Author Topic: Applying DC to motor leads when a decoder is installed?  (Read 611 times)

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jagged ben

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Applying DC to motor leads when a decoder is installed?
« on: April 27, 2014, 09:28:42 PM »
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I've been mulling whether it would risk damaging decoders to apply  DC voltage to motor leads while the decoder was installed.

Thoughts?

The reason I ask is that I don't have a DCC system at home (I run DCC at the club), but I would like to be able to spin the wheels, for cleaning purposes, on locomotives with decoders that are difficult or impossible to temporarily remove.       

Jeff AKA St0rm

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Re: Applying DC to motor leads when a decoder is installed?
« Reply #1 on: April 27, 2014, 09:34:12 PM »
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You will fry the chip. You can run your DCC locos on DC. You can use a 9 volt battery if need be but the current needs to run through the chip from the rail or wheels.

peteski

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Re: Applying DC to motor leads when a decoder is installed?
« Reply #2 on: April 28, 2014, 12:30:05 PM »
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Yes, as Jeff says, applying any external voltage directly to the motor while it is also attached to the orange and gray decoder wires will most likely damage the decoder.

But why are you even considering this?  If the analog mode is enabled on the decoder (it is in most cased a factory default), then applying DC voltage to the rail pickup (wheels) will make the motor run.  That is how I very often test and clean my decoder-equipped locos.  All decoders sold nowadays should be capable of running from DC (analog) voltage.  Even all the older decoders I have work with had that capability.  I think that is part of the NMRA standard.  Some model companies tout that their decoders are "dual mode", while in fact all the decoders have that capability.
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mmyers

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Re: Applying DC to motor leads when a decoder is installed?
« Reply #3 on: April 28, 2014, 08:12:52 PM »
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Benn there done that. Don't do it.

Martin Myers

jagged ben

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Re: Applying DC to motor leads when a decoder is installed?
« Reply #4 on: April 28, 2014, 08:54:42 PM »
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But why are you even considering this?  If the analog mode is enabled on the decoder (it is in most cased a factory default), then applying DC voltage to the rail pickup (wheels) will make the motor run. 

I don't have any DC powerpacks that run a decoder properly on analog mode.  I have some old MRC Tech IIIs and I guess they have a fixed PWM setting that screws everything up. 

Also a few of my TCS CN decoders do not respond to analog mode even when programmed for it.

peteski

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Re: Applying DC to motor leads when a decoder is installed?
« Reply #5 on: April 28, 2014, 09:07:00 PM »
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I don't have any DC powerpacks that run a decoder properly on analog mode.  I have some old MRC Tech IIIs and I guess they have a fixed PWM setting that screws everything up. 

Also a few of my TCS CN decoders do not respond to analog mode even when programmed for it.

A 9V battery is a perfect source of DC power - the terminals are even spaced just right for powering N scale wheels.  As far as TCS decoders go, if they have analog running capability (and are properly configured), they should run from a 9V battery. If they don't then there is something wrong with them. IIRC, by default the analog mode is disabled on TCS decoders.
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