How many amps?

I agree with Dale about the CD system, Atlas switch coils will go up in smoke in just a few seconds if you don't remove the power!

I just tried one and got anywhere from .3 to .5 amps. Seems to depend on how long the button is pressed, shorter (very quick press) was .3 and longer (probably a more normal press) was .5. I still mean just a quick press here (short and long) so as not to burn up the switch motor. I would probably use the .5 amp to be safe.

And as Dale H suggested, I measured about 30 ohms on each coil to com, using your 15 volts / 30 ohms = .5 amps. Really close to what I was reading with the slightly longer button press. So you should be in the ball park with the .5 amps and your 20 switch machines total would be 10 amps. I would think you could get by with at least half that if not even less. As you say, it's unlikely that they will be operated all at the same time.

Maybe Dale H or GRJ will be back to add more to the sizing of the transformer as I am not really sure how to calculate how many switches should be allowed for at one time other than guessing? To me, the 10 amps seems like an awful lot just for some switches?

Also as Dale H and GRJ said the cap discharge idea is a good one for the Atlas switch motors. I may do that on some of mine that I don't use the 6924 non-derail boards on.

The CD discharge circuit will also take much less peak to charge the capacitors, and thus evens out the load a bit more.  Truthfully, if the transformer isn't driving any incandescent lights, a 2-3A transformer would be plenty for 20 switches in typical use.

There was a discussion about a CD system where there was one power supply for all the switch machines, I don't recall the title now.  I don't see why you'd need the power for each switch machine.  I'd probably just diode isolate each capacitor from the charging circuit so it couldn't discharge through the charging circuit and parallel all of the capacitor/diode combos to one healthy power supply to charge any discharged capacitor.  When a switch operation discharges the cap, it would be quickly charged by the common power supply.

You could make the whole affair a single assembly with all the caps/diodes and the power supply if you like.

GRJ, by common power supply do you mean the bridge rectifier in Dale's diagram?

If so I agree that you shouldn't need 20 bridge rectifiers in a CD system...but how about the 20 x 2 = 40 capacitors for the 20 switches?  The suggested 2200uF 50V capacitors run about 50 cents each on eBay from Asia, about $1 each from DigiKey, and a whopping $4+ each from Radio Shack.  That can add up to quite a bit of coin just for capacitors!  I don't know if George has his activation switches already wired up, but if he also has to replace 20 existing activation switches with "new" DPDT switches as used in the suggested CD system...

Again, just asking from an Electrical Forum perspective since I'm not familiar with the Atlas switch machines and CD systems.

Stan2004 and GRJ, very interesting idea about combining the items for the switches. Please continue the discussion with all the details you can add. (and don't type too fast)

Well Stan, $20 for capacitors or $10/ea every time you smoke an Atlas switch machine, which do you choose.   It will obviously cost something to do the CD system, but most folks find that it's worth it for these switch types.

Dale, it that doesn't scare the crap out of him, nothing will!

It doesn't.

Such wiring layouts are a journey, arrived at in step-by-step fashion.  And when it comes to wiring I am sort of OCD about neatness.  So, no, I'm not scared by it.

However, I do have more new information at this point.  These questions regarding the Atlas switches are for my friend's layout, which I mostly designed and am helping him build.  I found out that he has no buttons planned for throwing the switches - it will all be done with the CAB-1 remote under TMCC.  Last night we hooked up a temporary 15 VAC transformer and tested an Atlas machine with it.  Worked great.  I don't know what the TMCC command uses in terms of amp draw for the throw, but I'm guessing that may no longer be an issue.

Will that information allow us to use a lower voltage for the switch buss?  Perhaps 12VAC?

We will be using TMCC Routes, so perhaps as many as 4 switches will be thrown at once.

So keeping the above in mind, are there any other things I should be aware of in wiring these switches? 

I am very grateful for all the information and guidance you, Dale H, Stan2004, and rtr12 have provided.

George

In the Atlas switch directions, they recommend 16-18 VAC to operate the switch machines. It says AC, but others here have reported using DC with them and getting better performance. I haven't tried any with DC yet and I can't remember what DC voltage others have reported using? 

My layout is still in the 'almost ready to build' state and I have only operated the switches on the bench. I had a couple of temp layouts, but never installed any switches on them. Bench work may arrive next week and then the layout assembly begins!

Edit: Dale H replied while I was typing, he makes a very good point, it is the length of time the button is pressed that burns up the switch machines, not so much the voltage used. They should not burn out unless the TMCC switching device sticks in the on position, regardless of voltage used (within their recommended limits that is).

Dale, pushing the button on the TMCC CAB-1 remote generates (I would think) a discrete command of finite, uniform, and controlled duration.  I don't think you can hold down a button on the remote and get anything but a single measured shot.  I haven't tried this and don't intend to (kids, don't try this at home.  )

In any case, I think we are good here.  At some point, the thought of only using the CAB-1 remote to throw switches might get revisited (I use both button pushes and the CAB-1 remote to throw switches on my PRR Panhandle), but my friend's layout is a twice around and he will have more time / space than I do.

Thanks again.

George

You are correct, 16-18 VAC is the recommended voltage in the directions.  Last night, 15 VAC worked fine.

Interesting point on sticking.  If it did stick, wouldn't you get repeated discrete bursts of current or would it be continuous so as to burn out the switch machine?

George

If you're using something like the SC2 to generate the switch commands, they'll time the switch throws for you, job done.

If they stuck you would constantly get whatever is being sent through them. The only reason I said that is a while back someone reported burning up some of the Atlas switch motors with (I think) an MTH AIU. I know you aren't using the AIU, but it was a similar problem. I don't know the wiring, setup or circumstances of the burnt ones, but I was thinking the AIU also had a momentary setting for switches as does the TMCC device. It was just more a word of caution or FYI, if your TMCC devices don't malfunction you will be fine. There is no way we can prevent the occasional malfunction of electrical or mechanical devices, that's just part of the fun of it all.

Yes, the SC-2 is the device commanding the switch machine.

Thanks!

George