Hmm...

Don't see anything amiss...

Looks pretty straight forward.

Thanks, Alan

I know, but this one has had me mildly stumped for a few days.  I've been trying to work it out in my head (while doing other things, so not giving it my full attention) and I keep having the vague feeling that I'm missing something.  That's why I asked for a second opinion.

I'm off to Radio Shack to get some switches!

Looks good to go to me

I would need to make sure every thing is clearly labeled.  But that is me.  I need a test track of some kind so I may steal some of this...

Be my guest

Help yourself, Ken.  My plan is to mount drawer slides on the whole thing and attach it to the bottom of my layout.  that way I can pull it out whenever I need to use the programing track, or just leave it pushed in with a UT-4 plugged in for normal operation.

Another benefit I see of doing it this way is that it allows me to isolate the layout while still having DCC track power on the test track.  Since the Zephyr can turn the main line outputs into full power programing outputs, it will be handy to be able to put an engine on the test track, program it in blast mode, and not have to worry about programing everything else on the layout.

I know what you are missing

Radio Shack does  not have switches anymore.  Go to someplace like Skycraft in Orlando instead.  Not only do they have switches, but they are cheaper than RS used to have.  (I was just there yesterday, picking up some SPST switches for a project I have, after not being able to get them at RS.)

Looks smoke-proof, Ken

I don't see any issues, and I read prints as part of my job.

I prefer buying local

That's one heck of a drive for me, James.  I just got back from a trip into town (including Radio Shack), and I have what I need, though not exactly what I'd hoped to get.  RS had no more than 2 of any specific DPDT center-off switch, so I have one with a different toggle on it.  I'm not sure yet just what I'll use the odd-ball for, but it's functionally the same, so just an aesthetic issue.

I miss the days when I could go into Radio Shack and buy whatever components I needed.  These days they're only interested (well, not interested as much as grudgingly willing to put down their phones) in selling fancy electronics and cell phones.  Looks like I'm going to be forced to start ordering components on line in the future.

The Radio Shack website shows switches, some in-store

http://www.radioshack.com/family/index.jsp?categoryId=2032278

couple comments

The should work fine.  Just make sure the switches completely break contact before making contact with the other contact. Double throw switches normally do, but I would make sure.

When I made something like this for our club, I made it so you had to unplug the DCC before you can plug in the D.C.  and vice versa.  I did not want someone to accidentally throw the switch and send D.C. to a decoder or vice versa.

Safety first?

That's part of the reason I made sure to get center-off switches.  I figure that should guarantee that I don't cross the connection.

This is probably 99% for my own use, so I figure I can afford to make things a little easier and take the risk.  Besides, a decoder is supposed to be fine on DC, from what I understand.

DCC/DC

I believe that as Ken says, today's decoders can tolerate DC. What you absolutely want to avoid is DC power to the track while DCC is still connected. It is the DCC command station that will be damaged. (Don't ask me how I know!)

With the Zephyr Extra I can do programming on the main if you don't care about reading back the settings. Blast programming isn't always necessary, depending on the decoder. If you blast, remove all your other locos or they will all be programmed simultaneously. If you don't blast, simply address your specific loco 1st, then proceed to program it. I can do that with a BLI with a QSI sound decoder that talks back to me with its settings when programming on the main.

Dante

My test track

I built a similar unit but with a much longer test track and it is not mounted on the drawer for the electronics. However I used a 4 pole 6 position Oak Brand rotary switch that I purchased at a used electronics parts store.

I set it up like this:-

Position 1 Off

Position 2 DCC to layout

Position 3 DCC to Programming/Test Track

Position 4 Off

Position 5 DC to Layout

Position 6 DC to Programming/Test Track

This kept the DCC and DC on separate parts of the rotary switch. I was deathly afraid of getting DC connected to the DCC Master unit as a friend did this and fried it!!

I put the off position between the DC/DCC positions just in case the ortary momentarily shorted between position even thought the switch is a no-shorting version! Guess I am a belts and braces man. LOL.

OKGraeme

Take Care

Your diagram looks like the underside view so that when you want to select DC for the main track the toggle on top of the switch will have to be thrown toward the DCC wired side when looking at the bottom.

Wire one and check - I think you will find the inputs have to be on the opposite ends of the switches to what you have shown.

all the best...Rod

@ Gramme, Rod

If you have the extra positions, you might as well use them!  One of the reasons I prefer the toggles is that it will allow me to put DC on the test track while still running the layout on DCC.  In practice, I'm not sure that will ever be an issue, but I like having the ability.

I plan on putting all of the switches in a line, with the toggles flipping left or right toward the respective inputs.  The diagram is just the most convenient way I could come up with of drawing the wiring, and does not represent the actual physical arrangement.

Program Track Connections

The only thing I don't see is a PR3 or other computer interface for use with JMRI DecoderPro and other programming software.  I've built almost the identical circuitry for my 2 ft. programming track to toggle between DCC Prog/Main, and DC.  It works well, but as has been stated, must be well labeled to avoid frustration when wondering why your locomotive isn't accepting your inputs.  Usually a toggle is set wrong.  Also, if you use an older Zephyr (as mine is) you may need a power booster of some sort for programming sound decoders.  Hope this works for you as well as it has for me.

DPDT Center off

Ken, You really don't need DPDT Center Off switches, 'A' position or 'B" position are either on or off, but if the center Off position makes you feel more secure, fine.

I would personally add three more switches, DPST ON/OFF and add them to each pair of wires leaving your controllers to ensure that the opposite power source is disconnected from the circuit when operating either DCC Main and Programming or DC. But then that is just me!

Ralph

Not if they are Make-before-break

Dear Ralph,

Using raw A/B DPDT switches is fine, IF the switch is a Guaranteed BREAK-before-Make type.

If it's a MAKE-before-Break, you have a recipe for disaster...

IF however you use a 3PDT (centre-off) switch from the outset,
the problem is inherrently and automatically avoided.

I know I'd rather "Setup for Success" from the outset, than "flirt with failure"...
(and it only takes a single not-100%-sure RadioShack staffer to find you buying and wiring up with M-b4-B switches when you Real Really Do Not Want to...)

Happy Modelling,
Aim to Improve,
Prof Klyzlr

Center Off is good ...

... as it allows you to chose not to power the rails from either source, while ensuring that only one source can be aligned at any given time.  Separate On-Off switches will be forgotten or inadvertently switched at the wrong time and *poof* something bad happens.  Keep it simple ... but make it idiot proof.  

Power switches

I have those already.  There's a switch on the power strip (located where I can easily reach it) which will kill power to the whole thing.  Each throttle then has its own power switch built in.

Also, as Prof said, the center-off switches aren't absolutely needed, but for an extra couple dollars I bought a lot of peace of mind and the ability to completely isolate the track if needed.

Re DCC/DC

ALL decoders are ok on DC, it is part of the specs for DCC if not then they are not NMRA complaint.

Connecting DC and DCC will probably damage the finals of the DC controller but not always and not the DCC (I have run my loco from DCC to DC and back again on more than one occasion without any problems, the first time was by accident but after that just to prove it can be done, but then my layout wiring is all "wrong" according to the "experts"

Ken, your diagram is fine.

Tony