How to reduce voltage to the tracks?

[M Graff]

Hi, I have a problem that I know have been dealt with before here, but as I´m a bit "electrically challenged" I wonder if someone could go through it in a pedagogical way .

 

I have the Roco Multimaus system with the original Booster and Trafo from my Lokmaus-2 set.

I have been told that the voltage to the tracks can be as high as 23 volts with this setup!?!

I learned the hard way that some sound decoders is very sensitive to over-voltage (I don´t want to tell you how I know...), and that they should have something like 16V instead?

How do I achieve that? What do I need and how do I connect it? I have heard that some kind of diodes should do it, but how many and what kind?

Would be very happy to get some replies on this.

 

Regards; Michael

[Adrian Wintle]

Here is a circuit that will drop the output about 5V. Adding more rectifiers will drop it further.

 

http://www.atlasrr.com/voltage.htm

 

Adrian

[melmerby]

Hi, I have a problem that I know have been dealt with before here, but as I´m a bit "electrically challenged" I wonder if someone could go through it in a pedagogical way .

 

I have the Roco Multimaus system with the original Booster and Trafo from my Lokmaus-2 set.

I have been told that the voltage to the tracks can be as high as 23 volts with this setup!?!

I learned the hard way that some sound decoders is very sensitive to over-voltage (I don´t want to tell you how I know...), and that they should have something like 16V instead?

How do I achieve that? What do I need and how do I connect it? I have heard that some kind of diodes should do it, but how many and what kind?

Would be very happy to get some replies on this.

 

Regards; Michael

 

Is there no adjustment available for track voltage from the booster?

EDIT Is there a "N" gauge setting for instance that would reduce the output voltage?

That voltage is even on the high side for ordinary decoders.

 

Keith

[M Graff]

Thanks! Are those bridge rectifiers equivalent with these:

Link

Those are 200V 6A with a drop of 3V.

How much reduction would I get with 2+2 as in the schematic? 6V?

Thanks for helping.

[Edwin_m]

When you reduce the voltage make sure to re-do the "coin test" on every piece of track. The voltage drop in the wiring won't reduce with a lower track voltage, and if some of the wiring was a bit marginal before then it may no longer trip out with a short circuit. I'm not going to tell you how I found that out either!

[M Graff]

Is there no adjustment available for track voltage from the booster?

EDIT Is there a "N" gauge setting for instance that would reduce the output voltage?

That voltage is even on the high side for ordinary decoders.

 

Keith

 

No, there is no N-scale adjustment (as far as I know...) and I can´t understand why they have settled for such a high voltage in the first place. Especially as the same DCC-system is being sold by Fleischmann in their H0 and N-scale starter sets , the only difference is that it is grey....

[Pete the Elaner]

When you reduce the voltage make sure to re-do the "coin test" on every piece of track. The voltage drop in the wiring won't reduce with a lower track voltage, and if some of the wiring was a bit marginal before then it may no longer trip out with a short circuit. I'm not going to tell you how I found that out either!

 

The coin test is very crude & relies on deliberately shorting out the system. I would not recommend it. There is a much better way:

Remove the DCC system & connect the + & - on the layout together. Get out your multimeter. Switch it to read resistance & put it across the rails all around. Ideally you should have zero resistance. We don't live in an ideal world, so you woun't quite get zero. Smaller is better though.

[locoworks]

digitrax systems( not the zephyr ) have a 3 possition switch on the front of the units to select N/HO/O&G that is suppposed to give 12/14 and 20 volts respectively. the BIG psu 2012 also has a similar switch to do its voltage out. i wonder if combinations of psu setting and command station setting would result in other voltages? i

[melmerby]

digitrax systems( not the zephyr ) have a 3 possition switch on the front of the units to select N/HO/O&G that is suppposed to give 12/14 and 20 volts respectively. the BIG psu 2012 also has a similar switch to do its voltage out. i wonder if combinations of psu setting and command station setting would result in other voltages? i

 

The Lenz 100 has an electronic adjustment using the handset in half volt steps so also can be used for most gauges, hence my query whether the Roco system (a close cousin?) has also.

 

Keith

[M Graff]

I ask again: Are those bridge rectifiers used in the schematic equivalent with these:

Link

Those are 200V 6A with a drop of 3V.

How much reduction would I get with 2+2 as in the schematic? 6V?

I would like to order them as soon as I can.

Thanks for helping.

[M Graff]

I have now ordered them

As I understand it, if I connect them as per the schematic I will get a 6V reduction in the system (4 x 1,5V = 6).

Does anyone have any data on how much the Roco systems voltage can, or should, be reduced?

Is there any adverse effects on POM if reduced under, say, 16V?

Thanks again.

[Crosland]

Hi, I have a problem that I know have been dealt with before here, but as I´m a bit "electrically challenged" I wonder if someone could go through it in a pedagogical way .

 

I have the Roco Multimaus system with the original Booster and Trafo from my Lokmaus-2 set.

Replace the transformer with a lower voltage one. What is the existing one giving?

 

Andrew Crosland

[M Graff]

I was thinking about that, but after asking around on a Swedish Forum, I was told that the DCC-central (in this case the handheld) needs the voltage it gets from the original transformer?!? in order to work properly...

I didn´t want to argue about it as I thought that in some way, the manufacturer should have some knowledge on what they´re up to . Besides, a new Trafo would set me back at least £30, and in that case I could instead buy one of these:

Huebsch DCC voltage reducer

It costs roughly the same....

The original Trafo puts out 15V and 2,67Ah, wich is what I believe most DCC systems use??

I don´t get why they boost the voltage out from the system however.... 15V should be plenty!

[Crosland]

The original Trafo puts out 15V and 2,67Ah, wich is what I believe most DCC systems use??

I don´t get why they boost the voltage out from the system however.... 15V should be plenty!

The 15V is AC which, when rectified, gives about 20V, hence the high track voltage.

 

try something like a laptop charger, they are usually around 15 - 20V DC. Something from the lower end should give you alower track voltage.

 

I would be surprised if anything in the system *requires* the higher voltage, but I have no direct experience.

 

Andrew Crosland

[Butler Henderson]

I have a two strings of diodes (in opposing directions) in one leg of the track feed from my multimaus which has dropped the voltage to around 14v without any affects on the functionality of the multimaus.

[Taigatrommel]

I have a two strings of diodes (in opposing directions) in one leg of the track feed from my multimaus which has dropped the voltage to around 14v without any affects on the functionality of the multimaus.

 

I did similar, but on both legs of the track feed. I used 20 1N4004s (10 on each wire) in all, giving 10 effective on each wave of the signal. I've stuck them to the left side of the command station and named it "Marvin".

 

 

[Butler Henderson]

1N400x series diodes are only rated at 1 amp - its best to use 1N540x diodes which are 3 amp. The final digit indicates max working voltage which is at least 35 volt so it doesn't matter which ones you actually buy.

[M Graff]

The 15V is AC which, when rectified, gives about 20V, hence the high track voltage.

 

Andrew Crosland

 

Yes, I studied some electrics-books I have and saw that. Thanks.

But after some more studying, I have gotten some more info on HOW high the voltage actually IS on the Multimaus.

There is some that has measured the output with a RRampmeter, and have read out results of 28V!!

That is 6V ABOVE the maximum limit of 22V set by the NMRA.

I can´t for my life understand why Roco would make a DCC system that isn´t following the RP´s and Standards?

 

Problem is in all cases solved!

I have built the recommended voltage reducing circuit, I mounted the 200V 6A bridge rectifiers in two pairs (as per the Atlas page) and mounted them on a steel-plate acting as a cooling fin.

The steam-locomotives with sound did all have to be reprogrammed due to that the wheel-sync was WAY off.

I also had to increase the speed-curves on all locomotives (understandable with the reduced voltage).

I tried the sound decoders I have now, and after several hours of either standing quiet on the layout or standing idling, none of them were even lukewarm!

The rectifiers weren´t warm either!

So in all accounts a very good result. Thanks all for the very good help!