ZIMO ABC Braking Unit

[Shropshire Lad]

Afternoon all!

I need to make an ABC board to stop my locos diving off a lifting bridge. They mainly have MX69x decoders fitted and can pull up to 2.5 Amps each. As I occasionally double head them I need a 5 Amp unit. The manual says 3 diodes and a Schotky diode is required the question being which diodes would do the job? 

Thanks Colin

Edited March 29, 2016 by Shropshire Lad

[RAF96]

Try this  - my equivalent to a Lenz ADCC BM1 module, which works fine and you may use freely  - no royalty or other such fee.

 

http://www.rmweb.co.uk/community/index.php?/gallery/image/24940-assymetric-dcc-generator/

 

Read about ADCC and the various modules on Lenz web site.

 

BM2 and BM3 module equivalents are in work elsewhere on the inter-web using PIC technology.

 

The BM1 module works when a loco hits an isolated section where there is a break in the RH rail in the direction of travel.

 

Locos can be set to slow or stop and/or ignore if travelling through the section in the reverse direction, so you could make a DCC shuttle arrangement given a bit of thought.

 

Be aware suitable Lenz decoders work on distance after detection but Hornby Sapphire decoders work on time after detection so control is to say a tad variable.

 

Please repost with your ADCC experiences.

[Nigelcliffe]

The circuit with "3 diodes and a schottky" is a bit more efficient in having a lower voltage drop than the 5 diodes above.   The 1N4001S might be a under-powered for large scale locos pulling 2.5A.

The "3 diodes" just need to be fast recovery rectifier diodes, 1N5001 or similar is fine.   The Schottky just needs to have enough current capacity.   The Schottky goes in the diode string directly between the track feeds, the 3 diodes form the alternative longer route string. 

 

(Read the post carefully, it does make sense !)

 

- Nigel

[Shropshire Lad]

Thanks for the link. It isn't much use to me unfortunately as Zimo decoders require less of a voltage drop and as it's a copy of the Lenz unit it won't cope with the higher current my trains pull.

Nigel that's spot on sir, I'll order some components and get soldering!

[Suzie]

UF5400 is a the high power diode I use for this, they are 3A high speed diodes so will make a 6A BM1 equivalent. I have picked these up quite cheaply but it might be worth trying to find some low cost equivalents (any of UF5400-UF5404 will do). I find it is usually cheaper to get all the diodes the same rather than two different types. I think that Rapid is the cheapest source I can find for them at the moment:-

 

http://www.rapidonline.com/axial-rectifier-diodes/3a-ultrafast-rectifier-diodes-29686

 

 

I use the 4+1 arrangement all with the same diode to give a minimum 1.5V of asymmetry, 3+1 only gives 1V which might be pushing it a bit, but I think that the Zimo decoders can be adjusted to make them more or less sensitive. These diodes do tend to exhibit lower forward voltage than the 1V specified in the data sheet when lightly loaded (i.e. a slowing and stopping train!) so assuming 0.5V forward voltage drop per diode is not unreasonable. It is the minimum asymmetry you have to worry about - too much will not hurt.

 

There are a lot of different types of Schottky diode, where there tends to be a trade-off between low forward voltage and other characteristics (like high current) - so not all Schottky diodes have a very low forward voltage so you may be just as well to use a fast recovery diode like the UF54xx instead anyway.

Edited March 29, 2016 by Suzie

[Shropshire Lad]

Thanks for that Suzie, I'll get some diodes ordered and have a play.

[Derekm]

Hi I’m interested in using diodes for abc braking with Zimo decoders installed.

 

what diodes do I need and how do i connect them I assume I solder in a line ? And then connect to one rail with break ?

 

help would be appreciated.

[Suzie]

1 hour ago, Derekm said:

Hi I’m interested in using diodes for abc braking with Zimo decoders installed.

 

what diodes do I need and how do i connect them I assume I solder in a line ? And then connect to one rail with break ?

 

help would be appreciated.

Look at post 2 of this thread which has a link to some diagrams of how to make BM1 style braking modules on stripboard.

 

I would recommend that you use UF4001 diodes (suitable for trains drawing up to 2A) or UF5400 (bigger and suitable for up to 6A), but any fast diode will do. 1N4001 diodes are often mentioned but they are not really suitable because they are not fast enough and they mess up the DCC waveform possibly creating some poor response and reliability issues.

 

These BM1 modules just connect in line to the feed of an isolated section of track. Convention is to connect it in line with the left rail, but you can use the right rail just by connecting it the other way round.

Edited September 4, 2021 by Suzie

[Sir TophamHatt]

Although if anyone wants some official BM1 modules, I think I have two in the draw doing nothing.

Happy to pass them on.