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Pete C.

David Billington wrote:

Pete C. wrote:
wrote:

I have a bedside lamp with a 100W halogen lamp which runs directly off
110V. In the base of the lamp is a small rotary switch about 3/4" in
diameter. It has three positions: Full intensity, reduced intensity
and off. No other parts are discernible.

The question is: How does the lamp achieve the reduction in light
intensity (about half)?

I actually know the answer because I took the switch apart but when I
was looking for it before on Google etc. I could not find it.

I am posting here to see how widely this trick is known.

A diode. Cut out half of the AC cycle and get reduced brightness. Very,
very common, indeed there are/were little socket insert disks made that
you stuck in a light socket to save power.

A friends son has a filament lamp which has 3 intensities and off and
cycles between them when you touch the metal lamp base itself, no switch
just contact. How would that be done.

Simple touch switch controller, uses several fixed levels of regular
triac phase control for the dimming. You can buy the control module for
like $5 to add to any lamp that has some metal surface you can use for
the touch switch.