Separate Power for Turnouts

[jmarley76]

Here is my situation: Running a 36x72 layout (N scale) using a Digitrax Zephyr. I am using Unitrack turnouts (snap switches?). I recently added a 46x72 L shaped extension using Atlas turnouts and found the Zephyr did not put out enough power to operate the additional switch controls. At that point, I broke out my old MRC Tech II 1400 and hooked up the switches to it. It works great, and I now have seperate power for track and switches.

Here is my problem: I would like to use the MRC pack for something else. Is there a power source, plug in, or transformer I can use to replace the pack?

[jdcolombo]

I'm not sure if Atlas switch machines require AC or DC power, but either way you should be able to find a 1-amp 12v wall-wart for under $10.  Cut off the plug and wire it up.  If you need an on-off switch, use a cheap outlet strip with an on/off.  Or buy a cheap used power pack to do the same thing.

John C.

[jmarley76]

I was hoping it would be fairly simple. Thanks, John! 

[peteski]

If these are the twin-coil machines you might want to pick up not 12 but 15V power supply. The "accessories" output on most throttles is 16V AC, so 12V might not be high enough to throw the switch (especially if thy are long distance away from the supply).  Or better yet, build yourself a capacitive-discharge power supply. Those have plenty of power but won't burn out the switch-machine coils of you hold the button in for too long.

[jmarley76]

The MRC Tech II 1400 I'm using puts out 18 VAC, total output 13 VA. So maybe even get an 18V?

[jdcolombo]

Peteski is correct - you probably do need more than 12v, and 16v AC is more common than either 15v or 18v.  Here's a 16v AC 20VA wall transformer for $7:

http://www.allelectronics.com/make-a-store/item/actx-1620/16-vac-20-va-wall-transformer/1.html

A capacitive discharge unit is very useful for twin-coil switch machines.  Here's a page with more info and a circuit you can build for under $20:

http://www.awrr.com/cdsupply.html

John C.

[jmarley76]

Thanks for the link! I can definitely wire up the transformer. Building a circuit is another thing... 

[jmarley76]

Wanted to give an update on this, although it's feels like an eon ago...

I ended up ordering a 24VAC 20VA transformer. I plugged it into a power strip so I can turn it off when not in use. I finished wiring it up and it works perfectly.

So know I can build something else to use MRC Railpower 1400 since the wall transformer freed it up.

[peteski]

Good to know Jeff - nice of you to follow up.
But make sure to always press the pushbutton for a very short time - I suspect that with 24V feeding it, the coil in the switch machine will heat up and possibly burn out rather fast.

[jmarley76]

I thought a long while on the 16VAC vs. 24VAC. Since they were being fed 18VAC from the Railpower 1400, I decide to go a little more instead of less.

I was visiting Ron Hickey's layout and someone leaned on the control panel for a few minutes until the corresponding switch started smoking. It even had a flame shoot out of it for a few seconds. It was unfortunate that it happened, but a good lesson none the less.

[peteski]

I was visiting Ron Hickey's layout and someone leaned on the control panel for a few minutes until the corresponding switch started smoking. It even had a flame shoot out of it for a few seconds. It was unfortunate that it happened, but a good lesson none the less.

Capacities discharge power supply totally eliminates this problem.  And it is a very simple circuit with just few components.