Basic wiring questions (Atlas switch machines)

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I apologize in advance, but I'm pretty ignorant on wiring. I've already fried one switch solenoid and would like to avoid messing up anything else.

I'd like to wire up some switch status indicators, and I've been searching, but every circuit out there either requires two separate switches or runs on DC power. Currently, I've got my Atlas switches wired to ~16V AC with each being activated by a SPDT momentary toggle. As you'd expect, they work fine.

Since most of the nifty logic-controlled momentary-switch activated indicator circuits run off 12V DC, can Atlas switches run off 12V DC power or will this fry them? I tried running the Atlas switches off 12V DC, and they appeared to work - weakly.

If anybody's got a way to run two lights off of the 16V AC momentary setup, I'd love to hear how it's wired.

Thanks for any help... :)

NH Mike

CEO & Wheel Cleaner
Atlas switch machines will run off AC or DC since all they are is a coil of wire at each end of the plunger to attract it by magnetism when the coil is powered. A coil of wire is not polarity dependent and does not care whether it is fed AC or DC as long as the current does not exceed what the coil can handle. They will activate quicker on AC simple because the AC terminals provide 16V where the fixed DC only provides 12V. Basic electricity - more voltage applied to the same coil produces a stronger magnetic field.

I have always used Atlas & Peco switch machines wired through a capacitor discharge circuit which gives a good jolt of AC to the coils and don't run contacts for signals or other auxiliaries off them.
AC can easily be turned into DC with a diode and a cap. Then you can use any of the indicator circuits.
Post a link to the indicator circuit you are thinking of using so we can see if there is a way to interface the circuit to an AC powered Atlas switch solenoid.

Mark R.

Custom Painter
You could always use the Atlas Snap Relay ....

Just wire it in parallel with the switch machine you now have and it will basically give you a DPDT switch that you could connect lights to using whatever power source you want.

Thanks for your replies, guys. It's good to know that the switches will run off DC. Rather than bore you guys with loads of basic questions, what's the best inexpensive reference for this kind of basic model railroad wiring?

I like Mark's idea of using the Atlas snap relay, but I assume I could just buy a few components from Radio Shack (cheaper) - if only I knew what I was doing.

Waltr, this is a circuit I found online that looks like it does what I want. Needlessly complicated for what I'm after? I'd rather not have to buy IC chips/etc just to switch a few LED's:

I got this from something called "The Armadillo & Western Railroad" website (I'm sure this is probably well-know to everyone here).
Ok. So lets go over the circuit a little so you can understand how it works.
The SW should be a momentary SPDT (center off). When the SW is thrown to one side it energizes one of the coils to trow the turn-out. The SW is then released and the coil de-energizes.
The CD4011, CMOS NAND gates, and wired as a flip-flop (google this). A flip-flop will hold its two outputs (pins 3 & 4) at the level momentary presented to an input (pins 1 or 6). In essences the flip-flop 'latches' a momentary high voltage level (digital logic levels) so the corresponding LED stay lit after the SW is released.
Due to the coil being only momentarily energized a latching circuit is required to 'remember' which direction the turn-out coil was energized in.

Now for the DC power. Since you have 16VAC a 'full wave bridge' rectifier and a filter cap is all that is needed to power the circuit you posted. The CD4011 is rated for up to 15VDC so you will need to measure the output voltage from the rectifier to ensure it does not exceed the CD4011's max rating.

Here are some links to other circuit ideas which use a capacitor discharge.

Theory and a schematic of a 16VAC to DC circuit:
If I may, I'd like to confirm my understanding of the "full wave bridge rectifier" section of the circuit. Based on the schematics in the links (thank you), can you confirm that the following portion will provide a DC power output from my AC input?

Full capacitor-charged circuit:

Portion that I hope will get me DC power:

I plan on tackling this in stages, since I'm feeling pretty stupid right now and don't want to keep frying stuff. If the circuit portion in question gets me my DC power source, then I'll add the charge cap portion and the following circuit to add my indicators. I plan on using my existing SPDT momentary switches in place of DPDT's:

Does this make sense, or will I just create junk?
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Yes, you have the correct circuit isolated to get you DC power (second schematic in above post.
The last schematic should work (I've never tried it) and also sounds like the circuit Mike uses (see post #2). The way this one works is:
With the switch (S1) is the position shown, The cap C1 charges through resistor R1. Once it is charged C1 (+) is at the same voltage as the input voltage and no current is flowing through R1.
When the switch is thrown, S1a down & S1b up, the energy stored in C1 discharges into coil A. The cap has stored a fairly high amount of energy which will energize coil A causing the turn-out to switch. Once the cap is 'discharged' there will be some current flowing through R1 (by Ohm's Law the current = E/R = 16V/1000 Ohms = 16mA). This really isn't enough current to over heat the coil. In the mean time, being the the switch is now in the other position, C2 charges through R2 to get ready to engerize coil B when the switch (S1) gets thrown again.

Notes on building electronics:
If you don't have one buy an inexpensive DMM (Digital multi meter).
Measure voltages and connections (Ohm scale) before connecting to anything expensive.
Expect to goof up and cause some thing to smoke, then figure out why it smoked so you don't do it again.

good luck and have fun.
Thanks! I admit that I already had a cheap needle-type multimeter from Radio shack (~$20). Now that I'm an electronics "genius" (heavy sarcasm there), I had to get a nicer digital-display meter (~$50) last week. Frankly, I was having difficulty making sense of what the needle was telling me - too many different scales. Gotta have good tools, right? :D

I'll update the thread once I've given these circuits a try.
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NH Mike

CEO & Wheel Cleaner
One other point relative to Atlas machines I found is non electrical. If a switch machine seems sluggish or relatively slow check and be sure there isn't any ballast or ballast cement under or around the throw bar. Even being extra careful with ballast it is still possible for your ballast glue to creep under the bar. And over a long period of time the plunger or slide arm can collect a coating of grime and dust crud. In that case I remove the switch machine and spray a shot of electrical contact cleaner through the slot where the little manual operating pin sticks up while working it back and forth. As a quick test gently shake the switch machine back and forth and if the plunger moves freely and easily the unit is clean and ready to go back on the turnout.

Waltr, you're correct on what my cap-disch circuit is. I bought it many years ago as a ready to use unit from a local hobby shop. The name of the outfit that made it is long forgotten. Besides working excellently all these years it also has a red LED on the circuit board to indicate when the cap is fully recharged. Neat to look at but probably unecessary as it takes maybe 2 seconds to recharge. I've found it more useful as a reminder I didn't shut off the power supply. LOL is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to