Hi everyone, I'm interested in how one of my lamps with a 2-way switch works. My collegiate lamp uses a two way socket that runs an incandescent or halogen bulb at full brightness and half brightness. At half brightness, the incandescent bulb seems to flicker a little bit.  It's a cool lamp because these two way sockets are not common.

How about posting a photo of the fixture.?

Hi everyone, I'm interested in how one of my lamps with a 2-way switch works. My collegiate lamp uses a two way socket that runs an incandescent or halogen bulb at full brightness and half brightness. At half brightness, the incandescent bulb seems to flicker a little bit.  It's a cool lamp because these two way sockets are not common.

It looks more like a standard single filament lamp, at full power setting connected directly to mains, at the reduced power with a dioe in series. This diode then reduces the voltage to about 70% (rms value), so power to abou half...
This trick was quite popular DYI improvement here here in the 70's and 80's - the wall light switch was replaced by a two switch module, one switching the power directly, second via the diode.
But the problem today is, this does not work with commercial CFL, nor LEDs, for that you would need a special ballast "decoding" the half wave rectification as a command for power reduction, something like this . But I've never seen anything like tat commercially available...

How about posting a photo of the fixture.?

Here's a picture of the lamp.  The socket looks like an ordinary 120 volt lamp socket, but it runs a standard light bulb at two levels of brightness.

It looks more like a standard single filament lamp, at full power setting connected directly to mains, at the reduced power with a dioe in series. This diode then reduces the voltage to about 70% (rms value), so power to abou half...
This trick was quite popular DYI improvement here here in the 70's and 80's - the wall light switch was replaced by a two switch module, one switching the power directly, second via the diode.
But the problem today is, this does not work with commercial CFL, nor LEDs, for that you would need a special ballast "decoding" the half wave rectification as a command for power reduction, something like this . But I've never seen anything like tat commercially available...

Oh cool, reduced voltage.  I had a feeling that was how my lamp worked, especially due to the tiny amount of flicker on the low setting.  Thanks Medved 

If you remove the lamp holder shell, you will probably see the diode. As far as I know, they're not made anymore, I got mine on eBay. It was just the socket internals, I used an existing lamp holder.

When these were popular, they even made an inline rotary (thumb wheel) version with a diode dimmer.

The popularisation of CFL and then LED killed these, like Medved said.

If you remove the lamp holder shell, you will probably see the diode. As far as I know, they're not made anymore, I got mine on eBay. It was just the socket internals, I used an existing lamp holder.

When these were popular, they even made an inline rotary (thumb wheel) version with a diode dimmer.

The popularisation of CFL and then LED killed these, like Medved said.

I've seen some lamps with the thumbwheel two way switch.  Hard to find these days.

Do touch lamps work the same way, by decreasing the voltage for the lower brightness settings?

i had a set of power savers from the 70's that went in the socket between the center contact and the bulb.  they were a diode and sort of looked like a coin with a plastic insulating ring around the outside.  they supported up to 60w lamps but anything over 25 got them hotter than hell.  i had 2 or 3 of them and they all eventually failed by passing current both ways.  i assume a combination of age and heat killed them.  i still have them somewhere...

The diode (what is discussed above) decreases the RMS voltage (what affects the power delivered to an Incandescent or Halogen lamp), but it does so by wiping out parts of the sine wave. Not by proportionally shrinking the wave (as a ballast or stepdown transformer would)

Line voltage and matching power (f momentary power, g average power) without any additional components :



With diode :



The touch lamp is basically a dimmer with few preset levels, and some circuitry to detect the slightest leakage current (the lamp body is live through a very high value resistor). The dimmer blanks parts of the wave according to its setting :

Could you post a picture of the Internals and Externals of said Two way switch? I am Curious...

Could you post a picture of the Internals and Externals of said Two way switch? I am Curious...

Here you go, Owen 

Here you go, Owen 

Interesting, Seems like a hard bird to identify just by looking alone... I kindof want one of these things now... am curious of them....

It almost appears like a Three-way socket but the "additional contact" to the left has a solid lead that appears to run underneath and to the main. That lead could be one leg of a diode.