dcc question

[Paulali]

I have a dcc layout,but i have a dc class 91,can i run that on my layout with address 00 and still run my other dcc trains at the same time?

[2e0dtoeric]

NO!!! Do not ever put a dc loco onto a DCC layout. The 16v ac 'base' power will fry the motor in seconds!

Why? The motor is designed to rotate in a direction when it 'sees' a dc volltage - show it an AC voltage, and it will try to rotate in both directions at almost the same time. You will hear a loud buzzing noise, followed by a puff of expensive smoke as the motor windings overheat.

-

You can do it the other way around, and run a DCC loco on a dc layout - providing the dc running has not been disabled in each decoder - but of course the sounds and functions don't work - usually.

[Rog RJ]

It doesn't always burn motors out.  I have run one of my old Triang locos successfully on address 0 for quite a few minutes as a test.  This was a couple of years ago but I wouldn't recommend doing so. In any case, you can only run 1 loco with address 0 and no others, due to the way the DCC signal is mangled to enable a non DCC fitted location to run.

 

Again, not recommended.

[Paulali]

thankyou for the reply

[Rog RJ]

..........  DCC fitted location 

 

Should read "DCC fitted loco."

[96RAF]

The answer is yes you can but it is not advised.

What you should never do is let a DC loco stand around on a DCC track. Whilst it is on the move it sees a bodged (biased) DCC signal that tells it which way to run and how fast to go, but when stationary it just gets that warm funny AC feeling. 

Rob

[Paulali]

Thankyou Chris,so much for a very informative answer,you hit the nail on the head,i knew the option was there to address a dc loco,ie adress 00,but i will not be using it,i have seen an option to disable this from the select and that is what i have done,thanks again

[RDS]

I guess it will be around, or even less than £20 to convert it to DCC and then you could run it properly with the rest of your Loco's.

[Chrissaf]

I agree with everybody else.....don't do it.

.

But you're probably wondering why the DCC controller and the DCC standard has a 'zero address' option if everybody is saying don't use it?

.

Answer: A legacy left over from when DCC was new and just getting started. Early adopters had the bulk of their layout as DC Analogue and were introducing DCC slowly. The manufacturers responded and wanted to make their DCC systems as palatable to the DC Analogue user masses as possible. Thus they devised the 'zero address' function. As other's have said, the DCC track signal is an alternating voltage. It is however not true AC but is a bi-polar square wave. The Zero address function works by varying the width of the binary 0 part of the wave form. Above the zero volt line to give a pseudo positive bias voltage and below the zero volt line to give a pseudo negative bias voltage. It is this bias in the voltage that makes a DC Analogue loco go either forward or backward. Manipulating the DCC waveform this way also has a knock on effect in the way DCC locos are signalled by the controller. Due to increased digital signal latency, locos can potentially miss or have to wait too long for DCC commands. The 'zero address' feature, does allow decoder fitted DCC locos to be run on the track concurrently, but it is possible that you might observe unusual behaviours by them. The stretching of the binary 0 part of the waveform increases digital signal latency and slows down the rate at which DCC commands are sent to track. And because in DCC, the track (all parts of the track) is(are) always live, you can only use the 'zero address' to control a single DC Analogue loco.

.

However, when the Zero address DCC waveform bias is neither positive or negative, the DC analogue loco remains stationary but heats up due to the standing DCC alternating waveform. It is this standing stationary that is likely to damage the loco motor windings.

.

Anyway, back to the plot.

.

The manufacturers provided this feature as a compromise more for marketing purposes than technical suitability and somewhat ignored the negative attributes of 'zero address' support. Overtime, the need for legacy support has waned. Many controllers do not now have any 'zero address' functionality as manufactures are aware that it is not an ideal or optimum solution for DC analogue support.

.

In essence it is the old adage, just because you can do something, it does not necessarily mean that it is a good idea to do it. Please do avoid running DC analogue locos on a DCC powered track, and if you do, do not leave them stationary on the track.

.

The discussion points made in this reply are based upon 'Mark Gurries' DCC website. Mark is a member of the NMRA (National Model Railway Association) who devised the DCC standard. You can read his full web article here.

[Paulali]

that is what i am doing RDS,i just wanted to check the loco ran ok,my neighbour has a dc layout,but he is away on holiday,so i couldnt check if it ran well,but yes the 91 will be hard wired

[Fishmanoz]

An option to disable DC Running with the Select?  Unfortunately not so, it requires an adjustment to CV29 (subtract 4 from the default value) and this is one of many things the very basic Select cannot do, even at latest firmware. 

[Paulali]

you can switch off analogue/dc loco support with the select

[Rog RJ]

An option to disable DC Running with the Select?  Unfortunately not so, it requires an adjustment to CV29 (subtract 4 from the default value) and this is one of many things the very basic Select cannot do, even at latest firmware. 

dc running can be disabled in the latest (V1.5) firmware.  It's explained on page 19 of the manual.

[96RAF]

Agreed - it is an option in the Select unit reset procedure.

Edit: - but ... what this does is switch off the controller capability to run an anaologue loco, it does not render each and every loco decoder DC running to off, therefore if such a decoder sees a bad track signal it can still runaway of its own volition.

Rob

[Rog RJ]

Yes, my mistake. As Rob says, it only disables the DC running feature in the Select and not in the decoders. ☹️

[Paulali]

just finished hard wiring the class 91,runs very well,only problem im having is  the coaches uncouple if i run at full speed,i shall be adding weight to the coaches to overcome the uncoupling proplem

you can see the loco running here

[dadad]

Hi there,

 

I was for a while a physics technician at a school, we had a ticker timer that contained a dc electric motor that was connected the ac to oscillate.  The motor was a 12volt permenant magnet type, it had to be run from a transformer 2 volt tapping, of cource one was eventualy connected to the 12volt ac ring main, lots of smoke and a nasty smell.

 

John 

[96RAF]

An option to disable DC Running with the Select?  Unfortunately not so, it requires an adjustment to CV29 (subtract 4 from the default value) and this is one of many things the very basic Select cannot do, even at latest firmware. 

Many things Fishy...??

If I had a magic wand, what are your top three to fix, apart from making it heavier so as to make yours a better door stop.

😉

Rob

 

[The son of Triangman]

Hi Rob dropped you an email about your newly purchased margate HST, the decoder is wired incorrectly.

[96RAF]

Hi Rob dropped you an email about your newly purchased margate HST, the decoder is wired incorrectly.

😀

[Fishmanoz]

Simple Rob, make it into a one-knob Elite - no restrictions on any of loco ID, accessory ID or adjustable CV numbers (three).  But a fourth  would help too - USB connection to a PC allowing RM interface. 

 

If it had had done those things like a real one, I wouldn’t have needed an Elite in the first place, I’d have more room in my bottom drawer, and I have real doorstops anyway. 

[96RAF]

Fishy

1 & 2. I think the 0-99 address limitations are hard wired into the Select DNA. It was probably thus coded originally as a result of only having a 2 digit screen and available PIC chip memory at the time, thus likely not possible to change it now. The range limitation applies to both locos and points so that’s only one wish really.

4. GM already has a very pricey PC connector cable for its PA2 controller so that should be technically possible. USB to Xpressnet. Problem is one end is 5v and tother end is 12v. It would be handy though for use with RM and user updates if possible (that’s number 5 on my list).

3. Being able to change CVs would also allow a simple decoder reset (CV8 to 8). Maybe if CVs 1 to 255 could be changed for any supported value 0-255, that would cover it, although getting the hundreds digit onto a 2 digit screen may be a squeeze.

 

I’ll get the prayer mat out, light a few joss-sticks, adopt the Lotus position and see if I can’t invoke some magic for you. I shall also write a letter to Santa, but I don’t think fairy dust or even Xmas elves can do anything about the address range. Failing that maybe a retro-fit 150mm square of lead sheet inside the case to improve the door stop capability.

Rob