The Shed – September-October 2019

Tungsten lamps
The typical lamp is made from tungsten
wire suspended inside a globe from
which the oxygen has been removed.
You add power and the tungsten wire
glows, giving off light. In a typical lamp
the light is radiated 360 degrees (omni-
directional), which works well when
hanging from the ceiling but not so well
inside a downlight. They are cheap to
produce and if used properly will last
many years.
I have the rugged-service (RS) version
in my outside lights and after 16 years
have only replaced two out of four.
Many of the other tungsten lamps in
the house aren’t used as much and are
still working.

Dichroic
At some stage someone designed these
much smaller lamps (50mm) which
gave more light for less power. Rather
than 360 degrees of illumination the
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allows the light to be directed.
They come in various wattages and

beam angles from 10 to 60 degrees,

along with hot beam or cool beam,

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heat through into the ceiling space.

Like downlights, the insulation needs

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of heat cans over them can reduce the

clearance, which means fewer ‘holes’ in

the ceiling insulation.

As with most things, there is

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turn a crispy shade of yellow after a few

years, to ones where the light can be

directed to where you want it.

The 12V versions use an electronic

transformer to provide a soft start and

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from reaching the lamps.

I hear people complain about them

only lasting a short time. I wonder

where they have been sourcing their

lamps, and if there are some other

issues that are the actual cause, as I

have 26 in my house, with between six

and nine of them on every night, and I

might replace one lamp every two years.

(See later for some common faults.)

A ‘light-emitting

diode’ (LED) is a

piece of silicon that

emits light when

power is applied

Lamp connections twisted

together before connecting

Tungsten v. LED transformer — this tungsten

transformer has multi connectors on secondary

while the LED has a single connection