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240V LED lamp autopsy.

C

Clive Mitchell

Jan 1, 1970
0
Just got a BC (bayonet cap) base "warm white" LED lamp. So took it to
bits....

The case is superb. The golf ball dimple lens is screwed and glued into
a stout plastic base with a sealing o-ring to make it waterproof.
Another o-ring keeps the LED module in place inside. With modest
pressure you can unscrew the cap to access the guts for analysis.

The LED module is a plastic ring with an LED PCB and a power PCB. The
power PCB is heat riveted onto the back of the plastic ring and the LED
PCB seems to be a push fit, but is retained by it's two wires which are
soldered through into the power PCB.

The LED PCB is simply a neat series circuit of 18 warm white LEDs. Well
assuming you think that greenish white is warm! It's more like the
colour of an old gas lamp. :) Two uncropped LED leads go through
into the power PCB and are soldered to pads

The power board is a traditional capacitive dropper as used in a couple
of LED projects on my site. It has a 220n capacitor with a 1M discharge
resistor, a 390 ohm inrush limiting resistor, a discrete bridge and a
100 ohm LED limiting resistor. There's no electrolytic to smooth out
flicker, but I can't say I noticed any. A fuse has been resined into
the base of the lamp as referenced on the box... "The fuse is inside in
order to protect aganist shortout."

The power PCB has a rectangle routed out to allow the capacitor to sit
through the PCB for space saving. I guess this same module might fit
into an MR16 type shell. The components are all inside the plastic ring
with just the solder side of the PCB in view. The two flying
connections from the base are just soldered onto two pads.

The LEDs are the short 5mm type with the chip directly under a flat lens
to give a very wide output. This through the dimpled lens makes a very
nice pattern on the surface of frosted globes since the many light
sources create a rippled effect through the multiple lenses. The lamp
rating is 1.3W and the life is rated at 60,000 hours up. (Uh huh?)

As a decorative lamp it's not bad at all.
 
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