Using a DPDT switch like that (you want the center off type, so there is a middle position when NEITHER system is connected - this prevents a break before make situation connecting DC to DCC as you move the toggle lever) is the way to do it. You could go all steampunk and find a DPDT knife switch.
Contact rating on the toggle is how much it can handle while switching. That's much less than it can pass while closed. In most cases you wouldn;t be throwing the switch with much if any load on it - you're not going to get a bunch of trains moving then switch suddenly from DC to DCC or vice-versa, and even so, 10 amps is a LOT of trains. 5 or 6 HO locos with sound don't draw 10 amps. They don't even draw 5 amps. Plus those ratings are usually at 250 VAC. As important as the current limit is the physical size of the switch. There are plenty of tiny switches that claim to be rated ar 3 or 5 amps at 250 VAC but you'll never be able to attach wires capable of those levels to them. Plus the handles are tiny. Look for something big enough to easily attach relatively heavy wires to (short pieces of #18, when the rest of the bus is #14, isn;t a problem) with a big enough lever to easily switch back and forth. Most likely such a large toggle will be rated at least 5 amps, if not 10.
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
Thanks for your caveats gentlemen. I understand the many, many dangers of mixing DC and DCC, including all of the disasters you point out.
As I understand it though is that using a DPDT center off toggle switch, with DC power going into one side, DCC power going into the other, and the track bus coming out of the center poles there is no way the two power sources can mix, not possible that both sources of power can make their way into the track bus simultaneously.
I can see how some people could convince themselves to have a section of the layout powered w/ DC and other sections powered by DCC, and they are smart enough to never throw a turnout to allow a locomotive to cross from one to the other. I subscribe to the same philosophy you do - if it can be done, sooner or later you will do it, and then there's a price to be paid.
I suppose a failure of the DPDT toggle might make my plan dangerous, but I would use something rated for at least 10 amps (more than either source could pump out, right?).
If push comes to shove I could be convinced to do a physical disconnect of the power source I'm not using for that operating session, but I do have confidence the toggle switch, which can only let one power source through to the bus at a time, will do the trick.
I will be the first to admit though that over and over again I have proven the fact that a college education doesn't make you smart, so . . . . .
Again, thanks for the warnings. I'll do some soul-searching on this.
Robert
And even if you don;t mess up and cross the boundaries, if the frogs are connected tot he Frog Juicer which is connected to DCC, and a train running on DC goes over a different route, you now are making a DC to DCC connection via the Frog Juicer. When Duncan says using them on DC won;t hurt them, I don't think he means when the Juicer becomes the bridge between DC and DCC, rather if you install Frog Juicers but also have the ability to switch your entire layout between DC or DCC, the Juicers will not be harmed in DC mode, but neither will they power the frogs.
All DC or all DCC, that's the way to wire the layout if you have certain DC engines that are not practical to convert (though there's really hardly anything you can't convert). Mixing the two at the same time is only asking for trouble. You may have no problems 999 times, but that 1000th time, when a visitor you are showing the layotu off to asks a question, and you miss flipping a critical turnout - poof! It can and will blow the DCC system, not just melt a cheap decoder or a wire in a loco.
ROBERT BRABAND...the crossover is in an industrial area and I could still run DC trains on the mains....
I am concerned about this statement. It indicates that you may be running DC and DCC on the same layout at the same time. Please don't do that. We don't want to do a post mortem on your power pack or DCC base station, and that's a risk if DC and DCC circuits get crossed, perhaps by error or perhaps by a short after a derailment. "Never the twain shall meet" is particularly apt here.
It takes an iron man to play with a toy iron horse.
Thank you sir. I had gone looking on the Tam Valley site and couldn't track that info down, so thanks for covering me on that. To the basement!
From the Tam Valley web site:
Will DC damage the frog juicer? No- although they will not power the frogs, they will not be damaged by DC so feel free to run your layout in DC mode with the frog juicers attached.
I have the right to remain silent. By posting here I have given up that right and accept that anything I say can and will be used as evidence to critique me.
I'm working on my n-scale layout, intend to use DCC with the option of DC, both routed through the appropriate DPDT toggle so only one power source can go to the track bus at any one time.
But, I need to use a Dual Frog Juicer to power frogs on a Peco Electrofrog crossing. All frogs on the Peco Electrofrog turnouts are powered through Tortoise units, and I think they are okay with the DC. But the Frog Juicer says to use it only with DCC.
If I use the Juicer and DC, what are the consequences? Is it just that the DC power won't get to the frogs (the crossover is in an industrial area and I could still run DC trains on the mains). Or will the Frog Juicer get fried? Or the transformer?