Hi.
After my great success in constructing my own digital signals, I have now got an even more crazy idea: A "reduced speed" module.
The idea is to make some sort of electronic device, that enforces loks in its control area to have a reduced max speed. That could be a single block, a station or a shunting area. My vision is to see a train at full speed, slowly decelerate and drive gently into a station, and then slowly come to a complete halt at the platform. The only catch is that I don't want any feedback from the loks, and I certainly don't want to see a PC connected to my layout

One other practical use I see, is to have this speed limit in my shadow station, so trains won't blast full speed in there, and derail before I've had a chance to slow it down.

So how about it. Is this an ambitious but good idea, or am I just downright crazy?

Cool. So now we just need to convince M* to discard the Motorola and mfx protocols, and make the switch to DCC

That is a possibility. I haven't decided on the practical approach just yet. I have two basic ideas:

1. Make small, individual modules, that is more or less integrated with a new version of my signal module. This will be able to control a single block with a single train only.

2. Make a small adapter, that will be inserted between the controller and a booster. The output from the booster will then be speed restricted, and can be used to feed an entire station area (and more).

The first option is by far the most flexible one, and would allow for some very interesting operational aspects. Unfortunately, every module of this type will have to have some power electronics (in effect a mini-booster per block), and they won't be cheap to make.
The second option will cost a real booster, but can feed a large area where you may have had the need for a booster anyway. You will only need one adapter for the booster, and I think that can be built for around $20.

I haven't decided which way to go yet.

It was something along the lines of your LocoNet idea, I had. I was just thinking of using the original M* booster connection.

Are there any documents on the specifications of Märklins booster connection and/or LocoNet somewhere (in public that is)? It may be wise to study the connections/protocols before deciding to go on with this project

Yes,
you've got the links. With your knowledge I suspect LocoNet should be interesting; It's really designed to allow for hobbyists to interfer.

This 'personal edition' is the description intended for this purpose. There is also a possibility for firms to do it professionally, I get the impression that Digitrax are rather encouraging in this, even though, there is a license fee for this I think (not so for personal use).

I think you should look at it, but I'm not sure it's good for this specific problem.

Regards,
Lars

Hi Mikael,

I think your original idea of having a "translation module" inserted between the control unit and the booster is a possible and not too difficult solution.

One problem with this solution is that you would need to have transition segments between the normal and the slow segment, since the commands will not be synchronized between the slow section and the normal section.

Viessmann already makes one. I tried it and it works. The problem I had was with the lok lights dimming. Also, since I have C tracks with the 74460 decoders, there wasn't enough power for the turnouts to work. I had to reroute the wires for the turnouts in the area where I wanted the train to slow down.

http://www.reynaulds.com...smann/temp.asp?item=5216

Are you sure this will work? Both the resistor and the lower voltage?
All of my loks are regulated, and I would guess this counteracts both of these solutions. If I ran unregulated delta or even analog loks, I can see the point.

Hi,
I'm glad to see I'm not alone with this problem!
I'm looking for an inexpensive solution for reducing speed in the shadow station, to avoid derailment, and halter the train on a shorter distance (no much room....).
I started also with a series resistance in the traction power: the results were not good, especially as I have both delta and "digital" locos: it's not easy to find the balance for the resistance value, my delta loco being very sensitive to this parameter.
So I made some current measurement, and saw that, surprisingly, the peak current for the locos are larger when the programmed speed (mobile station) is lower. (Of course, the current is pulsed, and the duty cycle is much lower at low speed and, at the end, the mean current is lower at low speed.)
Here are some measured values:

S600 (delta): low speed 1.5A peak, during 1.5ms. Duty cycle:1/4; high speed 0.6A peak, during 5ms. Duty cycle:4/5
S16 ("digital"):low speed 1A peak, during 1.5ms. Duty cycle:1/4. high speed 0.4A peak, during 5ms. Duty cycle:4/5
(these values are rather approximate for the signal is very "noisy" (there is also low frequency variations) and I don't have a sophisticated scope). But that explains the result: using a series resistor, the voltage drop not only depends on the loco, but is larger at lower speed, leading in some cases to halt the loco, even programmed for medium speed!

I tried then to put a constant drop voltage in the traction power, independant of the loco current: a zener diode. (in fact 2 zener diodes in series, inversed, to get a voltage drop both for the positive and the negative half-wave).
Using 6.8V zeners (warning:>2W), leads to a result acceptable for me:
-For "digital" locos: maximum speed reduced such that the maximum halting distance at the signal is divided by 2.
If the loco is at low speed, the speed reduction seems less, due to load regulation, but the halting distance is of course still lower!
-For delta loco: same as for digital for max speed, but for the extreme lower speed, it stops: I must use the "second" speed step.

Conclusion: far from being perfect, but also quite better than the resistance, and rather good if only "digital" locos are used.
And only 1$ (2 zeners) per district!

Any idea for improving ? [:p]

Fred

Finally I have some news about this idea I've had for a long time:
I have just completed the first prototype of my reduced speed module (only the hardware for now), to see if it was at all possible to make a system powered by the track voltage only, and send a modified signal to a lok. Well.... It was possible
Now I "only" need to write some software for the microcontroller, that will slow down (or even stop) the trains. Unlike Tams similar module, I will try to retain the full control over the loks (except for the top speed). And I don't need a heatsink either

Here is the prototype as it is now. I expect it to be much smaller when I am finished with it (IF I can make it work reliably, that is).

Looks good, wish i had that kind of equipment available..

Michael

HOLY SMOKE. I do believe, I've succeeded.
It required quite a bit of programming to keep F1-F4 in the datastream, and I know now why Tams don't do it. It is far from easy to do so. Anyway, I got it to work, and right now I'm just riding a gigantic rush I got from watching it do exactly what it should.

Here is a video I made of the test. The module is set for limiting the speed to step 4. (10 MB Mpeg1 format):
http://www.ejberg.dk/trains/sig..._speed_demonstration.mpg

This module doesn't need any transition tracks. Just an isolated section with the module inserted between the normal track power and the isolated one.

Edit: Video file changed from Windows Media Video to MPEG1 due to some people having problems viewing it.

No, that is normal for this lok. It does that whenever the speed is reduced. In this test the reduction in speed is quite large, so it takes a long time for the sound to return. However, you should be able to hear the sound come back before the lok exits the section.

Ok, my trains with sound just have more sound when driving slow.
How about MFX, will that work too ?
I'm thinking about many sounds/functions.
Or is it "only" the first 4 that will work ?

Michael

Too bad, just assumed that they would slow down too.

Michael

Very impressive, I hope that you share your design with the rest of us. This is great for station areas!

Don't worry. That brake module works fine with mfx.

And yes, I do plan to make the slow module available for everyone. I just want to make sure it works before I do. It still needs a few features, like how to control the module, so trains can stop completely, and start again when needed.
Would anybody be interested in trying it, before it is finished? If so, I could make the design available, before it is finished.