In article ,
"Sylvain VAN DER WALDE" writes:

Please tell us about dimmable ballasts.
Any websites?

There are plenty of dimmable electronic ballasts. They don't use
conventional filament lamp dimmers though.

Simplest is the type which use a 0-10V DC control voltage, and
most ballasts produce a low current 10V supply so you can do
this with just a simple low power potentiometer if you're just
controlling the one ballast, although you'll need a separate
10V supply if you're ganging several ballasts to dim together.
This method is now regarded as out of date.

There are also DSI and DALI digital interfaces which use a low
voltage serial digital signalling interface between a controller
and the ballasts.

Some ballasts support multiple methods, e.g. DSI and simple
push-button up/down dimming.

I don't know of a supplier. I have used Burnlite, but they now
say they won't supply the public anymore (although I haven't
actually tried since then). Of course a recession in the building
trade might change their minds. Make sure you're sitting down
when you get the prices -- dimming ballasts are pretty much only
used in top-end expensive commercial installations, and are not
price sensitive commodity items.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]