I'll be in the process of planning my first real layout for quite some time, and in the meantime I've been setting up smaller layouts to test different aspects and scenarios. When I start my larger layout, I plan to use DC to power tortoise switched on Ross switches. Knowing that will be the case, I'm planning to use some LEDs elsewhere on the layout that will utilize the DC power and keep less of a load on my train transformers. With that in mind, I see some great uses for LEDs in a control panel. I want to experiment with indicator lights on the control panel to indicate when sidings are powered or not.

My question is this: Can I use a DPST switch and utilize one pole for track power (AC) and use the other pole to control the LED? The switches are rated for different loads DC and AC,  but I haven't seen anything about whether it's safe to have both on the switch at the same time (of course not on the same pole). My understanding is that both poles should be isolated completely, but I'm hoping someone can shed some light for me as to whether this is safe or if there's a better way handle this that doesn't involve my track power and rectifiers.

Original Post

Yes, you can do this but it might be better to isolate the AC away from the DC with a relay. Because the connections to the switch are in such close proximity to one another, there is some danger of causing a short in one or both of the circuits (just my opinion). With great care and proper heat shrink, you could diminish the associated dangers. But I'd use a relay.

I have many places on my layout where I use DPDT mini toggle switches to control track power.  These switches have 18 volts AC on one set of poles for track power and 12 volts DC on the other set of poles for LED indicators (with resistors) to show when power is "on" to that track.  You do need to solder the wires carefully to the toggles.

 

As others have stated, "yes" to your original question.

But elaborating a bit on Leo's suggestion:

IMG_4670

Since you have the 12V DC control voltage already, you can choose from a variety of handsome (IMO) automotive LED switches.  These SPST function with a standard 3-terminal connection and built-in LED/resistor.  Less than $1 on eBay shipped.  These switch 12V DC.

The 12V relay modules come 1,2,4,8, etc. relays (10 Amp contacts) per module for about $1 per relay on eBay shipped.

One advantage is the control wires from your panel to the relay module(s) carries only low-current 12V DC...rather than the hi-current AC track voltage.  This means thinner gauge wiring which can be easier to work with, less bulky, less expensive, typically available in convenient ribbon/multi-conductor cables, and so on.  Sometimes sketching out a "to-scale" layout diagram with wiring (e.g., using color coded or thick/thin lines for thick vs. thin wires) can be quite revealing.

In general, using low-voltage DC control signals typically provides more flexibility if/when you add additional control points - such as a 2nd control panel.  In other words, much easier to work with low-current, low-voltage DC than hi-current AC.

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I agree with Bob, and also I think you guys are way overthinking/over-complicating this. A DPDT switch with AC on one set of contacts and DC on the other set will work just fine.

The only caveat is that these miniature switches seem to last for fewer cycles than full size switches. It problem seems to be mechanical with the lever itself.

Just my experience.

RoyBoy

RoyBoy posted:

I agree with Bob, and also I think you guys are way overthinking/over-complicating this. A DPDT switch with AC on one set of contacts and DC on the other set will work just fine.

The only caveat is that these miniature switches seem to last for fewer cycles than full size switches. It problem seems to be mechanical with the lever itself.

Just my experience.

I'm having a hard time with this simple solution. How do you wire two different voltage sources to a dpdt switch so you can power up a section of track (ac) and power up a diode (dc) at the same time. A diagram would be great.

Steve

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