Hi All,
I want to run my layout as DC and DCC at different times. I keep hearing that I would need a DPDT between the track and my two controls (DC and DCC), but I've just been reading up on what DPDT means (along with SPST, SPDT and DPST) and I cannot see how the situation needs double pole instead of single pole.
I understand SPDT to mean that the switch "turns one thing off and another thing on", which seems to me exactly what's wanted -- turn the DC off and the DCC on. The DPDT is for when you want to "turn two things off and two things on". But everywhere I research setting up a layout this way the reference is always to DPDT, not SPDT. Is that because the "two things" are the two rails? If not, I don't get it.
Electrical is not my forte and will be a challenge, and I'm a spanking tyro. Lot's to learn. Any help appreciated. Thanks,
-Matt
Seattle, Washington
Modeling a pseudofictitious Pacific Northwest traversed by SP&S, GP and NP power, somewhere in the days of late steam and early diesel.
Returning to model railroading after 40 years and taking unconscionable liberties with the SP&S, Northern Pacific and Great Northern roads in the '40s and '50s.
You need a double pole switch. I would prefer centre off.
A single pole switch has a post for one wire in, and one wire out.
A double pole double throw has six post to attach wires to. In your use, two on one side for input, two on the other side for input, and two in the centre for output to the track.
You would also be wise to turnoff the system you don't want to use, throw the switch, and then turn on the system you want.
crossthedogElectrical is not my forte and will be a challenge, and I'm a spanking tyro. Lot's to learn. Any help appreciated. Thanks,
Matt, welcome to the forums! Your first posts are moderated, so they will not appear right away. After several posts, things will be normal.
I'm like you. I had to read and follow directions when working with the electrical part of the layout. Thankfully, there are a lot of helpful people on this forum.
Let us know how your layout progresses.
York1 John
I asked my doctor if I gave up delicious food and all alcohol, would I live longer? He said, "No, but it will seem longer."
The reason for 'double pole' is that you're interrupting both wires to the track, even if your layout has been wired 'common rail'. That foolproofs the connection.
As noted, the double throw part of the switch (and yes, you want a distinct position for center off "isolated") is to switch this two-wire connection between two things. Normally the center contacts would be power/data and the two switch positions would go to things drawing power. Here you have just one thing being powered (the layout main bus) and two power sources, so you wire 'backward' with the track-power outlets from the two controls connected to the outer sets of terminals and the feed to the layout in the middle... the electron flow doesn't care which way it goes through the contacts.
Interestingly, in the early years of house wiring, wall switches worked this way (it is called 'four-wire'). In 1937 this was made illegal for new construction in favor of hot-side-only switching -- cheaper to build the switches, you know. With four-wire, the fixture(s) controlled by a switch are completely isolated... with three-wire only one side is. The "logic" was that someone ASSuming four-wire without checking might get shocked if there were stray potential on the neutral (which happens all the time) and we couldn't have that, could we?
Shades of denaturing ethanol with methanol to dissuade people from that ol' demon alcoholism...
I'd just add that when I did this, I used a Center-Off DPDT switch. It's nice in some situations (derailment causes a short for example) to be able to cut off all power to the track, rather than just switch it from DC to DCC.
I use a DPDT Relay to switch from DCC back to DC operation. I wire the relay coil to the DC Power Pack accessory connections. Normal operation is DCC, (DC Power Pack off) when I turn on the DC power pack it powers the relay automatically switching the track from the DCC controller to the DC power pack.The DC power pack accessory output is normally AC, you can use an AC relay but an AC relay has a bit of hum, a DC relay doesn’t. I use a chip rectifier (DB107) to convert the AC output to DC to power the coil on the DC relay. Mel My Model Railroad http://melvineperry.blogspot.com/ Bakersfield, California I'm beginning to realize that aging is not for wimps.
wjstixI'd just add that when I did this, I used a Center-Off DPDT switch. It's nice in some situations (derailment causes a short for example) to be able to cut off all power to the track, rather than just switch it from DC to DCC.
Also, using a center off DPDT toggle guarantees that the circuit "Breaks Before Makes", so there will never be a time when both DC and DCC are applied, even for a split second.
-Kevin
Living the dream.
OvermodInterestingly, in the early years of house wiring, wall switches worked this way (it is called 'four-wire'). In 1937 this was made illegal for new construction in favor of hot-side-only switching.
I was under the impression that four wire switches were only used in certain areas of the country where there was no "neutral" wire in house wiring, but two "live" wires that were out of phase, kind of the way 240 volt dryer wiring works.
As electrical code was standardized nationwide at 120 V 60 H the practice of only interrupting the "hot" wire became the way switches were constructed.
Can you imagine the time when local power providers had different voltages, frequency, and sometimes even DC supplied as house utility?
Thank goodness for the NEC.
Which switch? THis one!
https://www.amazon.com/AXLIZER-Electricity-Experimental-Simultaneous-Connections/dp/B08RHZF4FM/ref=sr_1_16?dchild=1&keywords=knife+switch&qid=1614195592&sr=8-16
It is physically impossible to get DC and DCC togehter if this is the switch used to isolate the two,. The layout is either goign to be all DC, or all DCC.
Plus it looks cool.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
rrinkerWhich switch? This one!
SeeYou190I was under the impression that four wire switches were only used in certain areas of the country where there was no "neutral" wire in house wiring, but two "live" wires that were out of phase, kind of the way 240 volt dryer wiring works.
At that time the house was wired with white (very faded and dirty!) and black fabric wire, all with porcelain and brass 4-wire switches, and all the white wires came down to a big copper bus. There was 240 for stove and dryer on a completely separate set of wires, although I was too young to take note of how the meter was wired in and the service panel was extensively rebuilt with breakers about the 8th time certain fuses cooked off...
Now, the house had been converted to gas heat (with a circ pump so old the makers had no record of what was on its data plate) and had the Cullinan Diamond of early sealed-pane insulating windows, so it is possible that the electrical system had been rebuilt to grounded neutral later. We were promised the house blueprints and construction records but never got them.
OvermodMine was built starting 1914, construction delayed by the War, finished 1919.
My oldest daughter just gutted a 115 year old Queen Anne Victorian.
She sent me pictures of some of the wiring and plumbing they found in the walls. Apparently the house had been rewired and repiped at least twice each. Some of the original components had never been replaced.
Lastspikemike Be VERY careful that you CANNOT inadvertently leave ANY DC locomotive on DCC powered track EVER under ANY circumstances.
Be VERY careful that you CANNOT inadvertently leave ANY DC locomotive on DCC powered track EVER under ANY circumstances.
TheFlyingScotsman Lastspikemike Be VERY careful that you CANNOT inadvertently leave ANY DC locomotive on DCC powered track EVER under ANY circumstances. I am DC only but have pondered this just to try out DCC, so I am curious what would happen if the above took place?
I am DC only but have pondered this just to try out DCC, so I am curious what would happen if the above took place?
DC engines are designed to run on variable 0-12 volts of DC power. More power, faster speed. DCC has a constant 14V AC (or thereabouts) on the track. The high AC power could damage the DC motor if left that way long enough; if nothing else, the engine would go very fast...at least for a while.
Conversely virtually all recent (last 10-15 years) decoders are 'dual mode' so can work on DC or DCC power.
DC loco sitting on DCC track won't take off - it will sit there and buzz until eventually the motor overheats. Digitrax (and maybe still Lenz) can sort of runa DC loco by altering the DCC waveform. it will be noisy and depending on the loco may or may not work very well.
The Bachmann EZ Command will run a DC loco on stretch zero bii as well as the MRC Command which I use to have some years ago with five throttles. All on ebay. Throttle one was for DCC or a DC loco. I use to runder drive 4-4-0's with N scale decoders and a Winans Camel, DC as a pusher. Yes it buzzed. Open frame motor with fluwheel and mator armature had patitions on it to be more efficient. Roundhouse loco. Wgen I bashed it, never thought of DCC, My bad. Finally got a Power Cab. Retired it. It ran very well.
Rich
If you ever fall over in public, pick yourself up and say “sorry it’s been a while since I inhabited a body.” And just walk away.
Good lord Miss Agnes! I logged in to see if just MAYBE someone might have replied to my newbie electrical query. Thank you all for replying. So much good info here, and even some info about historical house wiring! What a bonanza!I certainly will take to heart all these warnings about not blowing up my old DC engines. I might just get in the habit of physically removing all my DC locos from the layout whenever I want to run my DCC engine (I only have one, just bought it on eBay. It's a beauty and I don't want to ruin it: Atlas yellow-box RS-3 custom-painted n the rare, original SP&S "as delivered" livery of dark green and oxide red.)Randy, yes, THAT is the switch. I love it. It looks like a mad scientist switch, a Dr. Frankenstein switch. Thanks for finding that.And Kevin, I love that your layout is in "a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954." That's the same world I'm modeling. What are the odds?Thanks all for the warm welcome and great info and ideas! I think next I'm going to get a drawing of my layout plan and post it in here and let you guys gnaw on it. I'm sure it can be improved by the hive mind.-Matt
DPDT center off works. Make sure you throw the switch to the appropriate system BEFORE you power the system up. This minimizes the chance of a power spike that will fry your DCC system. Don't ask me how I know this.....
Bill
"Never try to teach a pig to sing. It wastes your time and annoys the pig"
What he needs is a switch like STSHK11-3P. This is an enclosed three-pole double-throw center-off switch; he can wire the hot side of the power to the throttle equipment to the third pole to guarantee the power switches along with the track. (Or use relays or a switched outlet...)
rrinker Which switch? THis one! https://www.amazon.com/AXLIZER-Electricity-Experimental-Simultaneous-Connections/dp/B08RHZF4FM/ref=sr_1_16?dchild=1&keywords=knife+switch&qid=1614195592&sr=8-16 It is physically impossible to get DC and DCC togehter if this is the switch used to isolate the two,. The layout is either goign to be all DC, or all DCC. Plus it looks cool. --Randy
And you get to re-live a (small) bit of Hollywood history from the movie "Young Frankenstein." Or is it "Fran - ken - steeeeen"?
RHB
ROBERT BRABANDOr is it "Fran - ken - steeeeen"?
Well, then, my name is pronounced eyegore.
ROBERT BRABANDAnd you get to re-live a (small) bit of Hollywood history from the movie "Young Frankenstein." Or is it "Fran - ken - steeeeen"?
They make light-switch covers that give you a better James Whale flavor, although not with the "improved" version of the idea I used in college, which played the sound of huge contacts smashing closed or open and the crackle of electricity when the fake switch was thrown. You could do that with a greeting-card-size sound chip today...
Walk this way!
If you hit up some antique markets you probably will eventually find a really big version of the knife switch, not that relatively puny plastic one they sell today.
We use two plugs and one outlet on our club layout. One plug connected to DCC power the other connected to DC power. We just plug the one we want to run with into the outlet that is connected to the track bus. Simple and it keeps us from inadvertantly knocking a switch to the worng position. Anderson Powerpoles are our choice of connectors.
Martin Myers
Some perhaps useful observations from the ham community on Anderson Powerpole connectors in the model-railroading size range:
https://m.youtube.com/watch?v=o31iuOcQ-jo
We've been using PowerPole connectors on the club modular layout for at least 10 years now. That's many cycles of connection and disconnection, and as far as I am aware of, none have ever needed repalcement. Since I need to have a moveable section to get past my furance and water heater, I intend on using them to disconnect the power bus when moving the section. It's not like a duckunder liftout where it needs to be constantly accessed, so no sense in making some complex automatic contact system.
If you're not going to use the mad scientist knife switch, then I'd definitely go with the plug method which is also about as foolproof as it gets - can't plug 2 things into the same socket, so only the DC or the DCC system could ever be plugged in at any given time.
crossthedogGood lord Miss Agnes! I logged in to see if just MAYBE someone might have replied to my newbie electrical query. Thank you all for replying. So much good info here, and even some info about historical house wiring! What a bonanza!
Glad you found your thread. I was concerned that when it was moved to the DCC/Electronics section we might lose you forever.
crossthedogAnd Kevin, I love that your layout is in "a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954." That's the same world I'm modeling. What are the odds?
If you feel like it, pop on over to the General Discussion section and tell us about your layout and/or your modelling ambitions.
Glad you are here.
Thanks for the further ideas about plugs, guys. That might be the way I go, much as I'd like to throw that big crackly switch and laugh maniacally. But now another worry arises. I'm seeing videos and articles that say that the way I wire my layout depends on whether I'm running DC or DCC. Yet this very thread is about just using one wiring scheme on the layout and simply throwing a switch between power sources. Is this one of those things where absolute best practices would dictate differnet DCC wiring, but reg'lar ol' DC wiring will be fine? Or is there some real imperative to wire according to power source? I'm confused now. Opinions and small rants welcome.
Thanks again, in advance.
It can potentially get complicated if you want multiple cabs ont he DC side so you can run multiple trains, because thent he DCC has to feed into the cab control wiring, and any scheme that simply makes the DCC an extra cab means that in one block you can have it set to DCC and in the next block set to one of the DC cabs and poof goes the magic smoke if you run past the joiners.
If you just want to switch power off in sidings so you can park locos while running a different one in DC, you can put your DC/DCC transfer switch in front of that with no problem. Being able to isolate sections of the layout by cutting power can be helpful in DCC troubleshooting as well.
For me, best practices wiring in DC is two wires to every rail - no common rail. Which also happens to be best practices with DCC wiring. Atlas track plans and some people feel common rail is better or sufficient for DC, but I never wired a DC layout like that, I always gapped both rails and ran 2 wires to each block. So doing DCC is not really different.