DCC locos on DC power

[checkrail]

Constructing first layout for 40+ years and taking first tentative steps into DCC. Haven't yet quite decided on DCC control system (Prodigy?), but using - pro tem - a Gaugemaster DC controller to test newly acquired locos. This afternoon I fitted my first two loco decoders (I went first for the easy ones with DCC socket in tender - a new Hornby Castle and a 28xx). From my recent crash course in catch up reading I was of the understanding that DCC fitted locos would run as normal on DC systems. However, both these locos now run erratically, particularly at low speeds, juddering and stoppin' n' startin'. They'll then come to a dead halt, not starting again at any voltage until given a prod. Track and wheels are clean, they're well run in, and until this morning were running sweetly at all speeds.

 

Is this to be expected? Will running revert to normal/improve when DCC power source acquired and connected? I have other slightly older locos farmed out for hard wiring of decoders (at some expense of course) and am now a bit worried. Rather disheartened, and almost tempted to take the chips out and stick with DC. But although sound, lights, accessory control etc don't interest me, the ability to attach and detach tail traffic, through coaches etc at my planned Brent-type junction station, without complex 3-way cab control wiring, certainly does.

 

Any advice welcome, before I'm in too deep!

 

John.

[Nigelcliffe]

Control of a chip on DC can be erratic, either because the chip doesn't do a good job on DC, or because the DC controller has some feedback circuit which causes the chip and controller to fight each other for control of the loco. Some chips work better, and some DC controllers will work better.

 

It should bear no resemblance to the quality of running you should see on a DCC system.

 

- Nigel

[roundhouse]

Also bear in mind that some decoders wont work at all on DC. I think its only a few but something to be aware of.

[GoingUnderground]

You haven't said which make and model of decoder you've used.

 

If your DC controller has feedback then turn it off if you can. If you have a High Frequency rail cleaner, such as the Relco, then disconnect it.

 

In cases of erratic running, removing the TV Interference suppression capacitors often cures the problem.

[checkrail]

Perhaps I should just get on with acquiring and installing DCC controller - replies (for which thanks) suggest that all may then be well.

 

In answer to Keith decoders are satandard Hornby 4 function. Gaugemaster U series DC controller has braking simulation module (which I haven't used). Does this constitute a 'feedback' controller?

 

John.

[MrB]

I wouldn't DCC pancake motors, not worth the hassle they'll give you. With DCC the track continuity has to be of a very good standard, so track, pick-ups and wheels have to be spotless!

 

Regards

 

Roy

[10000]

Sorry to disagree on both accounts Roy, but those are 2 of the DCC myths a number of DCC users (including myself) are desperately trying to eradicate...

 

First: it doesn't matter whether one runs DC or DCC, the only way for current to reach the train is via the same 2 rails. You'd find plenty of discussion on this topic here on RMweb, and elsewhere... The pancake motor statement needs some nuance: the (original) Fleischmann motors are a joy in control and will happily be converted to DCC. The types you refer to are the less-then-substandard clones like Lima and Hornby. Those are indeed not worthy of being chipped, so change the motor first before attempting to chip the model.

 

I have found that there is nothing wrong with chipping Hornby Ringfields. I have done some of mine with TCS T1 decoders they run fine on DCC and are better on DC

[Sunnysa]

During my 17yrs of op DCC I have been fitting decoders for hobby shops as well as other people.

 

I have fitted chips to many and varied locos with many and varied motors including Hornby and Lima ringfields with no problems at all.

 

All it takes is a little Cv tweaking (not always) to get good performance.

 

This is the beauty of DCC,it allows the chip to be tweaked to suit the motor.

 

Admittidly some cheap decoders don't allow for very much CV alteration which does make it dificult at times.

 

Cheers

 

Ian

[chaz]

I have had DCC on my O gauge layout for over ten years and I have to agree with some of the comments made above. The track and wheels need to be clean for either DC or DCC, the latter is NOT more sensitive to dirt (In fact if you have room for stay-alive capacitors it can be much less sensitive).

 

I recently took my DJH V2 to an open day run by a local club to give it a run on a large oval. It doesn't get much chance to fly on my 14 foot shunting plank! - it was running on DC. As it has an ESU LokSound decoder fitted it didn't move until the controller was wound up pretty high and never got moving at what I consider V2 speeds. A club member then changed the DC controller for one that gave more volts and the loco got nicely underway - on the front of a rake of red and cream Mk 1s - magnificent. It ran very nicely on the better DC controller, smooth and controllable. As it was the only loco at the event with sound it drew a fair amount of attention.

This was the first time I had run any of my DCC equipped models on DC but the experience suggests that they would be OK. Of course I couldn't get any of the nice sounds (safety valves, whistle etc) to work on DC - and the sound volume was somewhat reduced by the lack of volts (some would argue that's a good thing!).

 

Chaz

[Sunnysa]

You are right Chaz, decoder fitted chips always require extra voltage to operate on DC.

 

The chip usually takes 1-1&half volts to wake it up on DC. Most good decoders will run reasonably well on DC, H & HB chips I don't know.

 

Personally I have more respect for my locos and chips and my enjoyment of running trains to run on DC.

 

Also I believe DCC requires cleaner track than DC is another myth about DCC.

 

All model trains need clean track stay alive or not.

 

Cheers

 

Ian

[chaz]

You are right Chaz, decoder fitted chips always require extra voltage to operate on DC.

 

The chip usually takes 1-1&half volts to wake it up on DC. Most good decoders will run reasonably well on DC, H & HB chips I don't know.

 

Ian

 

I suspect that sound decoders require even more volts, Ian. Reading South West Digital's driving instructions I see that the first thing that happens, once the chip "wakes up", is that the sound goes into its startup mode, which can be quite protracted with a diesel. It then just sits there and ticks over (diesel) or hisses (steam). Even more volts are required to get it to move off.

 

Chaz

[Stevelewis]

Just a point which is not often made, DCC control actually dramatically imroves performance in respect of pickup from track to locos, the fact that there is a constant around 16 volts at 3 or so amps in the track with DCC compared to a variable voltage from around perhaps 3V to 12V max depending on what speed the loco is being required to run at, Means that performance is greatly enhanced.

 

When we changed the Garden Line from Analogue to Digital many years back now the improvement in loco performance was dramatic, and the requirement for track cleaning decreased significantly.

[chaz]

Just a point which is not often made, DCC control actually dramatically imroves performance in respect of pickup from track to locos, the fact that there is a constant around 16 volts at 3 or so amps in the track with DCC compared to a variable voltage from around perhaps 3V to 12V max depending on what speed the loco is being required to run at, Means that performance is greatly enhanced.

 

When we changed the Garden Line from Analogue to Digital many years back now the improvement in loco performance was dramatic, and the requirement for track cleaning decreased significantly.

 

Strictly speaking Steve, what you say about current is not correct. The voltage difference between the rails may be higher with DCC, up to about 18V depending on the system and the PSU, but the current will depend entirely on the load (typically the decoder, the loco motor(s), lights, sound etc). Were you to remove all the locos from the track then, providing there are no short circuits, the current flowing will be zero. I found that even Heljan O gauge diesels, which are often said to draw high currents, only measured at about half an amp and that when slipping stationary - I couldn't get one of these powerful beasts to stall when I was testing it. You may well get 3 amps flowing in your wiring if you have a lot of locos moving simultaneously but the current flowing from rails to wheels and pickups for any single loco is very unlikely to exceed an amp, less than half an amp is much more likely. However that is a technical quibble and is just me being picky about voltage and current - it is true that a higher voltage will help maintain the supply at the contact point between rail and wheel and wheel and pickup.

 

Chaz