DCC signalling in model railways

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DCC signalling in model railways 07/04/2014 at 06:30 #58515
maxand
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This is one of a series of articles on how to apply DCC (Digital Command Control) to American model railroads. The available electronic solutions are greatly simplified by SimSig's standards but nevertheless this is an excellent article which may give rise to a few new ideas. Model Railroad Hobbyist Magazine is a free publication and you can download back issues or read its archives online.

DCC Impulses: Signaling your DCC pike

Here is a short YouTube video on how DCC works. Unfortunately it turns out to be an ad, but it gives you the general idea.

[video width=425 height=344 type=youtube]lC02g72NMRA[/video]

Last edited: 07/04/2014 at 06:45 by maxand
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DCC signalling in model railways 08/04/2014 at 07:44 #58545
maxand
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As an afterthought, the advent of Surface-mount technology makes it possible to solder very small components, including tiny LEDs much smaller than the ones in the article, directly onto circuit boards. I'm not aware of any off-the-shelf for UK layouts though there may well be some out there. Building SMT circuits is not that difficult with the right equipment, which is becoming cheaper, and miniaturization is very appealing and has many uses. This would allow even 4-aspect colour light signals to be created. Not sure about feather lights though! Something for future modellers.
Last edited: 08/04/2014 at 07:48 by maxand
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DCC signalling in model railways 08/04/2014 at 13:43 #58561
Firefly
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Like These

:-)

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DCC signalling in model railways 08/04/2014 at 14:40 #58562
maxand
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There you go! Note that gallery photos are all O or OO (roughly equivalent to HO) gauge, and none use SMT. However, they claim to support N gauge, though there are no satisfactory photos at this scale. N scale would probably require SMT.
Last edited: 08/04/2014 at 14:42 by maxand
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DCC signalling in model railways 08/04/2014 at 14:45 #58563
Stephen Fulcher
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It would be difficult to get anything in N gauge to look totally realistic due to the small size involved. You only have to see the GPL signal for OO gauge next to the five pence piece to see how small that is, and then consider that it would be half the size again in N.

I did consider building a fully functioning interlocking for OO gauge, but never got round to it due to the significant number of relays that would have been required, and the cost of the numbers of signals that I would have needed for realism. If anyone ever did do this it would look quite impressive however.

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DCC signalling in model railways 08/04/2014 at 16:28 #58573
Steamer
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" said:
There you go! Note that gallery photos are all O or OO (roughly equivalent to HO) gauge, and none use SMT. However, they claim to support N gauge, though there are no satisfactory photos at this scale. N scale would probably require SMT.
N appears to use some sort of fibre-optic arrangement, with the LEDs mounted underneath the signal base and hidden beneath the baseboard:

Picture.

It would be interesting to see what could be done with SMT though. 00 gauge Dot-matrix theatre boxes would look fantastic.

"Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q)
Last edited: 08/04/2014 at 16:28 by Steamer
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DCC signalling in model railways 08/04/2014 at 17:02 #58576
jc92
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you can get realistic looking feathers and GPL's in N, theres no issue there. lookup CR signals (who also do 3A and 4A searchlights)
"We don't stop camborne wednesdays"
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DCC signalling in model railways 09/04/2014 at 05:22 #58593
Hawk777
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Have you seen modern surface-mount LEDs? A quick search at DigiKey shows you can get parts that are just a single millimetre long on the long side at very ordinary prices. Soldering such a beast, on the other hand…

Theatre boxes might be a bit harder.

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DCC signalling in model railways 09/04/2014 at 06:18 #58595
Forest Pines
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" said:
Building SMT circuits is not that difficult with the right equipment, which is becoming cheaper
I have read articles claiming that with some SMT components you can do it at home with a steady hand and a normal domestic oven. I'm not sure I'd risk my girlfriend's wrath if I tried it though!

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DCC signalling in model railways 09/04/2014 at 08:01 #58599
maxand
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In Australia the technical colleges can guide one to the best course. SMT is of course involved in "reworking", a term used to resolder CPUs that have become detached from motherboards, spelling the end of many a fine laptop. To do that requires more expensive equipment than attaching much smaller components, but the principle is the same and I can't help thinking that, like it or not, SMT is the way of the electronics future (until we get to wearable components, conducting polymers, etc.)
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DCC signalling in model railways 09/04/2014 at 17:49 #58626
Lardybiker
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Reworking a board means dealing with whatever components were put on the board in the first place. It might be SMT, but it might not. SMT itself has been around for 15-20 years or so and is what everyone uses these days and why your phone and laptop are so small!! Through-hole parts still exists of course and are still readily available and used for that matter.

Rework can require specialized tools but it depends on exactly what you are trying to rework. It's amazing what a skilled technician can do with just an ordinary soldering iron but though once you start getting into designs that use ball grid arrays then a soldering iron simply isn't going to be much use.....

As for soldering SMT, you don't need a domestic oven (in fact the mere suggestion of using one is downright scary!!). A standard 0603 SMT resistor is doable by hand using an ordinary soldering iron. So is a 0402...just, but its really fiddly. The use of some form of magnifier is definitely required. 0402 though is large by modern day standards too...components get a whole lot smaller than that any anything smaller becomes virtually impossible to do by hand, magnifier or not. If you don't do it by hand, your only option is a pick and place machine and a reflow oven....not cheap.

Of course, you could send your board off to a manufacturer to build it for you. There are those that specialize in prototypes and small production runs. They will have the specialist tools to do whats needed so a theater matrix using tiny LED's is certainly possible. Whether its cost effective or not though is another matter....

You can buy LED as a dot-matrix in a single package. I quick search found lots of them but the smallest is too big, scale-wise, for OO as it's 0.7 inches tall (that's for a 5x7 matrix). Scale-wise that's 1.5 feet tall! I also noted another 5x7 matrix device that's only 5mm x 7mm but the matrix is packaged in an IC-type device that ends up making the entire device 10 x 19mm.

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