# What is the actual output of a DCC Decoder - from a motor perspective?



## rreiffer (Jan 14, 2009)

Hello all,
I was wondering if anyone has scoped out what the output is (or is there a standard) of a DCC decoder?
I see some of the "silent running" decoders are utilizing PWM to control the motor but to any of the decoders actually put out a pure variable DC or are they all PWM?








Thanks everyone...


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## Andre Anderson (Jan 3, 2008)

They all use PWM. This way you get better slow speed control, the motor gets very small bursts of full power and the faster you go the longer the pulses get.


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## Road Foreman (Jan 2, 2008)

Also with PWM you can use the motor kick-back between the pulses for speed ( cruiise ) control.. 

BulletBob


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## steam5 (Jun 22, 2008)

A 'silent decoader' will have a PWM fequency above what we can hear with our ears.


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## George Schreyer (Jan 16, 2009)

They have to use PWM because they could not handle the heat of a linear controller nor do they have the volume for an output filter to convert PWM to DC.


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## benshell (Oct 1, 2008)

Would it be possible to hook up a DCC decoder trackside to power non-DCC locomotives? I mean hooking up the track input of the decoder directly to the booster, and then hooking up the motor output of the decoder to the track. 

I was planning on doing this alternate wiring with some toggle switches, so that I don't have to convert all my locomotives right away and so that I can support guest locomotives that run DC. But since we're talking about this is the PWM frequency from a DCC decoder similar to the PWM output of a traditional PWM power pack such as those from Aristo-Craft?


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## Trains West (Oct 4, 2008)

you could as long as nothing else is hooked to the track 

but depending on your system if you have the loco 00 you can just put the standard dc loco on the dcc track and run it under 00 control .

I have done this at every show our club has done with very good results ... my dcc loco running with a not dcc from another member on the same loop 

in fact it works so well that the club now owns it on dcc system and just hooks it up at the start of the show


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## George Schreyer (Jan 16, 2009)

If you have an adequate "DC" power pack already, then use it. All you need is a simple DPDT switch to switch the whole layout from DCC to DC.


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## Trains West (Oct 4, 2008)

I think he wanted to use the radio throttle


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## rreiffer (Jan 14, 2009)

Thanks all but I believe this is a little off topic, but who am I to talk! Anyway, what I learned here is that the output of a decoder is PWM and not linear. This also helps me look to see if there is such a thing as a decoder amp.


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## George Schreyer (Jan 16, 2009)

Basically, no. You can build one yourself but it is easier to get a decoder that has enough capability to do the job by itself.


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## krs (Feb 29, 2008)

Posted By benshell on 31 Mar 2011 11:18 AM 
Would it be possible to hook up a DCC decoder trackside to power non-DCC locomotives? I mean hooking up the track input of the decoder directly to the booster, and then hooking up the motor output of the decoder to the track. 

I was planning on doing this alternate wiring with some toggle switches, so that I don't have to convert all my locomotives right away and so that I can support guest locomotives that run DC. But since we're talking about this is the PWM frequency from a DCC decoder similar to the PWM output of a traditional PWM power pack such as those from Aristo-Craft? 
As George said - use DC for a DC loco or if your DCC system supports zero-stretching, you can use that to run one non-decoder equipped loco.

Hooking a DCC decoder output to the track to run a DC loco is a lousy idea especially if the loco has any electronics in it.
The motor in the loco is a large inductor, if you drive that with a PWM signal you get back-emf spikes (not the same back-emf that is used by decoders for motor control) and you have a good chance of burning out any electronics in the loco. Or, if you're lucky, the electronics just don't work properly but at least they don't fry.
The PWM output of the Aristo TE had my steam sound going full tilt even when the loco was crawling. With DC the sound worked correctly. 

When the DCC decoder is in the loco, it drives the motor directly and there is no connection between the decoder output and the track.


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## Trains West (Oct 4, 2008)

you are wrong it works just fine .... I do it all the time and never fried anything .... I have even had some things run better on 00 then with a decoder


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## krs (Feb 29, 2008)

Your talking apples and oranges here. 
Running a DC loco with address 00 uses the concept of zero-pulse stretching of the bi-polar DCC signal that is normally on the track with a DCC system. 

What Rich wants to do is to connect the PWM output of a decoder to the track to drive a loco. 

These are totally different signals and also different concepts.


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