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Offline Johnvr  
#1 Posted : 17 March 2012 22:14:58(UTC)
Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Hi all,

I have been converting most of my older Marklin Locos to digital operation by installing decoders, so that I can run them using my 6021 controller.
In some of the locos, I have decided to retain the original motor parts including the magnet and the armature, and to merely insert the decoder from the 60760 set to replace the reverse coil.

This could previously be done using the simple 66031 decoder but I think these are no longer produced, and in addition the 60760 decoder has address settings which can be adjusted for maximum speed, acceleration, etc. Note also that there are kits and decoders which can be used to upgrade these older locomotives to 5-pole with permanent magnet, but there is additional cost involved in this process because you have to purchase both the decoder kit and the magnet and motor kit.

An interesting solution that I have applied is to use Diodes to rectify the current produced by the decoder in order to determine locomotive direction. Here's how it works :

Attached to the old loco motors were 2 leads (one for forwards and one for reverse) and 1 lead for ground return, and worked on AC current. The reverse spring used to select either forwards or reverse, and the direction was changed on the signal of increased voltage from the transformer.

The decoders from the 60670 set have only 2 leads designed for DC current for the motor, and using the permanent magnet.
The polarity of the DC current is reversed in order to get the loco to travel in the opposite direction.
Hence only two wires are required for connecting a 60760 decoder, and not three wires as for the older AC motors.

So I inserted 2 diodes into the circuit, facing in opposite directions, and connected to the forwards and backwards leads.
The diodes allow current to flow in only one direction, hence the current flows only one way around the coil magnet, and not both ways.

You can see in the following picture how the two diodes are connected, one to the forwards and one to the reverse wires from the motor. Look carefully to see how the two wires from the motor pass through the diodes and then converge.

UserPostedImage

The finished conversion looks like this :
Please note the lovely old large bulb of a lamp in the front, which is operated bhy the function key on the controller, and also note the reversing lever on the side of the loco - testament to a bygone era when you could manually change direction of the loco by pressing the lever.

UserPostedImage

UserPostedImage

Results of this conversion are firstly a very satisfied marklin enthusiast who has spent the better part of a day just fiddling around with wires and solders and decoders, and generally got a few fingers dirty, but has a smile on his face. And secondly, a collection of favourite older locomotives which have retained their original motor parts and which can all run along together with the newer and smarter locomotives on a digital track together. Cool

Regards,BigGrin
John

thanks 2 users liked this useful post by Johnvr
Offline H0  
#2 Posted : 17 March 2012 22:52:27(UTC)
H0


Joined: 16/02/2004(UTC)
Posts: 15,254
Location: DE-NW
Hi, John,

Interesting idea. How is she driving? I wonder if she's well-behaved since you cannot disable load regulation with the 60760 decoder.

The 66032 Delta decoder is still available, supporting F0 and F1 and 80 addresses (not really a good value for the money, sets with motor parts and decoder are cheaper).

I've seen conversions with other decoders that used "blue" and "green" for the field coil connections and "plus" for the third motor connection, eliminating the need for diodes. I don't recall where I saw this, but maybe I can find the page again. They advised to disable the load regulation of the decoder for this type of conversion.
Regards
Tom
---
"In all of the gauges, we particularly emphasize a high level of quality, the best possible fidelity to the prototype, and absolute precision. You will see that in all of our products." (from Märklin New Items Brochure 2015, page 1) ROFLBTCUTS
UserPostedImage
Offline mmervine  
#3 Posted : 17 March 2012 23:12:26(UTC)
mmervine

United States   
Joined: 30/01/2006(UTC)
Posts: 1,883
Location: Keene, NH
Hmmm....where I have I seen that decoder before?
Märklin C-track, Marklin Digital & ECoS, multi-era French & Swiss
http://www.ete-ene.org/m...mervines-layout-gallery/
Offline RayF  
#4 Posted : 17 March 2012 23:26:38(UTC)
RayF

Gibraltar   
Joined: 14/03/2005(UTC)
Posts: 15,838
Location: Gibraltar, Europe
Interesting conversion!

Thanks John. ThumpUp
Ray
Mostly Marklin.Selection of different eras and European railways
Small C track layout, control by MS2, 100+ trains but run 4-5 at a time.
Offline intruder  
#5 Posted : 21 March 2012 22:57:19(UTC)
intruder

Norway   
Joined: 16/08/2006(UTC)
Posts: 5,382
Location: Akershus, Norway
Thanks for the tip, John!
Best regards Svein, Norway
grumpy old sod
Offline Johnvr  
#6 Posted : 23 March 2012 19:47:14(UTC)
Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Originally Posted by: H0 Go to Quoted Post
Hi, John,

Interesting idea. How is she driving? I wonder if she's well-behaved since you cannot disable load regulation with the 60760 decoder.

The 66032 Delta decoder is still available, supporting F0 and F1 and 80 addresses (not really a good value for the money, sets with motor parts and decoder are cheaper).

I've seen conversions with other decoders that used "blue" and "green" for the field coil connections and "plus" for the third motor connection, eliminating the need for diodes. I don't recall where I saw this, but maybe I can find the page again. They advised to disable the load regulation of the decoder for this type of conversion.


Tom, thanks for note.
She's driving absolutely fine ! I set the maximum speed down so she can leisurely travel along the track - no rush ! I also observe that the acceleration happens in increments as the speed throttle is increased - it is not linear ! I think the 60760 must have either 14 or 27 speed settings (I read it somewhere), and not continuous increases, hence the speed increments in discrete increases.

Regarding other decoders using "blue" and "green" and "plus" - you could have used these (66032?), but I believe Marklin has ceased production of this versions of decoders, and these decoders had minimal optional settings.

One has to balance time, effort and budget in deciding how advanced you would like your conversion to be. In this case, I opted to retain original motor parts and therefore original motor performance for an inexpensive conversion, and enjoyed doing the conversion and learnt some in the process. And now I can run the loco with the other digital locos.

Regards,BigGrin
John



Offline Johnvr  
#7 Posted : 23 March 2012 19:49:00(UTC)
Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Originally Posted by: mmervine Go to Quoted Post
Hmmm....where I have I seen that decoder before?


Mark - it was you who introduced me to these conversions !
Thank you !

Regards,BigGrin
John

Offline Johnvr  
#8 Posted : 24 March 2012 10:55:51(UTC)
Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Hi all,

I decided to compose a picture of the Diode connections to illustrate the concept in simple terms.

The purpose of a Diode is allow current only one way through a wire.

The Diode is required when using a 60760 decoder because the 60760 outputs DC uni-directional current, one way for forwards motion, and the other way for reverse motion. So in this instance, it allows the DC current to flow only one way around the coil, and not both ways at the same time.

UserPostedImage

So now you can do it too !

Regards,BigGrin
John
thanks 1 user liked this useful post by Johnvr
Offline mmervine  
#9 Posted : 24 March 2012 15:10:59(UTC)
mmervine

United States   
Joined: 30/01/2006(UTC)
Posts: 1,883
Location: Keene, NH
Originally Posted by: Johnvr Go to Quoted Post
Originally Posted by: mmervine Go to Quoted Post
Hmmm....where I have I seen that decoder before?


Mark - it was you who introduced me to these conversions !
Thank you !

Regards,BigGrin
John



Last year I had sent John some old Delta decoders which he used to digitize some of his analog loks. Then, last October, I had the chance to meet John (and a few other Marklin fans) in South Africa when I was there for my daughter's wedding. She is finishing up her PhD and has traveled back and forth to SA a few times in the past year. On her last trip back, she took John a few more decoders, one of which ended up in his 3003!

Märklin C-track, Marklin Digital & ECoS, multi-era French & Swiss
http://www.ete-ene.org/m...mervines-layout-gallery/
Offline Hoover007  
#10 Posted : 21 September 2013 15:39:49(UTC)
Hoover007


Joined: 07/03/2010(UTC)
Posts: 60
Location: Phuket, Thailand
Originally Posted by: Johnvr Go to Quoted Post
Hi all,

I decided to compose a picture of the Diode connections to illustrate the concept in simple terms.

The purpose of a Diode is allow current only one way through a wire.

The Diode is required when using a 60760 decoder because the 60760 outputs DC uni-directional current, one way for forwards motion, and the other way for reverse motion. So in this instance, it allows the DC current to flow only one way around the coil, and not both ways at the same time.

UserPostedImage

So now you can do it too !

Regards,BigGrin
John


Hello John.

A real novice question, what type of diode did you use. I have a real good electronics shop here but there is a language barrier. If I ask exactly I will get it.

Thanks

Robert
Offline Johnvr  
#11 Posted : 21 September 2013 20:34:42(UTC)
Johnvr

South Africa   
Joined: 03/10/2010(UTC)
Posts: 1,269
Location: Cape Town, South Africa
Robert,

I used the N4001 Diodes.

Good luck - let me know !

Regards,BigGrin
John
thanks 1 user liked this useful post by Johnvr
Offline Hoover007  
#12 Posted : 22 September 2013 04:11:54(UTC)
Hoover007


Joined: 07/03/2010(UTC)
Posts: 60
Location: Phuket, Thailand
Originally Posted by: Johnvr Go to Quoted Post
Robert,

I used the N4001 Diodes.

Good luck - let me know
Regards,BigGrin
John


Thank you John.

If you are ever in Phuket Thailand first beer on me

Robert. ThumpUp
Offline Chook  
#13 Posted : 22 September 2013 04:49:30(UTC)
Chook

Australia   
Joined: 15/08/2012(UTC)
Posts: 234
Location: Perth, Western Australia.
Robert, John nearly got it right.
The diode is actually a IN4001.
It is rated for 1 amp at 50 volts.
I actually prefer to use the IN4007 - it is exactly the same size, a couple of cents more expensive but is rated for 1 amp at 1000 volts.
The 1000v just gives you a larger margin of safety as the back EMF of some motors can be extremely high.
Over voltage failures of diodes (and most semiconductors) usually presents as a short circuit failure across the tiny internal junctions.

Your supplier will be very familiar with these components.


Regards.......Chook.
Offline GvanWyk  
#14 Posted : 09 April 2014 20:53:19(UTC)
GvanWyk

South Africa   
Joined: 27/12/2010(UTC)
Posts: 18
Location: South Africa
Hi Guys,
does this then basically imply one can use any decoder if one use the diodes?
so one does not replace the magnet, the use of the diodes creates constant flow through the coil thus creating the "permanent" magnet field?

Regards
Gerhard
Offline Webmaster  
#15 Posted : 09 April 2014 21:58:44(UTC)
Webmaster


Joined: 25/07/2001(UTC)
Posts: 11,161
My experience is that the 2-diode rectifier method does not work with true EMF decoders, really works like sh-t without a true DC motor...

Have tried LE 930, LE 130 & 6090 with this... The 60760 is supposed to be a "budget 60901" or such and I haven't tried that...
Juhan - "Webmaster", at your service...
He who asks a question is a fool for five minutes. He who does not ask a question remains a fool forever. [Old Chinese Proverb]
Offline jvuye  
#16 Posted : 10 April 2014 09:20:07(UTC)
jvuye

Belgium   
Joined: 01/03/2008(UTC)
Posts: 2,881
Location: South Western France
Originally Posted by: GvanWyk Go to Quoted Post
Hi Guys,
does this then basically imply one can use any decoder if one use the diodes?
so one does not replace the magnet, the use of the diodes creates constant flow through the coil thus creating the "permanent" magnet field?

Regards
Gerhard


Not really...

In principle you are right: feeding the field coil separately via e.g. a bridge rectifier or diodes will indeed create a permanent magnetic field, similar to what a permanent magnet would produce.

The problem is that the field produced that way is too weak to provide for a sufficient torque *unless* it is fed with a **lot higher** current needed to create the field density required for proper back EMF regulation.

But that higher current cannot be sustained by the small gauge winding of older/so called "universal" motors, and thus it will eventually fail.

A permanent magnet creates the required field without using any power...

Even large traction motors in some recent 1:1 scale locos and traction applications (trolleybuses) use permanent magnets motors with back EMF regulation these days...

And yes, there are experiments with field coils with high hysteresis material for the pole pieces and pulsed current to create the field with only a fraction of the power required...but in our case, that would mean replacing the stator too....

So for the time being, for my locos, I stick with permanent magnet motors!

If there was a miraculous "yes, go for it" answer to your question....someone will certainly let us know!
Jacques Vuye aka Dr.Eisenbahn
Once a vandal, learned to be better and had great success!
Offline RayF  
#17 Posted : 10 April 2014 17:53:14(UTC)
RayF

Gibraltar   
Joined: 14/03/2005(UTC)
Posts: 15,838
Location: Gibraltar, Europe
Using this modification is really a 'bodge'. It will make the motor work with the decoder, but it is not very efficient.

You can probably get away with using this modification if you run the loco infrequently and not under too much load. Ultimately, as Jacques has pointed out, it is likely to fail.

Proper motor conversion kits are available for reasonable money these days. For the 3003 I would go for a Lokpilot set with the correct Hamo magnet for a SFCM motor. Total cost will be about 30 Euro or so.
Ray
Mostly Marklin.Selection of different eras and European railways
Small C track layout, control by MS2, 100+ trains but run 4-5 at a time.
thanks 1 user liked this useful post by RayF
Offline franciscohg  
#18 Posted : 10 April 2014 18:41:49(UTC)
franciscohg

Chile   
Joined: 10/07/2002(UTC)
Posts: 3,265
Location: Patagonia
I have preserved the original AC motor in some oldies for sentimental reasons.....and the smell!!!!!
The Uhl 76200 does a great job for that IMHO
UserPostedImage German trains era I-II and selected III, era depends on the mood, mostly Maerklin but i can be heretic if needed XD, heresy is no longer an issue.. LOL
thanks 2 users liked this useful post by franciscohg
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