Good day all. Okay I have read and read and read some more on DCC. Now lets see if I understand what I read! Common rail wiring for DCC is a no no. So if I have an exsisting DC Cab control layout and want to convert it to DCC, I need to have gaps in both rails, correct? Now if I put a gap in my “common” rail across from the exsisting gap in the other rail I will have 8 different isolated sections. Then I will solder a feeder wire to each one of these new gapped sections, then join them together into one wire, split that one and run in to my 2 cabs as the common wire had previously done. So far so good, I think. Now if I replace 1 cab with a DCC unit and flip all the switches to the “DCC cab” I will have true DCC will I not? Thanks for all replys.
Scott
Sounds good to me but wait for some other opinions.
The “DC-or-DCC” power approach.
Let me see if I understand this:
You cut gaps into the common rail and solder feeders, but then join the feeders into one? Why? Electrically speaking, it’s the same thing. At any rate, you will need to electrically isolate the DC and DCC, in whatever means you accompli***hat. Just make sure you don’t run a train across a gap until both sections are switched for the same power supply.
I plan to use the block wiring approach, but instead of having a common rail, I will isolated both rails and have 2 feeders for each block. These feeders will then go into my DPDT switches for DC/DCC, then the DCC feed ‘IN’ will be on a rotary switch for whichever DCC system I will be using. My layout will be a ‘DCC Demonstrator’ layout, explaining multiple DCC systems.
Brad
The purpose of the gaps is to isolate shorts when they happen…to confine them to a gapped segment…BUT, if all segments are fed by a common bus, as Brad has asked, where is the advantage? Save the trouble and just make the rails solid. The way you describe it, a short on one segment is a short on all of them due to their common bus. Your DCC controller will still spot the short, and shut down the entire system, but maybe not before you fry a decoder.
So, yes, gap the track and feed them as you describe, but you must install short protection between each segment and its contact with the power serving bus. The idea is that a short between two gaps will not be detected by the other segments and the controller because the short protector “got to it” first. The short signal and current draw will not get past the interrupter, so your expensive equipment elsewhere will never know that there is a potentially lethal problem.
An explanation…as I understand it…the more power draw you have on a layout, the closer to the protection limits of the DCC controller and the lethal current that each decoder in all of your in-use locos gets. So, if your DCC system is only good for 5 amps, and you are essentially red-lined with 10-12 sound-equipped locos running trains at once, a short has a very high potential to do serious damage…if I understand Randy Rinker and Joe Fugate. Joe’s cheap and effective solution is, as others do, to gap first, but then install 12 automobile tailights wired in series in the feeders for each gapped segment. When a short occurs, the light bulb takes the current and uses it to light up its highly resistive filament, and saves the entire layout. Better, it saves the decoder in the troubled locomotive.
Did I get that right?
-Crandell
Brad, I am using 2 Atlas selectors for a total of 8 blocks. Essentially 8 DPDT switches, one wire from each block to each switch. I also have several feeders soldered to the common rail and they are joined together into one wire, which in turn is connected to the common terminal of each powerpack. The other terminal of each powerpack is connected to Cab A and Cab B respectively of the Atlas selector. When you say you will run the feeders to each switch, do you mean that you will have, take my example, eight former “common rail” feeders to your DPDT switches? I don’t think I can do this with the Atlas selectors. Yes you are right now that I think about it with reference to cutting the common rail.