New to dcc

[Roman12]

Hi. I have a fixed set up of three concentric circuits with a number of lines running off them and the circuits connected via points.

Up to now the system has been dc but I have been given a couple of dcc trains along with an E-Z Command digital controller. Am I correct in thinking that to run dcc all points will have to be altered?

If I do this can I still run a dc train as the controller has a specific number (10) for this. Also, after altering all the points can I just switch off the dcc controller and revert to running as many dc trains as I did before converting the points.

New to dcc so apologies if these are basic questions.

[Howbi]

Would be very useful if you could post a photo of your layout to save asking you many questions as to it's design and position of points etc.......HB

[RDS]

No problem with basic question Roman, we have all been there!

 

With DCC, the whole layout needs to be live all the time.  Hornby sell some point clips (R8232), that look a bit like office staples.  They are sold in packets of 20 clips.  They 'clip' onto the point and have the allow voltage pass across the point when it is switched (to say a siding).

 

You can still run DC Loco's (using a normal DC controller, or your position 10) with the clips fitted but as the whole layout will then be controlled by the controller, it will not be possible to 'hide' a Loco in a siding because it will move as well.

[Chrissaf]

Lots of questions, let me try an pick them off one at a time in order:

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Am I correct in thinking that to run DCC all points will have to be altered?

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With a DC layout, the layout is split into a number of independent power zones. One zone per DC Analogue controller output. Typically, a power zone will consist of an oval of track plus any directly attached sidings to it. If you have three ovals (concentric circuits) then potentially you will have three power zones connected to three DC Analogue controller outputs. Ideally, each power zone should be electrically isolated from the others. Thus where points are used to make a cross-over connection from one circuit to the other, the track connections between the points that face each other should ideally have insulated rail joiners.

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OK that is a basic over-view of DC Analogue.

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With a DCC layout ALL of the track is live ALL of the time. Thus you would not normally use the insulated rail joiners between the points as per the DC Analogue layout. Not only that, but with Hornby points, one would fit Hornby R8232 DCC point clips to the points to make ALL the routes through the point track work permanently live.

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To further complicate matters. With Hornby track, the actual power to the track connection has to be a DCC compatible version. With DC Analogue, the power track connection contains a suppression capacitor across the rails of the track. If left in circuit, this capacitor will corrupt the DCC digital signal. The capacitor has to be removed for correct operation of DCC.

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So YES in answer to your question, for DCC the power needs to pass through the points on a permanent basis and this usually involves modifying the points or the layout wiring to achieve that.

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But as demonstrated above, it is not just as simple as that. It is not particularly convenient to keep changing back and forth between DC Analogue and DCC Digital on the same layout, due to the differences in the track power requirements of the two control systems i.e. separate multiple power zones (DC) versus one single power zone (DCC). Plus the need for different track power connectors.

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If I do this can I still run a DC train as the controller has a specific number (10) for this.

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The EZ Command user guide is somewhat vague with regard their DC Analogue support feature.

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It infers that you connect a Bachmann Analogue controller into a port on the back OR you use 'Button 10' (see extract from EZ Command user guide below). In both cases it infers that the DCC AC signal is constant on the track. This would mean that using either the add-on controller unit OR button 10, that the EZ Command station is using a technique known as  'DCC Address Zero'.

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There are many posts on this forum advising AGAINST using this Address Zero feature. If you use it, you risk irreparable damage to your DC Analogue loco motors. Some Hornby DCC controllers also support this feature, but Hornby specifically write into their controller documentation that although they support the feature (because it is written into the DCC standard) they advise NOT to use it. Note that Bachmann have also put in a 'damage motor' caveat about using this feature in their user guide (extract above). The Bachmann comment about leaving locos stationary is the relevant comment. It is the leaving the loco stationary that can damage the motor.

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Also, this DCC Address Zero feature will only allow a SINGLE DC Analogue loco to be controlled. Another complication of this feature, is if you are using it to control a single Analogue DC loco, the DCC digital communication is subject to additional timing delays due to way the Address Zero feature works (stretching the zero bit in the digital signal waveform). This means that DCC locos that are running at the same time might not react to DCC commands as quickly as they normally do and some DCC commands might be missed by the DCC loco decoder altogether.

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Also, after altering all the points can I just switch off the DCC controller and revert to running as many DC trains as I did before converting the points.

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Not without reverting all your track power modifications back to the Analogue DC standard first. As stated above, with DCC all of the track is live all the time. So if you just remove the EZ command station and replace it with an Analogue DC one, then you will only be able to control a SINGLE DC Analogue loco because your whole layout will be a single power zone circuit, due to the modifications you will need to perform to make it DCC compatible..

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In Conclusion:

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With three concentric oval circuits, you would be best completely isolating one of them both physically and electrically and dedicate that concentric circuit to the alternative control system. This would depend upon whether the DCC locos you have outnumber the DC ones or whether the DC ones outnumber the DCC ones. In other words, if the DC ones outnumber the DCC ones on a 2 to 1 basis for example, then make two concentric oval circuits DC with the third DCC. If the intention is in the long term to have more DCC locos, then make the third concentric oval circuit DC instead and keep the bulk of the layout DCC controlled. This would also mean that the DC Analogue locos must not be allowed to traverse onto the DCC controlled part of the layout - see next paragraph for why. The DCC locos (ones with decoders fitted) can run perfectly OK under Analogue DC control without issues (but like the DC locos must NOT be allowed to traverse from the DCC section to the DC section - see next paragraph for why). DCC decoders support DC running operation by default as standard (this feature can optionally switched off by changing the value of CV29, but not I believe by the EZ Command station as it is too basic).

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Remember both types of power circuits DC and DCC MUST remain TOTALLY separate both physically and electrically. If the DC track comes into contact with the DCC controlled track you risk irreparable damage to one or both controllers. Trying to drive a loco across any insulated joins between the DC Analogue and DCC Digital track will connect the two controllers together via the loco wheels. Hence total physical isolation is preferred.

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There are also many posts on this forum discussing dual DC / DCC layout working.

[Roman12]

Sorry not at home at present. It's a very basic layout with the three concentric circles connected to each other with a set of points on either side of the setup 

[Roman12]

Many thanks Chrissaf and RDS at last I fully understand the relationship between dc and dcc. Thanks.