of the spokes, and it may be easy to couple that to one of the rail wires to go into an s88. Nice. |
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1 user liked this useful post by DaleSchultz
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Joined: 04/02/2021(UTC) Posts: 480 Location: USA
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Originally Posted by: HerrDoktorBD Hello, markliners.
How would you go about connecting a 7186 turntable (not 7286!) to the 7687 decoder?
The decoder box does not contain a ribbon cable. The 7186 does not have a ribbon cable. The connection diagram in the decoder and the 0308 digital book show a ribbon cable.
Thanks and best regards,
Tony
I like to convert old analog stock to digital operation. Posts about the 7186 turntable were not working for me, but here is my solution. The primary issue is digital power vs old AC power to turntable, while also controlling the k84 decoder. The turntable will not function with digital power, so the yellow lead must come from an accessory transformer that shares ground with track (or turntable ground). The k84 is needed for left/right turn (#4) and the long pulse (#3) to get going; k83 for solenoids won't allow control. Importantly, once the k84 unit gives a start pulse it needs to be turned off. The turntable will continue to rotate (with less noise) and stop at next closest track (just like old manual switch does). The k84 start and stop is easy to program in cs3, but is manual for older intellibox. Maybe there is a more clever solution to stop pulse in older digital drivers. Pic of k84 connections is below. Yellow and white go to accessory transformer; red and brown to digital power. This works for me.  |
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 You have been a member since:: 27/02/2008(UTC) Posts: 297 Location: Santiago
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Originally Posted by: DaleSchultz indeed, I did install a 7687 at one stage and did all the programming. It would work and then a few months later will have lost all the programming again. It was such a PITA I gave up on it and and now just switch the motor on and off and reverse polarity as needed with a K84. I still use time delays to know how far it has moved. My plan is to one day use positive feedback using sensors. Using the center contact as a position sensor has the problem that the little tongues have to be available, and those short against the rails. In order to prevent the shorting, I have disabled the contacts: https://cabin-layout.mixmox.com/2004/12/Digitizing-turntable-7286.htmlIf the relay engages every revolution of the gear that runs against the outer wall, then that would certainly enable a counting of the spokes, and it may be easy to couple that to one of the rail wires to go into an s88. Nice. That is rare, I have the 7687 and I have never needed to re-program after some time. I did the programing with my CS2 and it has been working since then for almost 7 years. Actually I have upgrade to CS3 and it works just fine. It has not lost the memory. Probably you have a faulty 7687. Regards Eduardo
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Joined: 07/01/2015(UTC) Posts: 729 Location: England, Suffolk
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Since the request was for a 7186 I would stick to the original product!!!
This is what I found in the Marklin Digital booklet.
You need an M84 or the components shown in the picture.
I recall Marklin telling me that the m84 is better to manage the 7186, compared to the m83
2 x 7245 universal relays
1 x K83
1 x S88 if you want to program the tracks (to me useless)
I have managed to get the crane to work in this same configuration, more or less.
HTH
Marco
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Joined: 07/01/2015(UTC) Posts: 729 Location: England, Suffolk
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Sorry, forgot attachment :-(  Here it is
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How to connect a 7186 turntable to a 7687 decoder
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