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· Just another modeller
9,967 Posts
***Hello Dave

Many make it totally confusing without meaning to do so - sometimes enthusiasm overcomes reality and the core of your question gets buried under well meaning complxity... but sift it through, as overall DCC isn't rocket science, just good consistent wiring and a consistent approach to decoder installation, neither of which is hard to do.

Your important decisions will be brand of DCC and decoder. As simple advice, avoid any brand that also sells trains - they rarely make gear as well or as competently engineered as brands that specialise in DCC controllers. That goes for DCC systems AND decoders. Choice of control system isimportant to get the most intuitive and simple sound operation too

The Jargon can be confusing but its picked up quick enough - the trick is to gain the good details frrom the myriad of answers you will recieve. Feel free to ask anything or if you are not sure how to frame the question, PM me and I'll try to steer you a direct path one step at a time...


The basic principals of wiring are the same DC or DCC, with the greatest difference being the diameters of wire used due to the much higher potential power draw and the resultant voltage drop.... and the need for a systematic approach and consistency in wiring quality for best performance long term.

The change from DC to DCC can be totally painless.

You may need to change nothing at all, but if you have used minimum wire diameters or few points at which power and track meet, then you will very probably have to reinforce the number of points at which the wire feeds to the track if you intend a busy layout.

Initially do nothing other than change control system from DC to DCC. (Before connecting DCC, Disconnect all DC controllers and also disconnect any relco or high frequency type track cleaning devices - these are a no-no on a layout with DCC).

By all means then run a train under DCC for a while to try it out... Then, after you've enjoyed your new DCC controller for a wee while, comes the overall "layout testing" to see if anything might benefit from improvement.

(a) The easiest test is called the coin test.

Take all loco's off the layout. Turn on the DCC system (and all the isolated areas too). With the systems overload light visible to you, short the track every meter or so with a coin. Continue until all areas are checked, including sidings.

If, when you short the track each time, the overload light goes on immediately, then the power feed is probably OK. If it hesitates or seems slower, then add a pair of power droppers at that point.

A second possible and very useful "under power quality check". You need to have an electrical load to really see if the rail voltage will remain stable when you are running several trains.

To simulate this, with the DCC system turned on, take a 12 volt car bulb (like a tail-light bulb is good) and connect it to 2 alligator clips. this should be about a 2 amp load, which is equivalent to say half a dozen active trains all at once.

At various places around the layout, connect it to the track ((just clip onto both rails) and then with a multimeter measure the voltage with the meter set to AC.

The meter cannot actually accurately measure the track voltage as its a high frequency square wave that most meters cannot "see" properly, however it'll be near enough for our needs as all we need to see is the reading it gives so the actual value doesn't matter as it'll be the same if the wiring is all good.

Note the first reading then move the bulb to another place - say a meter apart... check again. Continue until all areas are checked, including sidings. If, with this test, there are no "differences" then the wiring is good. If there ARE differences, then add more "droppers" wherever the voltage is lower.


If you had NOT already started wiring, I'd advise as follows:

Don't scrimp on wire as many do: dedicate the cost of one loco to good quality wire and you will get a layout that runs and performs well. Cut corners and you will have problems.

Wire diameter is specified in square mm , number of strands x diameter of strands or in a "gauge" dpending on where you are in the world. Easiest for UK modellers is the # of strands x diameter.

I strongly recommend stranded wire as better to work with in all cases. Buy a good set of strippers and it will become an easy task - a knife isn't the right tool for stripping cable.

Use as the minimum 32/02 for the main power bus wire (Thats just the pair of wires that distribute the power around the layout) and use something like about 1/3 the weight for droppers. These are shorter wires which should be connected to the power bus at regular intervals - ideally about 1 per meter, but thats not a hard and fast rule. More is better shall we say.

You do not need them operationally but do consider setting up a plan to divide the layout into logical electrical sections so if you need to trouble shoot you can turn off parts of the layout to find the problem AND so you can consciously turn off other parts when you want to - for example, you may have a set of coaches with lights that you'd like to turn off via the track when not in use.

No need for more to add confusion at this stage - just ask as you feel the need for information

Kind regards

Richard Johnson

QUOTE (davehunt @ 25 Jan 2009, 21:30) <{POST_SNAPBACK}>I have done about a years work on a dc setup,and was a complete newcomer to wiring,etc.despite my advanced years. I have sections,a yard with sidings,and a number of points, and the whole thing seems to work. Want to explore the possibilities of sound,etc.and am asking the old boring question about changing from DC to DCC. Is all my hard work to go to waste, and would the change -over be unduly complex to one whose electrical skills prior to this layout were limited to wiring a plug and putting in light bulbs.
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