Using DCC fitted locos on analogue tracks

[DutyDruid]

OK folks, it's stupid question time...

 

I have always said that I would never go DCC for a variety of reasons but having sat in on a home layout tour on Zoom a couple of evenings back I have started to question my original decision.  

 

So, I have a couple of questions, one of which I have asked in the Kadee Shuffle thread in this forum.  The other one is about the advisability - going forward - of buying DCC fitted locomotives to run on my still analogue test track and Club layouts until I can get around to moving house and then building my "dream DCC home layout".  I have trawled back through about 8 years of threads but failed to find anything that seems to answer the question so I've decided to start a new thread.

 

What is the latest advice please?  Is it safe to run DCC fitted locos on DC control?  Is the answer related to which chips you use?

 

I have heard two very distinct schools of thought over the years, one saying "no way" and the other saying "it's OK", but given that when DCC first got going there was an idea doing the rounds that you could safely put a DC loco on a DCC track and control it as "loco 0", and which I knew couldn't work from the outset, I've decided to "ask the audience" for their up-to-date opinions.

 

TIA

 

Elliott

[Nigelcliffe]

Mostly yes, a DCC loco on analogue control is safe and works.  

 

Now the qualifications around "mostly".... 

1 - if there is a Relco or other High Frequency track cleaning device, then DO NOT PUT DCC loco on track.  You risk the decoder being destroyed. 

2 - depends on the controller.  If its pretty smooth DC, then you're fine.  If there is a lot of higher frequency pulse width modulation "noise" then your decoder may be confused by it.   You'll not damage the decoder, but it won't run.   Some exellent older DC transistorised decoders are very noisy electrically and DCC may not like them.  Its a suck-it-and-see, or ask about specific controllers. 

3 - control will be a bit different.   Turn volts up enough until the decoder comes to life, then the loco will run from then upwards.     

4 - a handful of decoders don't have a setting to allow DC running, so nothing you can do with those. 

5 - if someone has turned off the decoder setting to allow DC running, you need a DCC system to change that setting back on again.  Most decoder defaults come with DC running enabled.  

 

 

[meatloaf]

Bachmann advertise there DCC sound locos as being able to run on DCC. Heres the instructions from my 121 dmu

[DCB]

That's a no for most people then.

Has anyone tried a big capacitor across the output of a feed back controller to smooth it?    The old Triang track I have just sold has capacitors across the rails of a couple of track pieces presumably to stop the arcing and kill the TV interference.

Edited March 6, 2021 by DavidCBroad

[Jeff Smith]

First, my DCC knowledge is limited to using Bachmann On30 DCC and Digitrax decoders with a Digitrax Zephyr controller.  These decoders were dual and ran ok on DC using an old Gaugemaster 100M.

[DutyDruid]

8 hours ago, Nigelcliffe said:

 

1 - if there is a Relco or other High Frequency track cleaning device, then DO NOT PUT DCC loco on track.  You risk the decoder being destroyed. 

 

 

Thanks, and yes - I did know about that one.  Club layout Nictun Borrud (as built) had a Relco and at one exhibition during some "down time" near the end of the first day a trader brought a loco over that a punter wanted see run before purchase, dropped in on the main line and tried to drive it from the controller hanging over the backscene.  It stuttered and then died (can't remember if there was smoke and/or a smell of burning) .  He was furious but at the end of the day neither of us were immediately at the layout at the time and he hadn't asked us if he could do it, if he had we would have told him about the hidden Relco (we already knew this was a problem). 

 

In the end we took the Relco out of the layout, partly to stop it happening again to unsuspecting Club members and partly it because seemed to be able to cause a heap of electrical interference in other electrical equipment on the same mains circuit (like the LED lighting)

 

 

[GoingUnderground]

One thing that Nigel didn't mention was that some DCC decoders which the manufacturer claims will work on DC are very fussy about the "type" of DC. I don't know if it is still true, but ZTC 255, 258 and 4007 decoders will only run on what was described by David Nicholson (a name from the past) at the time that I bought them as "pure DC". He meant a constant DC supply such as you get from a battery or from a DC supply which incorporates a large smoothing capacitor between the rectifier and the throttle knob potentiometer. This may be relevant as the 1950s and early 1960s designs of many integrated transformer rectifier controllers didn't include a smoothing capacitor which means that the DC voltage at the track oscillated at the Mains AC frequency (50 Hertz in the UK) between 0 volts and the voltage set by the potentiometer. I don't know if this issue still applies to current ZTC decoders, or to any other makes.

 

I have used ESU and Hornby decoders with Triang and H&M Duette controllers, and they work whils  the ZTC ones don't for the reason described above (that's how I know about the "pure DC" issue) but I don't do it regularly.

 

DCC fitted locos on DC should be OK subject to the limitations so well described by Nigel earlier, and my own comments above.

 

DC locos on DCC powered track is a very definite NO as there is a real risk of the motor overheating and burning out, especially so when it is sitting at rest on DCC powered track. This applies even if a DCC controller has the "Loco 0" feature to allow you to run a loco without a decoder because sooner or later you'll forget to take the DC loco off the DCC powered track and only remember when the burning smell hits you. Most modern designs of DCC controller do not include "Loco 0" anyway.

[GoingUnderground]

9 hours ago, DavidCBroad said:

That's a no for most people then.  Sounds a bit like asking if a petrol engine will run without oil, yes, but not very well and not for very long.

Has anyone tried a big capacitor across the output of a feed back controller to smooth it?    The old Triang track I have just sold has capacitors across the rails of a couple of track pieces presumably to stop the arcing and kill the TV interference.

Not sure I agree with you about using DCC locos on DC, see my comments above.

 

I don't know how DC feedback controllers work so I can't comment, but I'd have thought the smoothing capacitor should be incorporated into the back end of the rectification circuit so that the output from the "rectifier" was smoothed DC and there weren't any problems when the polarity was reversed to change direction.

 

The capacitors you refer to would have been in the Triang grey standard track suppression track R.107 (not sure about the R.97 power connecting and uncoupling track), and also the Triang/Triang Hornby/Hornby Railways Series 3  R.197, Super 4 R.487, and System 6 R.618 power connecting clips, and in the Triang catenary power mast bases (Standard Track R.304 ,Series 3 R.305, Super 4 X.354)  to suppress TV and radio interference which was a bigger problem back in the days of analogue AM radio and VHF TV. I used to get into trouble with my parents in the 1960s when running my Series 3/Super 4 layout in the loft in the evenings if they were watching TV, but the TV aerial was in the roof as well, less than 10 feet away from the layout, so I don't know how effective the suppression capacitors were.

 

Today's Hornby equivalents, R602 power clip and R8206 power track still include the capacitors which is why they sell DCC versions without capacitors, see https://www.rmweb.co.uk/community/index.php?/topic/158200-z21-issue/page/2/&tab=comments#comment-4348559 and https://www.rmweb.co.uk/community/index.php?/topic/162665-Bachmann-dcc-onboard-and-the-hm2000-controller/ .

[Pete the Elaner]

13 hours ago, DavidCBroad said:

That's a no for most people then.  Sounds a bit like asking if a petrol engine will run without oil, yes, but not very well and not for very long.

Has anyone tried a big capacitor across the output of a feed back controller to smooth it?    The old Triang track I have just sold has capacitors across the rails of a couple of track pieces presumably to stop the arcing and kill the TV interference.

 

Why is that a no for most people? I read Nigel's comment & thought the complete opposite:

 

Feedback or PWM controllers are less common & therefore less of an issue than they used to be.

High frequency track cleaners can be removed without too much difficulty if running DCC-fitted locos is a requirement.

 

 

Small capacitors are good for interference suppression but most electric motors tend to run better at slow speeds with a slightly pulsy supply, so using a capacitor to smooth this out may be counter-productive when running DC locos.

Decoders control the motors directly so these can improve running on DC.

Edited March 6, 2021 by Pete the Elaner
removed a 'not' which naturally changed the meaning of a sentence

[DCB]

OK with a re read am I right in thinking a typical DCC Decoder will not be harmed by the output from a PWM controller, but it wont run the loco either?  Consensus seems to be a Relco will fry the decoder is that   theory or has it been tested? I ask because I have been thinking about using DCC equipped bankers on my DC layout.  Uphill they would work on DCC with the non Decoder fitted train loco(s) working on the single DC address, down they would have to run DC. giving independent control of the banker. 

 

[DutyDruid]

12 minutes ago, DavidCBroad said:

 

Consensus seems to be a Relco will fry the decoder is that   theory or has it been tested?

 

Absolutely known to be fact David.  The Relco (or other HF cleaner for that matter) sees the chip as a piece of dirt it needs to burn off the wheels or track and acts accordingly by giving it a massive HF spike which the chip can't deal with.  I've seen it happen (see my post further up this thread, I had to deal with the fall out).

[pauliebanger]

 

30 minutes ago, DavidCBroad said:

OK with a re read am I right in thinking a typical DCC Decoder will not be harmed by the output from a PWM controller, but it wont run the loco either?  Consensus seems to be a Relco will fry the decoder is that   theory or has it been tested? I ask because I have been thinking about using DCC equipped bankers on my DC layout.  Uphill they would work on DCC with the non Decoder fitted train loco(s) working on the single DC address, down they would have to run DC. giving independent control of the banker. 

 

David,

 

You will have no problem running normally using a feedback controller with ZIMO decoders (few, rare, possible exceptions).

 

Don't use a Relco or similar HF cleaner. Know to cause problems so not worth the risk.

 

However, I'm not sure if your plans are viable as currently stated*. You must not connect a DC and DCC controller to the same tracks simultaneously. Very few DCC controllers now have the Loco 0 option, and no one I know would recommend using it if available. It's an old, obsolescent, feature from the early days of DCC to encourage take up by analogue modellers.

 

*A DC and a DCC equipped loco together on DC analogue will behave pretty much as any pair of DC only locos. I.e. not separately controllable, may run in opposite directions, and /or at different speeds.

 

Best regards,

 

Paul

Edited March 6, 2021 by pauliebanger

[Nigelcliffe]

45 minutes ago, DavidCBroad said:

OK with a re read am I right in thinking a typical DCC Decoder will not be harmed by the output from a PWM controller, but it wont run the loco either?  Consensus seems to be a Relco will fry the decoder is that   theory or has it been tested? I ask because I have been thinking about using DCC equipped bankers on my DC layout.  Uphill they would work on DCC with the non Decoder fitted train loco(s) working on the single DC address, down they would have to run DC. giving independent control of the banker. 

 

 

No,  I said "some PWM controllers".     Example:, I have a Zimo equipped loco which won't run on at least one Pentroller (mine).  But the circuitry inside Pentrollers changed regularly as Stewart Hine developed them, and mine is a slightly tweaked for 2mm example.    I can't say "don't work on Pentrollers" because that's not the case, some of my other locos will run on that Pentroller.  And the "problem" loco will run on other controllers.   So, all that can be said is some DCC locos won't work on some PWM controllers.  

 

Relcos can turn your decoders into blue smoke.  That's not a guarantee of blue smoke, but a reasonable chance.  

 

 

Your proposed running sounds like a disaster zone.   Mixing DC and DCC control systems on the same layout is usually a recipe for blue smoke from controllers.   I suspect trying to bank a train under DC control with a mixture of direct-DC controlled locos and DCC-fitted locos won't work well because of hugely different responses to throttle movements.   

 

 

 

- Nigel

 

[RobinofLoxley]

Surely the OP has the option to buy DCC ready locos fitted with blanking plates. These run normally on DC then need chips putting in at switchover time. This incidentally is what I am doing myself. 

 

Just to clarify I have few DCC ready locos most are DC to undergo conversion  where practical to do.

Edited March 6, 2021 by RobinofLoxley
Additional text

[Dungrange]

3 hours ago, DavidCBroad said:

I have been thinking about using DCC equipped bankers on my DC layout.  Uphill they would work on DCC with the non Decoder fitted train loco(s) working on the single DC address, down they would have to run DC. giving independent control of the banker. 

 

I'm not sure that I understand how you intend to implement this idea, but as others have said, it doesn't sound like a good idea.  How do you ensure that the DCC and DC power are ALWAYS separate?  I know you could feed the uphill section through a Double Pole Double Throw (DPDT) switch, so the section itself can only be either DC or DCC, but how do you ensure that nothing (like a lit coach) is bridging the isolation gaps at either end when you throw the switch?

 

As has been stated, most modern DCC controllers do not have a 'single DC address' because it was never a good idea.  Those older DCC controllers that do have a 'loco 0' control the DC locomotive by altering the DCC output so that there is a potential difference between the rails, which the DC loco will respond to, but it's still being supplied with a DCC waveform, which isn't good for the motor.

 

There is then the issue that a DCC decoder needs a higher starting voltage than an unfitted DC locomotive would.  It would therefore make it rather difficult to speed match your DCC fitted locomotive and your unfitted DC locomotive.  At 6 Volts, the DC locomotive is likely to want to start moving, whereas that's probably not enough to power the DCC decoder: it typically requires about 7 Volts to power the decoder.

 

I guess my question is, if you're happy with DC, why would you want to buy a DCC controller just for banking and risk destroying it if you accidently short the DC and DCC sections.  One of our club layouts, which is DC, uses a banker on some trains.  The train to be banked, stops at the signal, and power to the section is turned off.  The banker is then driven onto the rear of the stationary train. Power is then restored to the section in which the lead locomotive sits and the whole train driven as one into the fiddle yard, where the banker is detached and later returns in the downhill direction as a light engine movement.  It only works with certain combinations of lead locomotive and banker, but operation is quite simple.

 

If what you are trying to achieve is the uncoupling of the banker at the top on the hill, then I'd have thought that the best way to achieve that would simply be to use DC cab control.  When the train reaches the point at which you want the banker to pull back arrange your sections such that the lead locomotive is in one section and the banker in a second section and simply switch in a second DC controller set at a slightly lower speed and turn that down so that the banker stops before it enters the section that the lead locomotive was in.   I'm sure that it would take a bit of practice to get right and there is the risk that you switch in a controller that is set wrongly (direction or speed), but that would be much safer than trying to mix DC and DCC.

[Matt C]

2 hours ago, RobinofLoxley said:

Surely the OP has the option to buy DCC ready locos fitted with blanking plates. These run normally on DC then need chips putting in at switchover time. This incidentally is what I am doing myself. 

 

Just to clarify I have few DCC ready locos most are DC to undergo conversion  where practical to do.

 

 

I would agree with this ? Either buy  DCC ready with a blanking plate or remove the decoder from a DCC fitted and replace With a blanking plate untill you are ready to go DCC.  Just check when buying that it isnt hard wired. You can buy separate blanking plates at no huge cost

[Crosland]

4 hours ago, DavidCBroad said:

OK with a re read am I right in thinking a typical DCC Decoder will not be harmed by the output from a PWM controller, but it wont run the loco either?  Consensus seems to be a Relco will fry the decoder is that   theory or has it been tested? I ask because I have been thinking about using DCC equipped bankers on my DC layout.  Uphill they would work on DCC with the non Decoder fitted train loco(s) working on the single DC address, down they would have to run DC. giving independent control of the banker. 

 

 

Just to echo what others have said, that's a really, really bad idea. You may well destroy either the DCC or DC controller(s) when the locos bridge the between the two sections.

 

[GoingUnderground]

2 hours ago, RobinofLoxley said:

Surely the OP has the option to buy DCC ready locos fitted with blanking plates. These run normally on DC then need chips putting in at switchover time. This incidentally is what I am doing myself. 

 

Just to clarify I have few DCC ready locos most are DC to undergo conversion  where practical to do.

Of course a DCC Ready loco with a blanking plate will run on DC - It has to because it is a DC loco.

 

It would be bizarre, to put it mildly, if a DC loco didn't run on DC. And every DCC Ready loco ever made will come with the necessary blanking plate installed. The only exception might be a secondhand loco where a previous owner has removed a decoder from a DCC Fitted loco and called it DCC ready when they sold it but not replaced the decoder with the blanking plate, or just removed the plate from a DCC Ready loco. If the blanking plate isn't in place in a DCC Ready loco then the loco won't run because there'd be no electrical connection between the pickups and the motor.

 

The description "DCC Ready" tells buyers that there is no electrical path from the wheels through the chassis to one pole of the motor, and instead the connections to the motor are routed through the blanking plate. Remove the plate and the motor is totally electrically isolated from the wheels, chassis and pickups. Older models not described as "DCC Ready" had a connection to one pole of the motor through the chassis which made conversion to DCC much harder for some models as it could be quite difficult to break that direct connection routed through the chassis. This applied to many Hornby Dublo locos, but never to Triang ones where the design of the X.04 motor or the 1950s and '60s motor bogies made them very easy to convert electrically even though there is no interface.

 

The only thing that you have to do to fit a decoder to a DCC Ready loco is remove the blanking plate and fireplace it with a decoder equipped with an interface that matches the interface in the loco. The hard bit can be finding space for the decoder within the bodyshell. But DCC Ready locos nowadays often have a space for the decoder. Fitting a sound decoder is a bit more complicated as the DCC ready loco may not come equipped with a speaker and finding space for the speaker can be more problematical. Also some interfaces in locos, notably the 6 and 8 pin interfaces, do not include connections for the speaker. 

[peach james]

My advice is do not mix DCC and DC on the same layout.  EVER.   UNDER ANY CONDITIONS.  You will destroy something.  You will then get mad at why object let magic smoke out.  And then at yourself because it's really your own fault not anything else's.           (that one was about $300)

 

If you want to run bankers, go DCC.  It's the simple answer to running two locos at different speeds on the same piece of track.  (costs you about $28 for the chip for the 2nd loco...)

DCC Decoders on DC- smooth DC only.  I fried an ESU decoder using a PWM controller (MRC Tech 2-2400).  So, I'd recommend against running DCC chipped locos on anything other than a straight DC (not even pulse power DC) system.  That being said, if it is a reasonable design of PWM, it _should_ be OK.  Just don't get mad if the magic smoke comes out, because you've been warned... (that one was a $100 chip...)
 

DCC Decoders and Relco's- yep, decoder is going to fry.  $28 down the tube...

 

DC on DCC (as allowed by Digitrax, and some others...).  It's really AC.  Do you want to do that to a permanent magnet motor? (not for long, it won't.  Total cost so far with that one is $0)

The answer is that DCC for DCC, and DC for DC, and don't mix the two or likely it will cost a fried chip.

I'd note- I quite often end up with layouts that are mixed...hazard of the job, I'm afraid...as I am the Train & Town Co-Ordinator for a couple of Lego shows, where I am usually the only DCC person...That being said, I also cost each show at 1 chip/day, because someone will do something silly to something of mine, and poof...

[DutyDruid]

14 hours ago, Nigelcliffe said:

 

Relcos can turn your decoders into blue smoke.  That's not a guarantee of blue smoke, but a reasonable chance.  

 

 

nec habemus papam

 

[DutyDruid]

14 hours ago, RobinofLoxley said:

 

Surely the OP has the option to buy DCC ready locos fitted with blanking plates. These run normally on DC then need chips putting in at switchover time. This incidentally is what I am doing myself. 

 

The OP speaks...

Just to clarify, modern locos (and units for that matter) can be pigs to get apart.  There are models that the guy who runs the model shop where I work part time is reluctant to chip because of the risk of damaging some detail parts, and I can attest to having difficulties myself while trying to crew a couple of Bachmann tank locos in the past.

 

Now that I am looking more favourably at DCC because of the advantages it would offer with a largely hidden FY, my current pondering point is whether, is it time to think about consciously switching to buying DCC fitted rather than DCC ready stock.

 

I'm giving the problem of retrofitting what I already have a stern ignoring in the hope of a reasonable lottery win before I need to do it.

 

11 hours ago, GoingUnderground said:

 

Fitting a sound decoder is a bit more complicated as the DCC ready loco may not come equipped with a speaker and finding space for the speaker can be more problematical. Also some interfaces in locos, notably the 6 and 8 pin interfaces, do not include connections for the speaker. 

 

 

Thanks for that thought.  Again, I'm no fan of sound having stood too often behind a layout at a show where one of the adjacent exhibits (a TMD) has had most of the 20 or so locos on it "burning and turning" for the entire weekend.  However, I was mightily impressed by the Bachmann "special" of the sound fitted Blue Pullman that was released 18 months or so ago running on our Club test track.  Again, cound fitting could be an option for me in the fullness of time.

[GoingUnderground]

30 minutes ago, DutyDruid said:

.......I'm no fan of sound having stood too often behind a layout at a show where one of the adjacent exhibits (a TMD) has had most of the 20 or so locos on it "burning and turning" for the entire weekend.  However, I was mightily impressed by the Bachmann "special" of the sound fitted Blue Pullman that was released 18 months or so ago running on our Club test track......

I would agree with you there if it is the same layout that saw as a visitor to one exhibition. It may have been prototypical for a TMD to have most if not all of all the locos running, but it was very wearing on the ears and soon became aggravating, at least to me. Don't get me wrong, I like locos with sound and have some myself, but not en masse like that.

[boxbrownie]

13 hours ago, Mattc6911 said:

 

 

I would agree with this ? Either buy  DCC ready with a blanking plate or remove the decoder from a DCC fitted and replace With a blanking plate untill you are ready to go DCC.  Just check when buying that it isnt hard wired. You can buy separate blanking plates at no huge cost

Or...just maybe the OP may want to buy sound equipped Locos and would get the “standard” sound when running on D.C. and when converted to DCC get the whole gamut of options.

 

Just another option.

 

edit : you beat me to the “sound” option......sound at exhibitions is usually a pain, always too loud and too much, mine at home are always quite quiet, no need for deafening levels, just not prototypical at the relative distances we view our models.

It just adds a little something.

Edited March 7, 2021 by boxbrownie