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Effect of diodes on DCC

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  • Member since
    August 2013
  • From: Richmond, VA
  • 1,890 posts
Posted by carl425 on Thursday, January 8, 2015 5:13 PM

gregc
isn't it possible that half the waveform is sufficient to provide enough power for the locomotive to continue at the last speed it was commanded.

I guess it would be possible.  What scares me though is that the decoder would see something like old school pulse-power.  Who knows what that will do? Decoders are too expensive and too annoying to replace to risk killing one.

 

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  • From: Brisbane Australia
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Posted by Alantrains on Thursday, January 8, 2015 4:54 PM

Thanks everyone,

I think I'll take Carl's advice and short out the diodes.

Alan

Alan Jones in Sunny Queensland (Oz)

 

  • Member since
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  • From: lavale, md
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Posted by gregc on Thursday, January 8, 2015 3:47 PM

the dcc waveform provides two things: power and communication.

while the diodes are more likely to disrupt communication, isn't it possible that half the waveform is sufficient to provide enough power for the locomotive to continue at the last speed it was commanded.

greg - Philadelphia & Reading / Reading

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  • From: Richmond, VA
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Posted by carl425 on Thursday, January 8, 2015 2:18 PM

rrinker
This is Asymmetrical DCC.

Nah, this is Half DCC.

In asymmetrical DCC, there are still positive and negative sides of the waveform, they are just not equal in amplitude.

Alantrains
My question is, will this diode section damage DCC decoders or the motors they are controlling if I run an engine into the dioded section of track?

I wouldn't try it with my decoders.  I don't think they would work anyway.  Follow your first instinct and short them out.  Get some jumpers with alligator clips so you can take them off when you're in a DC mood.

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Posted by retsignalmtr on Thursday, January 8, 2015 2:00 PM

I would think that when a locos wheel bridges the Diode gap the Loco(s) will go, all the way in until the last wheel passes the gap and then not stop. Since Diodes don't block AC, wouldn't the loco move out when the locos direction is reversed? Leds light no matter how they are connected to DCC. 

  • Member since
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  • From: Reading, PA
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Posted by rrinker on Thursday, January 8, 2015 7:11 AM

 A single diode will lop off half of the DCC waveform - the track beyond the diode will only see the upper half or the lower half, depending on the orientation of the diode. If things run, thay will be at half speed. Some more advanced decoders can be programmed to perform various actions when they see this half waveform, like automatically come to a stop (following the momentum setting, not just instantly halting). This is Asymmetrical DCC.

                    --Randy

 


Modeling the Reading Railroad in the 1950's

 

Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.

  • Member since
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  • From: Brisbane Australia
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Effect of diodes on DCC
Posted by Alantrains on Thursday, January 8, 2015 5:42 AM

Hi all,

I originally wired my small layout for DC two cab operation and have now hooked up an NCE Powercab as one cab (Not using the other cab) and it works very well with no modifications to the layout. On some of my dead end sidings I originally put an isolated section at the end with a diode wired so a loco would stop when it went into the section, but could be reversed out.

My question is, will this diode section damage DCC decoders or the motors they are controlling if I run an engine into the dioded section of track? I know DCC puts an alternating current to the track and I don't expect the diodes to have the same effect on a DCC loco as a DC loco, but I wonder what effect they do have. 

I'm sure I will accidently run a DCC engine into one of these diode sections one day and was thinking I should short out the diodes, but I ocassionally revert to running the whole layout on just DC and the diode sections work very well then.

TIA

Alan

Alan Jones in Sunny Queensland (Oz)

 

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