12V MR16 led lamp that isn't

[Andy Wood]

So I was in a "two dollar" store and I saw that they had various cheap LED
lamps. Out of curiosity, I bought one, described by the packaging as "12V
MR16 1W 18LED", for $3.99. It looks like a typical MR16 lamp, but yes it
does have 18 leds.

I tried it first on 12 volts DC, and then on 12 volts AC, but there was not
even the faintest glimmer. OK, so it could have just been doa, but as it had
been my intention to pull the thing apart, I proceeded to do that anyway.

Besides the 18 leds, there are four other components - a 1k resistor, a 1M
resistor, a 0.15 microfarad 400V capacitor, and a bridge rectifier. All 18
of the leds are connected in series across the output of the bridge
rectifier. The first input to the bridge comes from one of the power input
wires through the 1k resistor. The second input to the bridge comes from the
other power input wire through the capacitor, which has the 1M resistor
connected in parallel across it.

In short, there is no way this is going to work on 12 volts. My guess is
that the guts of this thing belong in a GU10 lamp that operates directly
from the mains. I have to wonder if they also ended up with GU10 lamps with
the MR16 boards in them.

 

[Ian Field]

"Andy Wood" <woodag@trap.ozemail.com.au> wrote in message
news:iaWdnb5NALDvKcfTnZ2dnUVZ_qadnZ2d@westnet.com.au...

So I was in a "two dollar" store and I saw that they had various cheap LED
lamps. Out of curiosity, I bought one, described by the packaging as "12V
MR16 1W 18LED", for $3.99. It looks like a typical MR16 lamp, but yes it
does have 18 leds.

I tried it first on 12 volts DC, and then on 12 volts AC, but there was
not even the faintest glimmer. OK, so it could have just been doa, but as
it had been my intention to pull the thing apart, I proceeded to do that
anyway.

Besides the 18 leds, there are four other components - a 1k resistor, a 1M
resistor, a 0.15 microfarad 400V capacitor,

So called "wattless dropper" - Xc is high compared to Rl so I is for all
intents & purposes constant, or I leads V so it fools your electricity meter
as to how many W you're using.