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DCC on DC powered layout?

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  • Member since
    August 2021
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DCC on DC powered layout?
Posted by Mark Kuhn on Friday, October 29, 2021 2:15 PM

Hi folks, will a DCC equipped train run on a DC powered layout? I understand that sounds probably won't work, but will the train run normally in forward and reverse?

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Posted by doctorwayne on Friday, October 29, 2021 3:02 PM

This Broadway Mikado, belonging to a friend, was here for some modifications, along with paint and weathering.... 

It would run only intermittently, but the sound would start, then cut out, then start again, with totally different sounds.

I tried to run it, mainly to see if it could handle a train, but it ran only in a stop & go manner...I wondered if it didn't like the output from the PWM throttle that I use on my DC-only layout.

Wayne

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Posted by gmpullman on Friday, October 29, 2021 3:12 PM

It helps to know exactly which decoder is installed. Some of the decoders are not "dual-mode".

Good Luck, Ed

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Posted by cv_acr on Friday, October 29, 2021 3:12 PM

Mark Kuhn

Hi folks, will a DCC equipped train run on a DC powered layout? I understand that sounds probably won't work, but will the train run normally in forward and reverse?

Usually/possibly.

If the DCC decoder is "dual-mode" it will detect a straight DC power supply on the rails and react to it. It may take an extra volt or two of power to get it going for the electronics, but probably not much.

However, if the decoder does not support "dual mode" it won't function. Most modern decoders do though.

Also, if the DC power supply has a fancy "pulse width modulation (PWM)" feature, the engine may or may not function if this confuses it into thinking there could be a DCC signal on the rails.

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Posted by cv_acr on Friday, October 29, 2021 3:13 PM

doctorwayne
I wondered if it didn't like the output from the PWM throttle that I use on my DC-only layout.

Quite likely.

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Posted by rrebell on Friday, October 29, 2021 4:30 PM

Don't forget that even a dual mode decoder can have the DC mode turned off by adjusting a CV.

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Posted by tstage on Saturday, October 30, 2021 10:49 AM

Lastspikemike
CV29 set to 6 or 7 will have DC enabled. I think you add 32 to disable dual mode (analogue it's called).

Actually, you want to subtract "4" from the value of CV29 to remove analog (DC) operation and make the decoder DCC-only.  "32" adds addresses 128 or higher.

Tom

https://tstage9.wixsite.com/nyc-modeling

Time...It marches on...without ever turning around to see if anyone is even keeping in step.

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Posted by richhotrain on Saturday, October 30, 2021 11:31 AM

CV29 is a multi-function CV. It consists of 8 bits, each of which is assigned a decimal value. For example, bit 0 is represented by a decimal value of 1. Each succeeding bit doubles the decimal value, so bit 1 has a decimal value of 2, bit 2 has a decimal value of 4, etc. Thus, bit 7 has a decimal value of 128.

Each of the 8 assigned decimal values has a unique meaning. 4 of these 8 decimal values are the most important in placing a value in CV29 - - bits 0, 1, 2 and 5.

A bit 0 decimal value of 1 indicates reverse direction. If forward direction is desired, then bit 0 has a decimal value of zero.

A bit 1 decimal value of 2 indicates 28/128 speed steps. For 14 speed steps, bit 1 has a decimal value of zero.

A bit 2 decimal value of 4 indicates DC operation. If DC operation is to be disallowed, then bit 2 has a decimal value of zero.

A bit 5 decimal value of 32 indicates the use of a long address. If a short address is to be used, then bit 5 has a decimal value of zero.

Typically, the decimal value of CV29 is 6 "out of the box", meaning that the loco will run in forward direction, using 28/128 speed steps and DC operation allowed.

Since most DCC users use long addresses when operating, it is most common for CV29 to have a decimal value of 34, 35, 38 or 39.

Rich

Alton Junction

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