RIght, which is why you can use thin wire for Tortoises. At 15ma, you can run #28 (phone or network wire) to a Torotise 50 feet away (100 feet total of wire for the complete circuit) and get a 0.1 volt drop - 11.9 volts of the initial 12 volts would be delivered to the Tortoise. Negligible. That same wire supporting the .5 amp load of a typical HO locomotive would lose over 3 volts!
--Randy
Modeling the Reading Railroad in the 1950's
Visit my web site at www.readingeastpenn.com for construction updates, DCC Info, and more.
There's a calculator at the bottom of this page:
http://www.powerstream.com/Wire_Size.htm
The problem rarely is current. (Tortoises use very little) The problem is with thinner gauge wire, you get much quicker voltage drops over the run when you crank the current. For example, if I was running 12V DC over 10 feet with Aluminum 28 gauge wire, I would get over a 7.7 volt drop with 3 amps, leaving me only 4.3V to work with. With 1 amp over the same run you only get a 2.6V drop or 9.4V at the end.
Don - Specializing in layout DC->DCC conversions
Modeling C&O transition era and steel industries There's Nothing Like Big Steam!
Thanks, Randy and MisterBeasley, for your complete and helpful replies. I'm all set.
I discovered that Circuitron has the Snapper CD unit and toggles for both Peco and, of course, tortoise switch machines. As I don't understand electronics, I'll probably opt for the ready-made solution.
Now, 22 AWG solid wire in light and dark colors other than red and black (which I'm using for feeders)-- that's another story!
Rick Krall
Rob Paisley's circuit is good, or if you can dig up a copy of the old "Practical Electornic Projects for Model Railroaders" by Peter J Thorne that Kalmbach published years ago, there's one in there. Same circuit, basically, but some explanations for it. CD power supplies are pretty simple and outside of getting the capacitor polarity correct, are pretty simple for a beginenr to build. And it's kind of hard to get the capacitor polarity wrong since there is a strip of "-" signs down the side next to the negative terminal.
For Tortoises, they want plain DC. No momentary contacts, they are designed to have power applied all the time. You can use 9-12 volts DC, connected to the Tortoise via a DPDT toggle wired like a reversing switch - the four corner terminals connected like an X, power supply feeds to the terminals on one end, Tortoise connected to two middle terminals. A Tortoise draws very little power, about 15ma. 100 would draw 1.5 amps. So all you need is a small wall-plug transformer.
I built my own CD circuit. I power it from an old train transformer. Here's a starting point:
http://home.cogeco.ca/~rpaisley4/CDPSU.html
This is a simple circuit with very few components, so I thought it was a good starting point for learning to build this kind of thing. It had been a long time since I did any soldering, too, so it got me started.
For twin-coils like Peco or Atlas, you want a single-pole, double-throw (SPDT) momentary contact toggle. These will spring back to the center after you throw them. I don't have any Tortoises, so hopefully someone else will chime in with the right answer.
It takes an iron man to play with a toy iron horse.
rrinker For solenoid switch motors I'd use something a bit heavier than phoen wire, as they draw a fair amount of current, although only for a very short time.
For solenoid switch motors I'd use something a bit heavier than phoen wire, as they draw a fair amount of current, although only for a very short time.
Thanks; I use a short length of 22 AWG to solder feeders to the track (HO), so I'll use that.
(Incidentally, I couldn't find the answer to my "wire gauge for accessories" question anywhere in the MR forums. I hope it's the marginal search function rather than a mental deficiency on my part!)
MisterBeasleyAre you powering these from locally-mounted (i.e., fascia) toggle switches? I'm curious about how else your drops would be so short.
Are you powering these from locally-mounted (i.e., fascia) toggle switches? I'm curious about how else your drops would be so short.
I think my Beginner is showing through. I assumed a drop to a bus and wasn't thinking about the toggle. The run to the fascia will be slightly under 6 feet. Looking at the Peco wiring diagram following your response, I now understand (I think) that the power goes through the CD unit to the toggle and thence to the switch machine.
Could you please advise a source for a CD unit and what kind of toggle switch I should use for the Peco and the Tortoise? I believe they'd be different b/c the switch machines operate differently.
Thanks for your response.
Tortoises draw such little current that phone wire is perfectly fine for them. At the low current draw of a Tortoise, even a 30 or 40 foot run of thin phone wire won;t have much of a voltage drop - plus if you're starting with 12 volts, dropping a few won't hurt, Tortoises work fine even down to 5-6 volts. 8 conductor network cable is great if you aren't using the Tortoise contacts for track power - since there's 8 terminals on the Tortoise.
I use 4-conductor telephone cable for my Atlas and Peco switch machines. Even though I only need 3 wires, the 4-conductor cable is cheaper than anything else. Most of my lines are 8-10 feet, and I have no trouble with them. The phone cable is really skinny stuff, like 24 or 26 AWG.
I've found that Peco switch machines really, really like a capacitive discharge circuit. To flip the points with that little spring in the turnout, they need a lot more "kick" than an Atlas. A CD circuit also protects the switch machine in the event that your toggle switch hangs up and you get constant voltage to the twin-coil machine. Without a CD circuit, I've fried Atlas machines for this reason. It was obvious from the smell that something was very, very wrong. When I had a toggle hang up with my CD circuit, I had a heck of a time figuring out what was wrong, but my switch machine survived with no damage.
I'm about to install Peco and Tortoise turnout motors (switch machines).
What gauge wire should I use for the drop? The drop should be no more than 12 inches.
Thanks.