DCC Questions

[jaguar12]

Please could someone clarify a few questions I have about my switch to DCC.  I've looked about on the forum, but couldn't quite get the answer.

 

I have several Hornby DCC ready locos, that I removed the standard Hornby blanking plate from.  I then fitted an R8249 Hornby decoder and have these operating just fine on my DCC layout.  If I wanted to operate these same locos back on a friends analogue layout, do I have to remove the DCC decoder and put the DCC blanking for them to work on analogue. Regardless, is it safe to put these converted locos on an analogue layout (will I damage the decoder/loco)?

 

Whilst I test old Hornby ringfield analogue locos to ensure they are good runners before converting them, I keep unplugging my Elite, fully disconnecting it from the track and then attaching an old Hornby analogue controller to the track, to see how the locos run.  I also take every single DCC converted locos off the rails as a precaution.  Is this strictly necessary?  I think there is one scenario with analogue and digital that is OK, but one that isn't?

 

When I convert some of my Hornby ringfield  locos to digital, removing the capacitor and soldering in an 8 pin socket to put the R8249 decoder in, if I then want to later sell the loco on as an analogue loco, what do I need to do to allow this to happen? Do I have to remove the socket and resolder the wires and capacitor back?

 

Sorry to ask daft questions, but I don't want to jump into this, without being clear about the facts.

[2e0dtoeric]

Firstly you CAN put a dcc fitted loco on an analogue track, and it will behave just like an analogue loco - UNLESS you have disabled dc running on the decoder.

You will not cause any damage to either the decoder, the loco, or the dc controller by doing this.

What you must NOT do is put an analogue loco onto a DCC track, that will very rapidly destroy the motor!

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Testing a 'new' analogue loco before converting. Yes, you are correct, remove the DCC controller, and either remove or isolate all the DCC loco's, or as soon as you start to turn the speed up, ALL your loco's will shoot off!

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To sell them off as analogue, after you have converted them, just remove the decoder chip, and replace it with a blanking plug. You do not need to replace the capacitor, or remove the socket.

The capacitor is there to reduce tv interference when the motor is running, but as nobody has analogue tv's any more, (they all have digital freeview,  cable or satellite), it is not really needed. If you put an AM radio (unlikely!) near the track, that might pick up the unmistakeable crackly whine.

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You are always wise to ask first, if you can't find a definitive answer elsewhere.

[jaguar12]

Thanks for the quick and thorough reply.

 

I'm really confused though.  I've just tried, and all of my Hornby DCC ready locos that I fitted the R8249 decoder to, don't move at all on an analogue powered/controlled layout.  I haven't knowingly done anything  Is this because to work back on analogue, they need the decoder removing and the blanking plate put back in?

 

Before posting my questions, I have 'briefly' used my Elite Controller on 0000 (as per the manual) to run one analogue loco round on the Elite controlled track.   I purposely didn't let it stand still at any point (with a high pitched noise).  I only ran it at a fair speed. Have I done damage to the loco motor doing this then?

[Chrissaf]

 Is this because to work back on analogue, they need the decoder removing and the blanking plate put back in?

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As Eric has already stated, You DO NOT need to remove the decoder and fit a blanking plug to run a DCC loco on a DC analogue track. You do however have to enable 'DC Operation' in CV29 for DC Operation to work. DC Operation is usually enabled by default on most brand new decoders. But may have been disabled by you, if you or somebody else has been tinkering with the value of CV29 or set as 0 (zero) rather than 6 in the factory

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Use your Elite to read the value of CV29 of your loco(s) on the programming track and compare the measured value with the CV29 calculator on the following web site. You will then be able to see if 'DC Operation' [bit 2 of CV29] is enabled or not.

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http://www.2mm.org.uk/articles/cv29%20calculator.htm

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If the calculator above still confuses you. Read the decimal value of CV29 and post the result back here and someone will tell you if 'DC Operation' is enabled or not.

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Regarding Elite Controller 0000 feature. Just because something is supported doesn't necessarily mean that it is a good idea. Most experienced DCCers will advise not to use this feature as it is not worth the risk of damaging your loco. As long as you kept the loco moving (as you stated) then you probably haven't done any permanent damage. The Controller 000 feature is called "Zero Bit Stretching". You can read more about this feature theory here:

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https://sites.google.com/site/markgurries/home/technical-discussions/dc-loco-on-dcc

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PS - I suspect that the R8249 decoders you have fitted may have CV29 configured with a value of decimal 0 (zero). If they are 0 when you read CV29, then write value 6 to them (but only if using DCC addresses between 001 and 127). CV29 with a value of 0 will disable 'DC Operation', value 6 will enable 'DC Operation' and set speed steps to 128. See the calculator link I gave for a more in depth description of CV29.

 

[Fishmanoz]

Alternatively, and this may be a little simpler, just write 8 to CV8 on the programming track.  

 

This resets the decoder to default configuration which includes DC operation will be enabled (6 in CV29) and the loco will be back on its default 03 address (this will be the clue that the write operation worked) and any acceleration/deceleration values will also be back at default.  You will need to change back to your preferred loco addresses as previously though.  

 

Change all loco addresses to something other than the default of 03 so that 03 is available for testing the next new decoder before changing its address too.

[Phil_Spiegel.]

When referring to 'using an old analogue controller', I would EXCLUDE 'pre-electronic' models such as the 'much-favoured' H&M Safety Minor etc - as these have totally unsuitable outputs - they are not a SMOOTH DC which is what is required for a Dcc-fitted loco to run successfully on 'analogue'.     These old controllers - whether with variable-resistor mats, or the variable transformer of someH&M type,  simply rectify the low voltage AC and produce a 100Hz full-wave rectified sinewave (like a series of camels humps) ... which can peak at well over 24V and drop to zero 100x a second.

The early Pulse-width type of electronic controller - with or without feedback - also had a low (often mains-related) operating frequency, which again allows the voltage to fall to zero 100x a second, and this, as above,  causes the processor on the decoder to have to restart each time the power comes back on (100x second) ... and so it may go nowhere, or somehere very fast, by getting confused!

The SIMPLEST and most reliable method of testing a loco (analogue, or dcc fitted) is with a 9V battery - easy to take to swap meets  if buying locos there - simply hold across the wheels (if they have pickups on both sides) or via a short length of track for old models with only 1 side being picked up per bogie.   A 9V battery gives an ideal smooth output - and if the +ve is to the right wheel, the loco should go 'forward'.  Even a sound decoder SHOULD respond, as all dcc decoders are supposed to be able to operate down to 7V   (Modern 3V processors may allow them to work at just 5V).  Of course, this will not work if dc running has been disabled ... one reason I do not disable it - and I han't needed to since I stopped using a 511  many years ago.

When running a dcc-fitted loco on analogue-dc, do not expect to see any reaction until about 5-7V are on the track ... at this point the decoder processor powerd up, and measures the track voltage to see what direction and speed is requested .... and as it increases toward the nominal 12V, this increases from 0 > 12V to the motor  ... so knob/slider based controllers appear to have a large zero-dead area - it is NOT a fault.

SO NEVER use old- fashioned pre-electronic controllers on dcc-fitted locos (or anything else in my opinion!) ...... buy a new controller (or 9V battery)

Technically, if reverting to analogue - if a capacitor was considered to be required by the original manufacturer  to meet Interference regulations, then it should be reinstated (now they are sometimes built into the blanking plug - the ideal soultion) ... because the laws on interference have not changed !!    Digital TVs can still experience /suffer from interference - but it looks completely different, and at low-levels, can be corrected by the TV decoding process.

(Commercial resellers of 2nd hand electrical goods PROBABLY ought to check compliance before they resell 8-)