Asymmetric DCC

QUOTE What you have to bear in mind though, is that the entire train (i.e. the longest you will ever run) must be in the braking section when the BM1 switches in. You then need to add the required braking distance as well !

Is this necessary if the loco is at the front of the train and enters the section first? I have been doing some tests with a Lenz gold and as soon as the loco reaches the asymmetric bit it starts to slow down. Whether there is a train behind it does not seem to matter in the least.

The ESU 3.0 Lokpilot that I have does not support asymmetic braking. It just sails on through. I have scoured the manual and there is no mention of ABC type braking. There is a mention of Braking Generators which are a different thing altogether.

Zimo support asymmetric braking but the one decoder I have is not at a high enough software level. I am planning to get an MX620R but they are not something you can buy over the counter and with the postal system in the state it's in, I am not prepared to order one and have it "go astray".

I am not convinced by the Lenz gold operation. To be most effective, you need to have the constant braking distance switched on. This also means that every time you switch the decoder to speed step 0 it will take that distance to stop, even if it was doing speed step 1 beforehand. I have been surprised a couple of times when a train I thought was stopped was a long way from where I left it. Moving at speed step 1 is damn near imperceptible on a Hornby A4.

If you disable this feature with F4 to stop the loco where you want it you have to remember to switch it back on or it ignores the asymmetric section. To stop reasonably from the max speed, I reckon I need about 6 feet in OO gauge. This is way too much in goods yards. Since there is only one stopping distance and it is in the decoder, all the automatic stopping sections must be the same length regardless of their position on the track.

The worst thing about the Lenz gold I have is the way it stops from high speed. (step > 100). There's a sudden drop in speed, a slight pickup a slowing down to a slowish speed then a sudden halt. I'm sorry but that's just not good enough. It's fine when stopping from less than 100.

So far I am disappointed by what I have found. I hope that the Zimo is better. Reading Zimo's manual suggests that it is, but I will only believe it when I see it.

Maybe I am expecting too much; maybe I should be shelling out for full computer control; maybe I've got the implementation wrong.

David

David,

The reason the whole train should be in the stopping section is that metal wheels can short out the gap in the rails & cause problems. A couple of years ago we had a test track some 70' long divided into 4 blocks, however, we used a braking module - these work with any decoder & you only need one for even a large layout. We used good old fashioned latching relays, reeds & magnets for the actual switching - at least with these you can always see what's actually happening (or not in the case of a problem).

There is also a method which uses "brake on DC", but again not all decoders work with thsi - basically, to stop the loco you put DC on the track with the polarity arranged for "reverse" running. It is supposed to work, but again the decoders must have "brake on DC" facility.

Instead of a braking module you can use a spare or older DCC controller - you have to set all the adrees'es in use to zero but you can vary functions - for example you could set a smoke unit to "off" whilst braking & stationary. When we tried it some sound decoders could be set to whistle or hoot when moving off.

QUOTE often we get as many people looking at the storage loops
We fall into that category . A couple of years ago there was a very nice Swiss layout at Warley and we spent all our time looking at the storage roads train spotting...

QUOTE Your idea about the short isolated sections should work - go for just over a coach length, just in case any coaches have lighting - I would give it a try !

Thanks for that - I will. I happen to be collecting a rake of Hornby Pullmans. I was considering fitting them with single function decoders some time in the distant future. Then there's the our new Rocos which would really benefit from having their interiors lit....

David

QUOTE (johnnoble @ 12 Oct 2007, 11:45) <{POST_SNAPBACK}>As a newcomer (since a teenager many years ago) I am still at the planning stage and have accumulated several DCC ready locos. Having seen that the Lenz silver and gold decoders offer this feature, I was wondering about its advantages in terms of bringing locos to a halt before a point set against them using their cheap BM1 module with I guess appropriate wiring from the point motor switch. There also seems to be the possibilty of an auto stop at a terminus. Does anybody have any views or is their a better way of acheiving the same end, particularly to avoid derailments at points. Incidentaly all my locos will be steam and I gather that space can be a big issue with for instance the Hornby M7
John,

I have a layout which at the moment uses 7 Lenz BM1's. My 4 locos are fitted with the new Lenz silvers which are suitable for ABC. I have a main 4 platform station which is 60" long, two up and two down. At the end of each platform is a Hornby red/green light. I have made up a circuit board for each light which includes a relay and a BM1.
My control box at the far end of my layout is fitted with a push to lock switch and a bi-colour (red/green) led. The track is suitably cut as per requirements listed with the BM1.
If the control box lamp is red, then the BM1 circuit is open, and the train is stopped at the lights. When pushing the switch on say platform 1, the light on the control box turns to green. At the same time, this switch operates the relay which in turn shorts the BM1, turns the light green, and the train now takes off from the platform.
I have a further two platform country station which is also 60" on the other side of my layout, and this is also fitted with the same circuits on each platform.
One part of my layout goes through a wall and into another area, before comimg back through a tunnel. I wanted to delay its return when necessary, so I fitted another light and circuit in there just before it enters the tunnel.
As has been mentioned, the distanced required to stop, is that set by the 'constant braking distance'. On the Lenz decoders, this depends on the top speed of your train (28 steps), and is already preset. I started with two Vi-train 37's and these required a distance of 60" if left running at their top speed. The distance can be measured by running your train at full speed (28 steps) and then at a predetermind spot, shut the speed down to zero instantly. This is the distance required for the train to stop at the required postion in front of the lights. I found that the first cut in the rail (r/h) needed to be 3" before the start of the platform. The l/h cut can be anywhere after the light. ie the nearest join.
When I purchased a Bachmann class 47, I found that it was overshooting the light because its top speed was higher. It would stop properly when the speed was set to 26. I then programmed CV 5 to reduce its stop speed.

Basically, what I do is to set all engines to full speed. I then act as signal man by changing a light to green, and the train starts up and travels to the next stop where it stops automaticaly at the next light. All my trains run from point to point totally controlled by the lights. If you want a fast train, then all lights on its route are set to green. The benifit is the you are not controlling the trains by the controller - that is not touched at all unless I am shunting the 08, or bringing a goods into the yard. The main operation is purely signal box control of lights and points. If I make a mistake, it is usually a wrong point setting and I am trying to put a train into an occupied station.

The size of the train makes no difference to the stopping distance. I have also run a set of Hornby Pullman coaches with lights. This makes no difference to the system at all.

I have only managed to operate with the trains travelling and entering stations at full speed. I understand that it is possible to program the CV's so that the stopping distance is the same at any speed, but I haven't found at how yet as I have been too busy playing. At the moment, if a train enters at half speed, it stops within a quarter of the distance.

Be wary of other decoders that claim that they can operate ABC. I asked one manufacturer who's decoder made the claim but does not work why, and he stated that only lenz decoders will operate, as Lenz have not yet released the software, and they offered to upgrade free of charge when available.
Hope this helps.

QUOTE Your idea about the short isolated sections should work - go for just over a coach length

I was thinking about this on the drive to see PaulRhb's layout in Bournemouth today. I think I may already have the track wired this way because I completely insulate all six rail ends on points and wire it as a separate section. I am using Peco large radius points which are about a coach length. The track sections I have set up for testing asymmetric DCC start directly after a point. This means that I already have the short isolated section which is one coach long. Apart from not liking the deceleration curve that Lenz use for constant stopping distance, I have not had any problems with my test train of six Hornby Gresleys. Perhaps this is due to the way I wire my points?

QUOTE Alanb: I understand that it is possible to program the CV's so that the stopping distance is the same at any speed, but I haven't found at how
There's a bit you can set in CV51(?). This is where the Lenz implementation starts to fall apart for me. I don't want slow trains to stop several feet from the signal, so I switch the constant stopping distance on. The trouble is, when I do that, any change to speed step 0 triggers the constant stopping distance regardless of how fast the train was travelling at the time. The result is that the train will always travel 50" or whatever when I set it to stop.

My initial plan was to wire BM1s so that a signal or point setting would enable / disable the asymmetric DCC as you have done. However all my platforms are bi-directional and I have discovered that two BM1s active at the same time cancel out the differential signal so nothing stops. I am going to "tweak" the circuit by adding a relay to act as the switch. It can then be controlled by either discrete route setting logic or a DCC accessory decoder which is then set up as part of a route. Since I am building my own BM1s, adding a small relay is not a big deal. I have decided to go with a relay rather than a transistor because a) there is no significant voltage drop across a relay I am not convinced I can come up with the appropriate transistor circuit. I don't fancy the voltage drop across the emitter in any case.

Alanb: I notice you are on 28 speed step operation. Maybe that works better than 128 steps?

David

David,

Your point about bi-directional stopping set me thinking and up into my loft this morning. It is perfectly possible to have bi-directional operation using BM1's.
Wire in two BM1's, one on each rail of the platform concerned at opposite ends. i.e using the RIGHT rail in direction of travel system, you will have a bm1 in circuit at the 'entrance' to the platform, and a gap in the rail at the 'exit' to the platform. In your case, we have two entrances and exits, so I will call them 'travel 1' and 'travel 2'.

--------------gap--------------------------------------------------------------------------------- BM1--------------------
(--- (---- direction of travel - 1 rails

--------------BM1---------------------------------------------------------------------------------gap---------------------

direction of travel - 2 ---) ----)

In a bi-directional system, it is the 'gaps' that control it. If you wish a train to stop in travel 1 direction, then the 'gap' in travel 2 direction has to be shorted, and vice versus. The condition of the BM1's themselves do not affect this. They only control whether the train stops or not depending whether they are shorted or not.

So a simple double pole double throw switch marked 1 - 2 will short out the gap required when deciding which direction the train is arriving from. The switch must ensure that one gap is shorted when the other is open.

Two switches, one for each BM1 will decide whether the train stops or carries on through the station in each direction as normal.
If required, signal lights could be set at each end of the platform and operated via a relay in conjunction with each BM1 as I have.

Thanks for the prompt, I had not thought of this idea before. Hope it is useful. I shall have to find a use myself.

Note,
For anyone thinking of using BM1's, it is not difficult. The only important connection is to ensure that the 'entrance' gap is in the right place, as this decides where the train stops after it has used the 'stopping distance' set. Mine was 3". It is possible by moving rails around to arrange for a 'gap' to appear at a rail join in the right place. You then simply remove the joiner, and replace it with an insulated one. If this is not possible, then a fine hacksaw or hobby cutter can be used. The exit 'gap' is easier, as it can be at the nearest join after the exit to the platform. Again, just remove the joiner and replace with an insulated one. The wire connections to the BM1, can be made anywhere along the rail either side of the 'gap'. I have steel rail with copper joiners, so I soldered them to the nearest joiner. Ensure that the connection marked 1 on the BM1 is before the 'gap' in the direction of travel, and no. 2 after otherwise it will not work.

David, I have assumed that your trains will enter from both directions in the 'FORWARD' mode, as you may be aware that trains do not stop for BM1's when operating in 'REVERSE'. Also, in answer to your question, the train stops as normal whether in 28 steps or 128, as my engines are always set to top speed for BM1 operation

Alan

I hadn't thought of cancelling out the BM1 like that - nice one

As a result of press reports that there appears to be an end to the postal dispute in sight, I have ordered a Zimo MX620R. With a bit of luck I'll have it by Wednesday or Thursday and I can report on how Zimo gets on with asymmetric DCC.

David

My gold reports 61 when I read CV7

David
[/quote]

On the silver direct, and one of the silver 8 pin plug, CV7 reads 78. On the other 8 pin plug bought from another dealer as mine was out of stock reads 72. So must be older stock. On the newly arrived 21 pin silver, CV7 reads 82.

I always read the decoder before putting it into service, as sometimes altering one CV can affect another so I can back check if I get any 'funnies' (and I have !!).

There was a problem with the 21 pin, in that CV 113 and 114 read 255, instead of 40 and 10 respectively. Also, more importantly the train would not stop in ABC even after 52 was set, and CV's 113 and 114 were set as the others were.

I emailed Lenz, and received a reply the next day telling me to reset 113 and 114 as I had already done, and to set CV115 to 10. This was strange, as there is not a CV 115 listed in the book. I set it to 10, and hey presto, it all works fine.

Suggest you email Lenz at '[email protected]'

Alan

Have just received two new Lenz silver 8 pin plug decoders from Hattons along with four Hornby Pullman coaches with lights ( the Venice set).
Excellent service from Hattons, I ordered over the net at 1pm yesterday, and they arrived by courier at 8am this morning. They were offering the courier service at the same price as normal post during the strike situation. That is what I call customer service.

I noticed that Lenz are still using the 06/05 booklet which says the version number (CV7) is 65. But they both read 75 as my last ones did. The silver direct that I bought last month has the booklet date 01/07 with CV7 as 78 which it did read as. So they are up to date there. The new siver 21 pin has a date of 05/07, and both numbers concur (82).

I am going to have to retract my statement that lighted coaches work with BM1's. My original statement was made when I was only running one coach in a rake of four non lighted coaches. Having put the new four coaches on the track this morning, I was dismayed to find that the engine does not stop at the lights. It slows down as though it is going to, then trundles past the red light, and picks up speed as it leaves the circuit.

I have emailed Lenz with the problem as they say that they guarantee to sort out any compatabilty problems with their products. Lets hope so, as I was planning on putting lights in other coaches.

Will post when I have a result.

Alan

QUOTE (alanb @ 16 Oct 2007, 12:49) <{POST_SNAPBACK}>Excellent service from Hattons, I ordered over the net at 1pm yesterday, and they arrived by courier at 8am this morning. They were offering the courier service at the same price as normal post during the strike situation. That is what I call customer service.
Alan

Not related with the main subject of the thread, but I'll second that. Whatever I buy from them I receive it max a week whereas anything I buy from Germany takes a month to arrive and I live in Istanbul/Turkey! Truely excellent service.

Baykal

QUOTE I am going to have to retract my statement that lighted coaches work with BM1's. My original statement was made when I was only running one coach in a rake of four non lighted coaches. Having put the new four coaches on the track this morning, I was dismayed to find that the engine does not stop at the lights. It slows down as though it is going to, then trundles past the red light, and picks up speed as it leaves the circuit.

That's reminds me of something I read somewhere on the Internet, that for asymmetic DCC to work, the number of loads like coach lighting, resistive axles etc has to be limited. I presume this is because the current flow these circuits allow between the two rails tends to reduce the size of the differential between the two rails. Here's an idea - if the lights in the coaches are diodes then maybe running them one way round rather than the other will stop them reducing the differential and so the BM1 still works, or maybe they would just go out altogether.

I think the only way to have lighted coaches working in conjunction with a BM1 is to control the lights with a function decoder. Unfortunately these things aren't cheap (£12?), though maybe the MERG might do a cheaper kit for members?

I also have four of the lit Pullmans. So far they are on a different part of the track, so they don't interfere with the signal, but I'm sure once they are part of the train they will be a problem.

David