Running in locos as DC on DCC Wired Layout

[Junctionmad]

18 hours ago, Crosland said:

 

<sigh>

 

It all depends where you take the reference.

 

An AC signal can have a DC component (an offset). The fact that neither rail goes negative (relative to where???) is completely irrelevant.

 

A loco on a layout has no fixed (e.g. 0V) reference. All it sees are the two rails. At one instant rail A is more positive that rail B. At another instant rail B is more positive that rail A. Current always flows from the more positive side to the other.

 

I will say it again, The current flows from A to B and from B to A at different times in the cycle. The current alternates. It is alternating current.

 

You can argue black is white all you like but I am sorry, you are wrong. There is no need to use terms such as alternating DC or bipoplar DC when AC is the accurate description of the DCC signal.

 

 

 

18 hours ago, Crosland said:

 

<sigh>

 

It all depends where you take the reference.

 

An AC signal can have a DC component (an offset). The fact that neither rail goes negative (relative to where???) is completely irrelevant.

 

A loco on a layout has no fixed (e.g. 0V) reference. All it sees are the two rails. At one instant rail A is more positive that rail B. At another instant rail B is more positive that rail A. Current always flows from the more positive side to the other.

 

I will say it again, The current flows from A to B and from B to A at different times in the cycle. The current alternates. It is alternating current.

 

You can argue black is white all you like but I am sorry, you are wrong. There is no need to use terms such as alternating DC or bipoplar DC when AC is the accurate description of the DCC signal.

 

 

Sadly , you are mixing up voltage and current waveforms 

 

AC applies to current waveforms , it makes no comment on the voltage waveform , even of “ we” use it in common-mans parlance tomean also voltage 

 

Secondly EE’s typically use AC to refer as a shorthand to sinusoidal waveforms , hence we get AC coupled , even though it may not be an alternating current , rather a unipolar sinusoid 

 

Insisting DCC is AC is nonsense , because the signal , both voltage and current is more complex then that , and the “AC “ moniker is not really appropriate

 

unfortunately the term DC gets similarly abused 

 

a DCC VOLTAGE waveform cannot be described as AC , cause the term is meaningless when applied to voltage , it’s not even a sine wave . The correct term is a bipolar ( or unipolar ) waveform. 

 

The current flowing in a DCC track circuit , MAYBE alternating , it’s depends on the rectification applied in the decoding electronics , or it may only half wave rectify , meaning there is no alternating current flowing 

 

hence , while one may level critisms at other monikers describing a DCC waveform , AC is actually the most incorrect form of summation  

 

now “ alternating DC waveform “ is not a common EE expression , but it’s not the first time I’ve come across it , while to the mis-informed , it would look like a nonsense term , it’s important to soerate the term alternating , from the term DC . The term alternating refers to the voltage waveform , it’s an attempt to describe that one signal is the inverse of the other on the track , ie it alternates . 

 

the DC moniker is correctly applied as taken from one track feed , that signal at its resulting current flow is manifestly DC. 

 

Hence the the term is not and attempt to say its a AC DC signal , which would be meaningless 

 

the key takeaway is that AC is a bad moniker to decribe DCC , which is why people don’t use it and the Nmra spec never mentions it 

Edited March 6, 2019 by Junctionmad

[Junctionmad]

17 hours ago, smokebox said:

It's a stream of dc pulses.  The number of pulses per period of time determines how fast the motor turns.  At maximum speed the pulses are virtually uninterrupted dc.

Nope , not right 

[Junctionmad]

1 hour ago, 34theletterbetweenB&D said:

 

 

 

Those are my primary reasons. I first want to see how the mechanism performs without the overlay of DCC. And then repeat with decoder fitted to check that performance is further improved. Sometime it isn't, and no amount of alteration to what CV adjustments are available can amend matters.

 

The DCC decoder in respect of motor supply is just a DC controller, small enough to be onboard. If I am forking over cash above what the old style DC controller costs, I expect more. Sadly there are plenty of decoders on sale that don't deliver the full potential that DCC can offer in motor control. Easily characterised if you can compare the mechanism performance with and without DCC.

Where a loco comes supplied with a fitted DCC chip , it certainly makes no sense to remove the decoder just to achieve what you want 

 

firstky simply running in the mechanism , ( there’s no need to run in modern motors ) can be done under DCC , either with. BEMF or disable BEMF as you desire .  If you monitor relative average DCC current , even though most meters give incorrect absolute readings , you can see if the mechanism is bedding in as the current will fall , you can also in my experience derive more by just listening 

 

the point is , there is no advantage  in running in , to explicitly using DC , and removing a decoder merely to run in on dc , is quite frankly ridiculous.  That’s the point.   For debugging faults , etc it’s of course very useful to have a controllable source  of DC  available as one of the ways to debug is by process of elimination and this means sometimes removing the decoder to verify the underlying circuitry , but debugging and running-in are different undertakings entirely

 

your second point is rather confusing , you might enlighten us as to how DCC decoders can improve of dc controllers as far as motor drive is concerned , since in the history of dc controllers , all the techniques used in DCC decoders have also existed in DC controllers , including PWM, amplitude modulated PWM , BEMF , etc. 

 

what DCC brings is the ability to tailor the integrated DC motor control to a particular motor , rather like having a DC controller per motor , but most people don’t buy DCC for motor control , they buy it to allow prototypical cab control . 

Edited March 6, 2019 by Junctionmad

[Clive Mortimore]

Light bulb moment, to eliminate the need to "run in" using DC and then fitting a DCC decoder so you can run your train on the layout. Why not rewire the layout to DC, sell all those surplus chips and buy another loco with the proceeds. I still don't understand with modern models why there is a need to run them in, by the time they have run in one of the plastic sure gears has gone phuft rendering said loco useless because the manufacturer doesn't have a spare gear. 

 

As for bipolar, lithium carbonate and carbamazepine help with the mood swings but you still need to be on your anti-depressant. CBT also helps.

[SRman]

56 minutes ago, 34theletterbetweenB&D said:

 

 

 

Those are my primary reasons. I first want to see how the mechanism performs without the overlay of DCC. And then repeat with decoder fitted to check that performance is further improved. Sometime it isn't, and no amount of alteration to what CV adjustments are available can amend matters.

 

The DCC decoder in respect of motor supply is just a DC controller, small enough to be onboard. If I am forking over cash above what the old style DC controller costs, I expect more. Sadly there are plenty of decoders on sale that don't deliver the full potential that DCC can offer in motor control. Easily characterised if you can compare the mechanism performance with and without DCC.

True, but because the track voltage remains at a constant level, the power supply to the decoder (i.e. the on-board DC controller) is also more reliable, particularly for slow speed running, and allows somewhat better motor control than straight DC even with the cheaper decoders. Dirty track or wheels will interfere with both analogue DC and DCC, of course, but overall, DCC will give better running in most cases (it would be easy to oversimplify, and leave i at that, but even then, some decoders don't work well with some motors, as many people have discovered the hard way).

[Junctionmad]

6 minutes ago, Clive Mortimore said:

Light bulb moment, to eliminate the need to "run in" using DC and then fitting a DCC decoder so you can run your train on the layout. Why not rewire the layout to DC, sell all those surplus chips and buy another loco with the proceeds. I still don't understand with modern models why there is a need to run them in, by the time they have run in one of the plastic sure gears has gone phuft rendering said loco useless because the manufacturer doesn't have a spare gear. 

 

As for bipolar, lithium carbonate and carbamazepine help with the mood swings but you still need to be on your anti-depressant. CBT also helps.

Running in , IS simply the same as running on your layout , it merely means a process where you ease the mechanical bindings and bed together moving parts by excercising the motion. Where it’s on a rolling road , a test track or a layout doesn’t matter a fiddle. 

 

But many locos do need a period of such running in , my recent experience was with several DCC supplied O gauge steam locos , that ran quite poorly out of the box , but after some decent high speed running in , became noticeably freeer and hence quieter , accompanied by some light lubrication as the running in progressed 

[Junctionmad]

8 minutes ago, SRman said:

True, but because the track voltage remains at a constant level, the power supply to the decoder (i.e. the on-board DC controller) is also more reliable, particularly for slow speed running, and allows somewhat better motor control than straight DC even with the cheaper decoders. Dirty track or wheels will interfere with both analogue DC and DCC, of course, but overall, DCC will give better running in most cases (it would be easy to oversimplify, and leave i at that, but even then, some decoders don't work well with some motors, as many people have discovered the hard way).

PWM based DC controllers were often available and achieved the same thing as a DCC decoder , a DCC decoder has no particular benefits as far as motor control goes , except the ability to tailor the configuration to the specific motor 

 

there were equally many dc controllers that didn’t work well with certain dc motors too, coreless being a case in point , also many pulse based dc controllers caused buzzing and overheating 

 

the fact is DCC decoders can’t offer any additional motor control in general , that can’t be achieved using various forms of dc control , buying DCC in the expectation you will magically get better running is likely to lead to a lot of disappointment. 

 

Of course a DCC decoder will be significantly better at motor control then say a H&M duette , but that’s because the  DCC decoder has sophisticated motor drive methodologies integrated , whereas the H&M is just an antediluvian resistance mat.  The same can be said in comparing sophisticated DC controllers to the Duette !

[Pete the Elaner]

39 minutes ago, Junctionmad said:

Insisting DCC is AC is nonsense , because the signal , both voltage and current is more complex then that , and the “AC “ moniker is not really appropriate

 

More complex than what?

 

AC simply describes a circuit where the supply causes current to flow in both directions. It is bad to assume that AC must always be a sine wave.

Beyond this it could be anything. Square wave, sine wave, saw tooth wave are all forms of AC.

 

The term 'Bipolar DC' which you insist on adding to almost all of your posts is complete nonsense. 'Bipolar' & 'DC' are opposites regardless of where you are reciting it from.

 

[Junctionmad]

35 minutes ago, Pete the Elaner said:

More complex than what?

 

AC simply describes a circuit where the supply causes current to flow in both directions. It is bad to assume that AC must always be a sine wave.

Beyond this it could be anything. Square wave, sine wave, saw tooth wave are all forms of AC.

 

The term 'Bipolar DC' which you insist on adding to almost all of your posts is complete nonsense. 'Bipolar' & 'DC' are opposites regardless of where you are reciting it from.

 

as a EE professional ,with 30 years experience  I know my signal description terminologies thanks 

 

You clearly are mixing up CURRENT and VOLTAGE waveforms, the terms  AC ( and DC) specifically are monikers for CURRENT FLOW 

 

Bi-polar and uni-polar are EE terms typically used in relation to voltage waveforms .  YOU have to also apply custom and practice and context in the use of terminology 

 

firstly simply because  a signal oscillates , does not mean  it is AC  hence 

Quote

Square wave, sine wave, saw tooth wave are all forms of AC.

is simply a corruption of the use of the term AC , because these could easy be unipolar signals and the current does not alternate ( which is teh Key definition  of AC )

 

IN a EE design Lab , terms are bandied about in the context of both custom and practice and the context of the relevant design , hence an EE using the term AC , tends to imply that the signal is a sinusoid and the use of  that term tends to be restricted to Mains, Audio and RF terminologies where largely its is a sinusoid, even if the current docent alternate as in the definition of AC

 

if you are talking about digital circuits, you might refer to periodic signals , as Pulse trains , or DC pulse  trains , or specific modulation or encoding schemes , like FSK etc , ( which is essence also describe the resulting waveform ) 

Quote

Bipolar' & 'DC' are opposites

Im afraid it is you that have the confusion , Bipolar means a signal that crosses OV ( or an arbitrarily system assigned reference point that may not be 0v) , hence  its a comment on the VOLTAGE waveform . That is the custom and practice for the use of bi-polar 

 

IF you view DCC from the reference of the system GND ( which is how we generally tend to describe signals in circuits ( ie from teh perspective of the generator mechanism ) 

 

Then clearly DCC is NOT alternating current, hence the application of the moniker.  The voltage signal at that point again referenced to system GND , is Unipolar .   Hence we could say that at this stage and this reference point DCC is a unipolar DC waveform  ( Unipolar as the voltage is always above system GND, DC as the current is not alternating and "waveform" because its not a static metric ) 

 

Now to convey the point that the other side of the bridge driver is generating a symmetrical but alternative waveform (180 degree phase shift in actuality ), we can attach the moniker " alternating " , Because alternating in this case is a comment on the waveform not the current . We could also attach the term bipolar IF we change the reference point .

 

I made this point at the start , trying to argue DCC is AC, is like arguing that a motorcycle is a car , simply because it has wheels .  DCC exhibits elements of AC waveforms , DC waveforms, bipolar voltage etc , depending on the frame of measurement reference .

 

As facebook says  , " its complicated "  thats my point , arguing  a complex waveform ( a modulated digital derived encoded signal )   ( "More complex than what?") , is the same  as one generated by a 19th rotary generator is frankly ridiculous. I have said that AC is a bad summation ( and no EE would ascribe AC as a moniker, which is why NMRA avoided the term ) 

 

Edited March 6, 2019 by Junctionmad

[Junctionmad]

Quote

Bipolar DC

the term is commonplace and is used to comment on a signal that transitions through a designated Zero point ( which may or may not be actually zero ) and is derived from a DC source.  IN digital engineering the term DC is often appended in such a way , even though the signal is considerably more complex . EEs tend to refer to signals by way of their generator methodologies in the absence of a proper well understood term to describe the waveform 

 

You are trying to argue semantically , removing the context , while an amusing debating tactic, ignores the fact that the terminology used in EE is not all mutually exclusive or  definitive and has to be viewed in the context of the application and circuit being considered 

 

by the way , the term I was commenting about was "alternating DC waveform" which was mentioned by one poster as in the NMRA spec, But I cant find it ( they do use the term Bipolar signal ) 

Edited March 6, 2019 by Junctionmad

[34theletterbetweenB&D]

1 hour ago, Junctionmad said:

...Of course a DCC decoder will be significantly better at motor control then say a H&M duette , but that’s because the  DCC decoder has sophisticated motor drive methodologies integrated , whereas the H&M is just an antediluvian resistance mat.  The same can be said in comparing sophisticated DC controllers to the Duette !

I admire your optimism. The evidence from experiment is that there are decoder designs currently on sale that cannot match in some respects what may be achieved in motor control with a Duette. Competent decoder designs - as expected - much exceed what this example of a simple resistance controller provides, and I very much like this refinement, which fully justifies the extra cost of DCC.

[Clive Mortimore]

1 hour ago, Junctionmad said:

Running in , IS simply the same as running on your layout , it merely means a process where you ease the mechanical bindings and bed together moving parts by excercising the motion. Where it’s on a rolling road , a test track or a layout doesn’t matter a fiddle. 

 

But many locos do need a period of such running in , my recent experience was with several DCC supplied O gauge steam locos , that ran quite poorly out of the box , but after some decent high speed running in , became noticeably freeer and hence quieter , accompanied by some light lubrication as the running in progressed 

Again another DCC myth that new locos need "running in". Normal usage runs them in if needed, wears off the burrs that can cause the noise. Mind you if you expect running in to cure things then you could be giving your new loco an early death.  If the gears are too tight they will wear very fast and if too lose will make a hell of a din and wear unevenly. On noticing that the loco is not performing as expected instead of battering the mechanics of the poor thing inspect them before doing to much damage.

 

It is like reading a 1960s review in the railway Modeller "Will improve with running in".

[Steven B]

Normal usage does do the "running in". Most of my locos run better once some of the chemical blackening has been worn off the wheels through use. However, it's a lot easier doing it on a circle of track than a short shunting plank.

 

As for all the AC/DC comments - sounds like a highway to hell to me....

 

 

Steven B.

[Pete the Elaner]

2 hours ago, Junctionmad said:

as a EE professional ,with 30 years experience  I know my signal description terminologies thanks 

 

 

 

Anyone can post on a forum & claim to be qualified in this or that. The number of times you have mentioned the scientifically incorrect phrase 'bipolar DC' proves that the second part of this statement is clearly wrong, so presumably the first part is too.

 

I have better things to do that continue with this futile bickering. Please continue to live in your world of DC DCC if that makes you happy.

[melmerby]

If you used the term "Bipolar DC" where I worked you would have been met with "What?"

[WIMorrison]

4 hours ago, melmerby said:

If you used the term "Bipolar DC" where I worked you would have been met with "What?"

 

Seems fairly mainstream going by Mr Page and Mr Brin on their Google search engine

 

https://www.google.com/search?q=bipolar+dc&amp;rlz=1CDGOYI_enGB761GB769&amp;oq=bipolar+dc+&amp;aqs=chrome..69i57j0l3.6993j0j4&amp;hl=en-GB&amp;sourceid=chrome-mobile&amp;ie=UTF-8

Edited March 6, 2019 by WIMorrison

[sholidom]

Having written to the manufacturers on the subject the official response is,

'Actually, we don't stipulate this. DC or dcc is fine. This stipulation is being removed from the manuals, as for dcc ready it makes no sense. Models that are not dcc ready and will have hard wired decoders fitted would suffer from invalidated warranties, unless fitted by an authorised installer, therefore should be fully tested (run in) on DC first.'

 

So there you have it!

[Junctionmad]

16 minutes ago, sholidom said:

Having written to the manufacturers on the subject the official response is,

'Actually, we don't stipulate this. DC or dcc is fine. This stipulation is being removed from the manuals, as for dcc ready it makes no sense. Models that are not dcc ready and will have hard wired decoders fitted would suffer from invalidated warranties, unless fitted by an authorised installer, therefore should be fully tested (run in) on DC first.'

 

So there you have it!

I think thats definitive from that perspective , ie if it has a dcc decoder run it in on dcc else DC

Clearly from the manufacturers perspective , the issue is dismantling the loco , not the  issue of DC versus DCC

Edited March 8, 2019 by Junctionmad