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Adding a pilot light to a 3-way switch

Discussion in 'Electronic Design' started by John Smith, Jun 10, 2008.

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  1. John Smith

    John Smith Guest

    I need a stack switch with one standard switch and one 3-way switch with
    a pilot light. I called the electric supply warehouses around town and
    found none. They do carry one without the pilot light. It looks like I
    have to add the pilot light myself.

    I believe what I need is a 120 V diode with a really small amperage,
    less than 1 mA if possible. Is that correct? I haven't thought about how
    to wire it. I have the impression that that part should not be too

    Thanks for any help.
  2. James Sweet

    James Sweet Guest

    I would use a small neon panel lamp mounted in the corner of the switch
    plate. Keep in mind there may be code issues with anything of this
    nature so check local codes and do not proceed unless you know what
    you're doing. How to wire it depends on how the circuit is laid out, but
    you need one side to the neutral, and one side to the hot wire out to
    the light.

    You can also get a pilot light which is designed to hold a standard C7
    incandescent lamp and mounts in place of a wall switch, you could use an
    LED retrofit lamp in one of those, but it would require an additional
    gang in the junction box or a separate box. Again this isn't something
    you should try yourself if you aren't sure.

  3. I don't think he can put a pilot light in a 3-way switch. The circuit will
    become unstable because two hot leads have to be connected to the pilot
    light. I suppose a couple of diodes could keep the circuit stability intact.

    Having said that, I'm on board with the neon light too.
  4. James Sweet

    James Sweet Guest

    Well like I said, it depends on how the circuit is laid out. In my house
    power comes in and the wire goes out to the light from the same box,
    then a 3 conductor cable runs from that box to the remote switch, so
    adding a pilot to the master switch is easy, adding it to the remote
    switch would require an additional wire. I've seen some 3 way
    arrangements where power enters at one switch box and the light comes
    off the other switch, as well as one that had power entering the light
    fixture box and then a separate switch drop, that's the hardest to add a
    pilot to.

    I don't know where you're going with the stability and diodes thing,
    none of that is necessary, you wire the pilot light up across the wires
    going out to the light fixture. Perhaps you're thinking of an
    illuminated switch? That's different than a pilot light, though it could
    also be added if things are laid out favorably.

  5. Yes, I was thinking of an illuminated switch. Isn't that a pilot light?

    What's a pilot light if not an illuminated switch?
  6. James Sweet

    James Sweet Guest

    A pilot light illuminates when the switch is on to let you know that a
    remote light is on, an illuminated switch lights up when the light is
    off so you can find the switch in the dark.

  7. Okay, I get it.

    I was thinking of an illuminated switch so one could find it in the dark.
  8. No idea about the OP's question, wonder why he used Chinese encoding in his
    post. In Greece, we call 3-way switches aller-retour (French), and there's a
    design with 3 switches, 2 3-way and 1 4-way.
  9. bud--

    bud-- Guest

    Sounds like an illuminated switch (lighted when off) might work. I
    believe illuminated 3-ways connect a neon lamp between the travelers.

    If a commercial combination is not available one way to do this in a
    single opening is to use Despard devices, which are interchangeable
    devices that mount on a strap with 3 openings. You could combine a
    standard switch, a 3-way switch and a *neon* pilot light unit. Wire the
    neon light across the 3-way travelers. You could have a light at each
    end. The light will be on when the switched load is off. There needs to
    be some load to light the neon light. Google for Despard.
    If you are at the load-end 3-way, and a neutral is available, you can
    connect the light across the load as a pilot light.

    I would not recommend do-it-yourself. You might be able to find space
    for a UL listed commercial pilot light unit with leads.

    You could try the question at There are several good
    electricians and some other sharp people. Someone might know of a
    commercial device.
  10. Rich Grise

    Rich Grise Guest

    Then go back to the light switch store and tell the guy that that's
    what you were looking for in the first place. Tell him, "Oops!". :)

  11. Tim Shoppa

    Tim Shoppa Guest

    Look in the catalogs... e.g. Hubbell HB1203PL. Stock item at Grainger
    and probably at the big electrical suppliers if you give them the part
    number :).


  12. I'm not the one that was asking for it, I'm one of the people that attempted
    to give an answer based on my false assumption/misunderstanidng of the
    device being sought.
  13. John Smith

    John Smith Guest

    Thanks to all of you who replied to my question.

    I think I'll settle with a neon lamp since it's easy to find 120v neon
    lamps while 120v LED is hard to find.

    I'm replacing an existing standard switch with two 3-way switches so I
    can control the attic fan from 2nd floor also. That means I can decide
    which is the rightmost and leftmost switch in Guy's drawing (BTW, thanks
    for taking time to draw the diagram).

    So, the hot of the rightmost switch goes to, in addition to the attic
    fan, a 47K Ohm resistor, a neon lamp then to the neutral of the other
    switch (the standard switch in the stack switch) because the 3-way
    switch doesn't have a neutral.

    Thanks again to everyone.
  14. James Sweet

    James Sweet Guest

    Just get a neon lamp which is already a finished assembly with a
    resistor and all, you can pick them up at Radio Shack among other
    places, then just drill a hole and mount it. If you're adding the second
    switch yourself, you can run an additional wire to put the pilot light
    in either or both locations.

    You can also get thermostats designed specifically to run attic fans
  15. bud--

    bud-- Guest

    If there is a load (like a light bulb or fan), and the switches are in
    an off combination, there will always be 120V between the travelers (the
    2 wires connecting the switches). A neon light connected between the
    travelers will light up. That works at both ends. It works when 4-way
    switches are added. It works when wired with the with the less common
    "California 3-way" setup.

    Despard devices *are* "standard devices" available from several
    manufacturers. They have been around for a real long time. Even Roy can
    find them.
  16. Guest

    | Years ago I added a pilot light to a similar situation at my parent's
    | house. See thus:
    | O----------O O----------O
    | / | / \
    | HOT-----O | / O-----(LIGHTS)--
    | | / |
    | O----------O O----------O | 3-WAY
    | | | |
    | R R |
    | | | |
    | +___+ |
    | | |
    | NEON |
    | | |
    | NEUTRAL---------+-------------------------------------
    | Resistors "R" were around 100k, and the neon light an NE-2 equivalent.
    | When the lights are off, the neon light sees 1/2 the line voltage,
    | divided by the resistors. When the lights are on, then one of the
    | resistors floats (except for capacitance of the wiring), and the other
    | drives the neon light. This depends on the non-linearity of the neon
    | light: at 1/2 line voltage it either fails to light, or just barely comes
    | on.

    Why not just wire the neon light directly between the two wires you have
    the resistors on, with the appropriate ballast resistor, and not connected
    to the neutral at all?
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