125 VAC Toggle Switch Mystery

Hardcoaler Jun 29, 2018

  1. Hardcoaler

    Hardcoaler TrainBoard Member

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    As I plan the electrical system for my new N road, I want to repeat a feature I've had in all of my previous layouts -- a master ON/OFF switch to assure that everything is cut from household power.

    A nearly 40 year old obsolete Radio Shack toggle switch is shown below that I used long ago. I like it because the toggle action is Rolls Royce smooth and tip glows amber when the power is on. It has three connections and I've long since forgotten how I had it wired. Can someone help? I'd rather not hook it to house current to experiment.

    When I hook an ohmmeter to the bottom connections, it switches on and off, but the top connection has me baffled. Do you think that it's what powers the lamp in the tip? The top connection has no continuity with either of the bottom two regardless of switch position. Thanks for any advice.

    Switch.jpg
     
  2. Jimbo20

    Jimbo20 TrainBoard Member

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    As the switch is labelled as 125V and 250V, my guess is that the indicator lamp is a Neon (gas discharge) and would appear as open circuit with a standard ohmmeter. So the top connection would connect to the other side of your household supply (sorry as I'm in the UK I don't know what you in the US call that?). If you then find that the indicator is permanantly on, you simply reverse the bottom two connections....

    Jim

    Meant to say, the neon lamp will only illuminate if more than about 80V is applied to it....
     
    Last edited: Jun 29, 2018
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  3. Hardcoaler

    Hardcoaler TrainBoard Member

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    Thanks Jim. I'll bet you are correct with the lamp being gas discharge. When I read your post, I unscrewed the clear cap and the unusual lamp within appears to have posts, but no filament between them. Thank you. I think I now know what to try and will do so in safety.
     
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  4. Jimbo20

    Jimbo20 TrainBoard Member

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    Yep, that description sounds like a Neon!

    You should find a resistor is fitted to one side of the lamp, though it may be hidden inside the switch.
     
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  5. Hardcoaler

    Hardcoaler TrainBoard Member

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    I just checked and as you guessed, the resistor must be hidden.

    I must note my smile upon having a Brit respond to my question about a toggle switch with satisfying action I compared to a Rolls Royce. :)
     
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  6. acptulsa

    acptulsa TrainBoard Member

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    Absolutely, Jim. And we usually say 'ground' or 'common'. Provided, of course, you install the switch in the 'hot' leg.

    If the bulb worked off the power being fed to whatever the switch controls, it would affect the voltage the device gets--and the load could cause the bulb to be dim or flicker. Therefore, the switch is sort of a double pole switch. When turned on, it sends current to the device and to the bulb. But the current does not go through the bulb to the device. Now, presumably the device is also connected to the other leg for a complete circuit. But the bulb needs to be connected to the other leg too, or it won't be on a complete circuit, and it won't work.

    It doesn't matter which way current goes through a switch, and unlike LEDs, it doesn't matter which way current goes through most bulbs (which is why I think it's hilarious that, thanks to vaguely-worded federal regulations, a simple lamp with nothing but a socket and a switch must have a polarized plug). But since the feed goes to both outputs, those bottom two terminals are not interchangeable. One is always connected in parallel to the bulb, and the other is only connected when the switch is on.

    Wire one leg of your source to one of the bottom terminals, and tap into the other leg of your source and jumper it to the top terminal. Wire the other bottom leg to your power pack and test. If the bulb comes on all the time, pull the plug (or the fuse, or kill the breaker) again and reverse the wires to the bottom two terminals.
     
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  7. drbnc

    drbnc TrainBoard Member

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    Top lug should be ground, terminal directly below that is +, and the other terminal is whatever you are powering. You need a + and ground for the light.
     

    Attached Files:

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  8. Jimbo20

    Jimbo20 TrainBoard Member

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    I must admit that did light my eyes up! Good to know the name is appreciated, even though of course now Rolls Royce Cars is wholly owned by the German car giant BMW. Us Brits only have the Aero engine part of Rolls Royce.
     
  9. Jimbo20

    Jimbo20 TrainBoard Member

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    Yes - here in the UK our household mains supply is called 'Live' (US hot) and 'Neutral' (US ground). Our 'Earth/Ground' is a third connection and is literally a connection to the copper household plumbing, and must never be shorted/connected to neutral. Being 230 volts AC leaves less room for mistakes compared to 110V :eek:
     
  10. acptulsa

    acptulsa TrainBoard Member

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    Here "live" means the breaker is on, and it can reach out and grab you. And ground and common more properly mean the leg carried through the metal chassis of the device. Which isn't always negative, so I should have said positive and negative.

    But, hardcoaler, you don't need to figure out which leg is which. It should work either way.
     
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  11. TwinDad

    TwinDad TrainBoard Member

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    In the (modern) US, the wires are Hot (black), Neutral (white), and Ground (green or bare). Ground is fed back to a central point in the main box, then grounded directly to earth. Neutral is also tied to (earth) ground at the main box.

    Polarizing a 2-prong plug on a device with a 120V feed (like a light bulb) is supposed to help ensure that the switch is in the hot lead. This, then, "ensures" the bulb socket isn't floating at 120V when "off".
     
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  12. Hardcoaler

    Hardcoaler TrainBoard Member

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    Good news -- y'all nailed it. I set up a test on my bench and it works as directed. I took some photos for the fun of it. Thanks again everyone!

    Off Position:
    2018-06-29 DS&N Toggle Switch Wiring - Off Position - for upload.jpg

    On Position:
    2018-06-29 DS&N Toggle Switch Wiring - On Position - for upload.jpg
     
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  13. Point353

    Point353 TrainBoard Member

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    Why would you not simply plug everything from the layout into a switched power outlet strip?
     
  14. Hardcoaler

    Hardcoaler TrainBoard Member

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    It'd look unfinished, with the power strip and cords hanging down or laying on the floor. I enjoy woodworking and in retirement, finally have the time to attend to nice detail. Even though, my previous layout had a convenient master switch too, as seen on the left panel.

    2017-12-19 DS&N Control Panel - for upload.jpg

    This is the panel for my new road, made of oak and black laminate, and nearly ready for toggle switches and wiring:

    2018-06-08 DS&N Control Panel - for upload.jpg
     
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  15. Point353

    Point353 TrainBoard Member

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    Then get a power strip with a remote switch, such as this one:

    [​IMG]
     
    Last edited: Jul 1, 2018
  16. Kitbash

    Kitbash TrainBoard Supporter

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    The additional pole is probably a line side neutral connection for the light. The light will need a 125V reference, therefore, lineside phase to neutral will be 125v to make the light operate. That would be my "guess".. And it is only a "guess". However, a 40 year old toggle isn't worth it. I like the suggestion above regarding a power strip with a remote on/off switch. Don't mess around w/ 125V. A 40 year old toggle isn't worth the risk.
     
  17. acptulsa

    acptulsa TrainBoard Member

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    What, exactly, is the risk? Did it get metal fatigue sitting in a drawer? Do toggles spoil if not refrigerated? Does it have a 'best if used by' date?

    I shudder to think what would happen to the old car hobby if everyone had your attitude toward new old stock parts.
     
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  18. Jimbo20

    Jimbo20 TrainBoard Member

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    In fact it is known in old car circles that certain 'new - new' stock car parts are downright dangerous - I'm thinking of items such as stop light switches that burst open or fuse holders that melt etc.... I'd much prefer to use new old stock electrical parts on my old car - providing of course they are suitably tested before use.
     
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  19. acptulsa

    acptulsa TrainBoard Member

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    There is something to be said for NOS parts. Generally the lousy designs get used up replacing equally lousy original parts. It's mostly the good replacement parts that sit in a dusty box for decades waiting for identical originals to fail.

    Of course, some of us are old enough to remember blenders, steam irons and Lionel trains serving faithfully for fifty years, before being replaced by Chinese-made items that last fifty months.
     
    Last edited: Jul 1, 2018
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  20. DD99

    DD99 Guest

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    Also so the centre post inside the light socket is "hot", while the outside of the socket isn't...
     

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