I would guess the Leds have a Cheap 1N4004 diode connected in series with them,
so they aren't damaged by the possible large reverse voltage, or they may be
connected in pairs back to back so one LED conducts on one half of cycle and
the other on the other half cycle. They must also include a current limit of
some sort, probably just a small resistor potted into the connector. In
theory a triac dimmer should work over part of its range if the string uses
with a current limit resistor, but it may be the current draw (probably ~20mA)
is so low the dimmer circuit itself will not function properly.
If it were me I would just try it.
You could also try connecting a small incandescent light in parallel with the
light string, to increase the load a bit for the dimmer to operate on.
tim Hughes
--- On Mon, 12/15/08, Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx> wrote:
> From: Chuck Norcutt <chucknorcutt@xxxxxxxxxxxxxxxx>
> Subject: Re: [OM] [OT] LED Christmas lights and an incandescent dimmer???
> To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
> Date: Monday, December 15, 2008, 7:54 PM
> Thanks, but I think I'll just go buy an inline switch.
> :-)
>
> Chuck Norcutt
>
> WayneS wrote:
> > Then I don't see why a dimmer should not work. The
> string probably
> > has enough in series to drop 120VAC, and the natural
> diode
> > action means they only use 1/2 of the cycle. the
> diodes must have
> > good reverse voltage breakdown. Peak voltage is 163V.
> divide by two and
> > you get 80 bulbs in series.
> >
> > The dimmer effect may be a bit non-linear, but should
> work.
> >
> > Wayne.
> >
> > At 07:24 PM 12/15/2008, you wrote:
> >> These LEDs connect directly to the 120v supply.
> There is no visible
> >> converter. The plugs are even normal size for an
> incandescent string of
> >> lights so I don't think there's anything
> hiding in there except a fuse.
> >> They look exactly like a normal string of small
> incandescent bulbs
> >> except that they're LEDs. The bulbs also pop
> in and out of sockets like
> >> they would if they were small incandescent bulbs.
> Bulbs are stated to
> >> be 2 volts and 0.04 watts. A box of them consists
> of either 2 strings
> >> of 90 bulbs or 3 strings of 60 bulbs for 180 bulbs
> drawing only 7.2 watts.
> >>
> >> Chuck Norcutt
> >>
> >> WayneS wrote:
> >>> LEDs are DC so there must be an AC to DC
> converter. Without knowing
> >>> the details of that converter it may, or may
> not work.
> >>>
> >>> Wayne
> >>>
> >>> At 04:56 PM 12/15/2008, Chuck wrote:
> >>>> What happens if I plug my LED Christmas
> tree lights (120v) into an
> >>>> incandescent dimmer switch? ...
> >
> >
> >
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