How Do You Light The Neon In A Rocker Switch ?

Started by Incubus, July 22, 2005, 12:05:22 PM

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Incubus

I've got a small rocker switch with a neon in it. I've wired into my power amp, and the the switch works, but the neon isn't lighting.

It has 3 lugs on the back and they're in this configuration:

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The switch lugs are the 2 on the left which are above eachother. These have a wire coming from the fuse connected to 1 lug, and the wire from the other lug goes to the mains transformer.

The 3rd lug on the bottom right has no wires connected to it.

My guess is that the 3rd lug needs to be connected to neutral from the mains lead.

Can anyone just confirm this for me.....FWIW I'm in Australia so it's 240V ac.

zachary vex

well, i don't have one of those types of switches handy, but i can guess that the impedance involved is so high that you can't make a mistake connecting that lug to almost anything... just test with the power off first to make sure it's not an extra throw on the switch, or shorted to one side or the other directly.  if your meter says the resistance to that spare lug is very high (or likely it will read open) then connect it to various points until you get a result.

point number 2:

if that switch was removed from service (from some other piece of gear) keep in mind that many tiny neon bulbs have very limited life.  eventually, they begin to flicker, and then die.  flickering ones are interesting... if you shine a light on them, they'll light up just fine... but if you take it away, they'll flicker again.  try it!  it's always the power strip under the desk that has the flickery light on the switch... shine a flashlight on it, and voila, it's lit again!

Peter Snowberg

The big question is whether or not the switch has a dropping resistor in it?

If it doesn't, connecting the 3rd terminal to neutral without a dropping resistor will cause a nice little (contained, hopefully) explosion.

Some switches are made so that the indicator can be run from 110 or 220V.
Eschew paradigm obfuscation

Incubus

Well, I connected that 3rd lug to the Neutral wire and it works fine.

I should have added a little info in the original post.

It's a new switch, SPST, I checked with a multimeter and the 2 lugs above eachother were reading open in one switch position and zero ohms in the other switch position which is how I knew these lugs were actually for the switch.

The 3rd lug read infinite ohms no matter whether the switch was set to "On" or "Off", which is why I thought the lug was not connected.

The other thing I assumed was that neons work by being in series with the Active wire.....like the fuse and the switch.

Found out it's actually parallel across the primary of the transformer.

Looks kinda cool....I have the neon telling me that 240V is present, and I've got a blue LED next to it which tells me that the power supply +40V dc is being produced.