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I don't know much about DCC but since I assumed that DCC was a standard I thought that all DCC voltages would be the same. After looking at several manufacturers web sites it seems that the hardest thing to find is a decoder maximum voltage specification.

Decoders seem to be rated according to gauge and amps but not according to voltage (unless gauge IS a voltage standard). If it is a standard, I have not been able to find out what that standard is. I did find a booster that had a 3 way switch for HO/O/G.

Perhaps rather than a DCC variation in voltages the difference may be in the analog DC maximum voltage a decoder can handle but if so I have been unable to find any such ratings. Even in G Scale it is not uncommon to find variances from 18 to 24 volts from one manufacturer to another.

I have three questions:

1, is a decoder limited to a "standard" voltage for a specific gauge?

2. Can a HO decoder be used on a G DCC layout? I'm not concerned about amps - just voltage.

3. If each gauge has a DCC voltage standard, what are those voltages?


I am probably taking the following out of context but I found this and it seems to suggest that the track DCC voltage is 16 volts without reference to any gauge:

"To achieve good sound results SoundTraxx designed their voltage of 16 volts DCC as the recommended maximum DC track voltage for their decoders.

Lenz GmbH has designed their systems for the past 10 years to have a factory default DCC track voltage of approximately 16 volts DCC. We choose this DCC track voltage because we desire to deliver a minimum of 12 volts DC to the motor per NMRA S-9 in both standard DCC mode and in the address 0 mode which is designed to operate non decoder locomotives"

Today I bought a Digitrax DH123D but now I don't know if my LGB MTS 1/2/3 power will burn it up or not.

Am I likely to discover Success or Smoke if I hook it up?

Thanks,

Jerry
 

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Jerry, I'm no expert but I've seen this before:
For DCC, NMRA recommends 12V for N-scale, 14.25V for HO, S, O-scale & 18V for G-scale.

I think you may have some issues with the DH123D, 1.5 amp, decoder in a G scale loco. Not too many G locos can run on such a low amp rating and even if they do, under load, such as pulling rolling stock or going up a grade, it will use more than 1.5 amps. What loco do you want to use the decoder for? Do you know the max amp rating of the motor in that loco?

The voltage, as far as I understand, is not critical to the decoder, as it is just the mechanism for delivering power, however, it sounds like a good question to me and hopefully someone that knows will reply.
 

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Jerry, I use an the Digitrax Ho decoder in the LGB Railtruck with no problem and I've got approximately 22 volts AC coming out of the Digitrax Chief.
 

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Jerry-

I'm glad to see the DCC projects are moving along nicely.

Since many DCC systems are built to NMRA Standards and RPs, it would make sense for you to start your research at the NMRA website. In particular, you should read S 9.1 "Electrical Standards For Digital Command Control, All Scales" (Adopted July 2004):

http://www.nmra.org/standards/DCC/standards_rps/S-91-2004-07.pdf

Of course, only DCC products which feature the NMRA Warrant of Conformance have been certified to this standard. As a result of Digitrax's ongoing feud with the NMRA, don't look for the NMRA Conformance Warrant on your DH123D. Also note, while the LGB MTS I/II/III Central Stations are based upon the NMRA DCC protocol, none of the units carry the NMRA Conformance Warrant.

Remember, some "largescale" decoders experience over-voltage problems when used in conjunction with MTS. One can deduce that some HO/N scale decoders will have the same problems.

Your best bet is to try contacting Digitrax regarding the maximum track voltage of the DH123D. However, don't expect a clear answer.

Best regards,
Bob
 

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The DH123D is one tough decoder. It will work all the way to 22 volts or possibly beyond. I've had several in passenger cars for lighting. The motor output is nice for dimming the main coach lights. I also used one in my crane to drive the motor. I'm running 22 volts DCC.
As to other decoders. Well. The Quasinami shuts down and stops working on 22 volts, does not hurt it though. The HO Tsunami is a different story. It will burn up on the "G" position (22 volts) on my Digitrax system. Took 7 months to get a replacement Tsunami from soundtrax.

In general, I have found that many HO decoders will burn up at 22 volts. So check with the manufacturer unless you just like to before expensive experiments.

I can say that the following Digitrax HO products have been used extensively on my railroad and work fine at 22 volts:
The FX3 HO decoders.
The TF2 and TF4 works fine at 22 volts, I have about 30 of them installed and while the plastic shrink on some of the ones driving four LGB 18 volt bulbs have turned black, they still work. Just be sure to include the 1/4 watt resistor when driving LGB 18 volt bulbs.
All Digitrax SFX sound decoders, work at 22 volts, even the "N" scale one.

PLEASE NOTE THAT ALL OF THE ABOVE ARE USED FOR LIGHTS AND SOUND ONLY. I am NOT using any to drive loco motors.
Since Jerry's question is regarding voltage, I figure all of the decoders I listed above work fine at most "G" scale voltages. Current is a different matter.


Jim...
I am a little surprised that the DH123D decoder works in an LGB rail truck. It can not handle the smaller motor in the LGB field railway locos, but then that smaller 5 pole motor does have a higher stall current than the regular 7 pole LGB motors. I've never tried using the HO decoders with the single motor regular LGB locos, even though the 1.5 amp decoders should be enough. Have you ever pulled any cars with that truck? ...Or stalled it?

If it works in the truck, I bet it would work in a LGB trolley.
 

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Since the LGB rail truck has no couplers, perhaps it works as it has a low current draw. The field locos can pull cars for an increased current load.
 

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Jerry - if you can't find the bipolar capacitor you are seeking you can roll your own from two electrolytic caps and two diodes -

I wrote an article some time ago that includes instructions. Have a look at:




Give Your Engines the Capacity to Ignore Dirty Track


about 1/3 of the way down under "Two Capacitor Circuit"

dave
 

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Hi Bob GROSH,

I emailed Digitrax Tech Service before I started this topic.

I asked them:

"My question is whether the large scale DCC voltage (LGB MTS power via a MTS Central Station 1, 2 or 3) would exceed the capability of the DH123D decoder?"

They responded:

"DH123 is safe up to about 1.5 amps where DH163 is good to 2 amps and maybe a little more.
Happy Railroading
Digitrax"

The subject of my email to Digitrax was:

"Can DH123D be used on Large Scale?"

The fact that some MLSers have used the DH123D on their large scale DCC systems seems to suggest that I can safely use it as long as I do not exceed the 1.5 amp max.

Thanks,

Jerry

Posted By bobgrosh on 07/18/2008 12:07 AM
check with the manufacturer unless you just like to before expensive experiments.
 

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Jerry-

I don't believe Digitrax has thoroughly answered your question.
Your options are:

1. Ask Digitrax the maximum voltage specification of the decoder. Also ask whether the current maximum is further reduced for operating voltages above HO scale.

2. Try one and see if it blows up.

3. Reduce the voltage to the decoder input.

4. Sell the analog sound cars on eBay and add sound directly to the locomotives with a $145 motor/sound decoder. If you also need decoders for your locomotives, this may be an attractive route. Remember, installing the "Koopmann" individual RC filter boards will add significant expense/time to the project, especially if you need to add metal wheels to the sound boxcar.

Best regards,
Bob
 

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Hi Dave,

That is a GREAT IDEA.

It makes perfect sense and it gives me an alternative solution to what had become my primary obstacle.

Thanks,

Jerry

Posted By dbodnar on 07/18/2008 8:34 AM
Jerry - if you can't find the bipolar capacitor you are seeking you can roll your own from two electrolytic caps and two diodes -
I wrote an article some time ago that includes instructions. Have a look at:

Give Your Engines the Capacity to Ignore Dirty Track
about 1/3 of the way down under "Two Capacitor Circuit"
dave
 

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Hi Bob GROSH,

That is exactly the kind of information I have been looking for.

I would guess that LGB's MTS Central Stations 1, 2, and 3 (powered by a 20 VAC 50111 power supply) would put out voltage similar to your DCC system.

Like you I am not intending to power locomotives with the DH123D - just sound systems.

Thank you for your help,

Jerry



Posted By bobgrosh on 07/18/2008 12:07 AM
The DH123D is one tough decoder. It will work all the way to 22 volts or possibly beyond. I'm running 22 volts DCC.

I can say that the following Digitrax HO products have been used extensively on my railroad and work fine at 22 volts:
The FX3 HO decoders.
The TF2 and TF4 works fine at 22 volts, I have about 30 of them installed and while the plastic shrink on some of the ones driving four LGB 18 volt bulbs have turned black, they still work. Just be sure to include the 1/4 watt resistor when driving LGB 18 volt bulbs.
All Digitrax SFX sound decoders, work at 22 volts, even the "N" scale one.

PLEASE NOTE THAT ALL OF THE ABOVE ARE USED FOR LIGHTS AND SOUND ONLY. I am NOT using any to drive loco motors.

Since Jerry's question is regarding voltage, I figure all of the decoders I listed above work fine at most "G" scale voltages. Current is a different matter.
 

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Jerry-

You wrote:
>>>I would guess that LGB's MTS Central Stations 1, 2, and 3 (powered by a 20 VAC 50111 power supply) would put out voltage similar to your DCC system.

I think you'll find the MTS track voltage is significantly higher. Tony's Train Exchange makes a nice meter, the RRampMeter HP Version IV, for measuring your DCC track voltage:

http://www.tonystrainexchange.com/products/tteexclusive_measure.htm

In addition to measuring voltage, it can also measure current up to 18-20A. This is a bit of overkill for MTS, but it is still handy.

Best regards,
Bob
 

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Jerry,

Decoders larger than "N scale" up to large scale should handle 27 volts.. Most manufacturers meet this spec.. Soundtrax is 1 that does not, 22 volts max ( shays with blinking headlites on MTS systems ).. This is from the NMRA standards..

BulletBob
 

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Hello BulletBob,

That is good information to have and answers one of my questions.

I appreciate your assistance,

Jerry

Posted By Road Foreman on 07/18/2008 7:39 PM
Jerry,
Decoders larger than "N scale" up to large scale should handle 27 volts.. Most manufacturers meet this spec.. Soundtrax is 1 that does not, 22 volts max ( shays with blinking headlites on MTS systems ).. This is from the NMRA standards..
BulletBob
 

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Jerry-

You wrote:
I have to admit that I am really surprised to hear that you do not know what the LGB MTS track voltage is.


Please don't put words in my mouth. :)

The output voltage from the MTS central station is not regulated. If you apply a higher input voltage, you get a proportionally higher output voltage. With a 20VAC transfomer input, you will get more than 22V to the rails.

However, if Digitrax won't state whether the DH123D meets the 27V NMRA standard, well, you have no way of knowing whether the decoder can handle the load. So, you are back to my original four options:

1. Ask Digitrax for the maximum voltage specification for the DH123D
2. Try one and see if it blows up.
3. Reduce the voltage to the decoder input.
4. Use a motor/sound decoder

There is certainly nothing wrong with option #2. However, if Digitrax won't provide a clear answer and you don't have the stomach to wager a $15 decoder, use one of the other options. Reducing the decoder input voltage is certainly easy, especially if you can build the Koopmann filter circuit in five minutes. :D

Let us know how you make out with the project.

Best regards,
Bob
 

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Jerry-

Glad to hear you went with option #2. Since the DH123D does not carry the NMRA Conformance Warrant and Digitrax wasn't sharing the decoder specifications, there was no guarantee it could survive exposure to the higher voltage.

You might still consider reducing the voltage to the decoder input.

Reducing the decoder input voltage may be easy to you but I don't have the slightest idea of how to do it and you furnished no information about how it could be done. I am a copy cat who follows helpful instructions when they show me how to do what I want to do. I am not an electronics engineer who knows how to build circuits from scratch.


Contrary to your comments above, I did explain the concept of the MTS Central Station ouput being non-regulated. Lower input equals lower output. I didn't provide a diagram, as the concept is straightforward. You can use another transformer or (back-to-back) diodes - your choice.

Before I started this topic I did not know there was a 27V NMRA standard - after all THAT was the reason why I started this topic.

I appreciate BULLETBOB for giving me the answer to my question as it made my choice to try the Digitrax DH123D decoder without fear of throwing $15 away.


If you read the last page of the NMRA S9.1 document, you found all of the central station and decoder voltage ratings. I felt these would allow you to understand the risk of using the DH123D with your MTS central station. Of course, the NMRA standards are only useful if manufacturers build their products to the specifications.

Best regards,
Bob
 

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Jerry-

A few comments regarding your post.

1. No one in this thread ever asked you to read about the NMRA Conformace Warrant procedure. I simply explained the usefulness of the NMRA Conformance Warrant when I answered your initial three questions.

2. Since you were already adding homebrew circuitry and a Digitrax decoder to your LGB sound unit, I figured a few diodes in front of the decoder was fair game. I didn't realize this violated your "100% LGB power supply and control system" specification. :D If you are planning to add 20 such HO scale decoders, it still might be easier to lower the input to the central station...or the output from the central station. Of course, you don't have to do any of these options if you feel the decoder is safe. It's your money and you can decide whether the risk warrants additional changes. My personal preference is to play it conservative.

3. DCC command stations are typically regulated devices.

4. Transformers are not regulated devices.

You wrote:
I realized and expected that the lowest cost decoder (Digitrax DH123D) would be the weak link in my projects but it took me 3 months before anyone ever told me that such a decoder existed and that I could buy it for around $15 - which was $280.00 LESS than the Massoth XLS decoder that you have been insisting that I should buy.



Again, you are putting words in my mouth. :D

I don't seem to remember insisting you should do anything. I am sorry you have misunderstood my recommendations or alternative solutions to be insistances.

Best regards,
Bob
 

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Bob,

Perhaps "insisting" was too strong a word. Perhaps "echo" or "broken record" might have been more accurate:



rwbrashear Posted (on G Scale Mad Forum): June 08, 2008 01:42 pm

Group: Forum Members
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Jerry-


QUOTE
Does anyone know if any (and which) decoders might feed straight DC voltage to the motors and if there are any plain (cheap) decoders that may have a single function of motor control?


I doubt you will find a cheap decoder that will accomplish your goal of running older 4135s type sound units satisfactorily in analog and digital modes.


QUOTE
Since the locos I am considering adding decoders to tend to be relatively inexpensive locos (0-4-0's & 2-4-0's) that are seldom run it would not be financially practical for me to consider either dual decoders or expensive sound decoders.


QUOTE
I am at a point in life that I do not want to educate myself about MTS/DCC and decoders. I just want to find out the simplest way to use them with the least amount of effort and technical reading (which is Greek to me) - while not giving up any of my analog capabilities.


Jerry, these two constraints, namely, frugality and no desire for technical reading, severely limit your options.

Before deciding that an expensive sound decoder is impractical, why not purchase one to understand the full value provided by such a device? If you really don't want to educate yourself about MTS/DCC and decoders, you will find an eMOTION XLS (or equivalent motor/sound decoder) to be a simple solution, providing:
-easy installation
-easy programming
-analog and digital sound
-analog and digital motor control
-good technical support

Of course, there is a drawback. You will be spoiled by this new 'expensive technology' and the noise coming from your other 4135S modules will suddenly seem painfully inadequate.

And once you have more than eight digital locos on the track, you'll want to upgrade from MTS I. And then you'll want to control turnouts from the same remote. And you'll want 16 sound functions...and bi-directional communication...and...and...and finally, you'll forget about analog!

Best regards,
Bob


As you can see, your former advice of "I doubt you will find a cheap decoder that will accomplish your goal of running older 4135s type sound units satisfactorily in analog and digital modes" turned out to be incorrect (thanks to the Mr. Koopmann's circuit) as I have now been successful in finding exactly what I had been looking for (a $15 decoder that works with my 4135S LGB Sound Systems) PLUS I have been successful in doing it within my stated goals of "frugality and no desire for technical reading."

Best regards,
Jerry




Posted By rwbrashear on 07/19/2008 4:32 PM
Jerry-
A few comments regarding your post.
1. No one in this thread ever asked you to read about the NMRA Conformace Warrant procedure. I simply explained the usefulness of the NMRA Conformance Warrant when I answered your initial three questions.
2. Since you were already adding homebrew circuitry and a Digitrax decoder to your LGB sound unit, I figured a few diodes in front of the decoder was fair game. I didn't realize this violated your "100% LGB power supply and control system" specification. :D" border=0> If you are planning to add 20 such HO scale decoders, it still might be easier to lower the input to the central station...or the output from the central station. Of course, you don't have to do any of these options if you feel the decoder is safe. It's your money and you can decide whether the risk warrants additional changes. My personal preference is to play it conservative.
3. DCC command stations are typically regulated devices.
4. Transformers are not regulated devices.
You wrote:
I realized and expected that the lowest cost decoder (Digitrax DH123D) would be the weak link in my projects but it took me 3 months before anyone ever told me that such a decoder existed and that I could buy it for around $15 - which was $280.00 LESS than the Massoth XLS decoder that you have been insisting that I should buy.


Again, you are putting words in my mouth. :D" border=0>
I don't seem to remember insisting you should do anything. I am sorry you have misunderstood my recommendations or alternative solutions to be insistances.
Best regards,
Bob
 
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