Re: Dimmable Fluorescent Lights (again)

[Richard Malcolm-Smith <rich@xxxxxxxxxx>]

christopher purves wrote:

> Hi,
>
> I need to find a UK supplier of replacement ballasts (DSI enabled) for
my
> fluorescent lights (the tubes are rated at 36w if it matters).
>
> While we are at it, can anyone explain what the various components of
a
> fluorescent setup are.
>
> I can see the tube, the starter motor, the ballast (looks like a
> transformer) and what looks like a giant capacitor.
>
> Any and all help appreciated.

The capacitor is there to help correct the power factor - not needed in a
domestic situation where there are only a few fittings, and removing it
will
eliminate the x10 signal sucking issue that the fittings have.

The starter is not a motor at all, its a bimetalic switch in a vacuum.
Basically, when the fitting is first turned on, the tube isnt conducting,
so you
have the full 240 volts across the starter. It will have a gas discharge
across
it (purple glow) and that heats the switch, so it closes, allowing current
thru
the heaters at the end of the tube. After a short time (1 second or so) -
the
strip cools because of the lack of gas discharge and it opens again. this
hopefully causes the inductance of the balast to cause an arc to form in
the
tube. If not, the process starts again, and if the tube is had it, it will
keep
going causing the tube to just flicker and not start properly.

When you swap the ballast out (and I have only ever used 0-10v ones myself)
you
will need to connect 2 wires to each end of the tube. This caused problems
for
me on one type of fitting where the starter socket was integraded to the
bulb
holder in between the tubes as there was no direct connection to that pin
of the
tube. In the end we had to pry the sockets open and bypass the starter
socket
and put some epoxy in the hole so noone would try to stick one in.

The only other component of most fittings is a small fuse on the input
terminal
block that will hopefully blow in the event of a balast shorting to earth,
which
isnt too rare.


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