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Power rating of LED bulb
3

Power rating of LED bulb

Power rating of LED bulb

(OP)
Hello,

I recently purchased a 1 Watt Mains LED light bulb (240V, 50Hz)

Using a 220R resistor in series with the live (hot) line i looked at the current entering the bulb using the scope.

The bulb is said to be 1 Watt but i calculated that the RMS of the input current waveform was 8.75mA...

...this gives a power of 2.1W.

Do you think that they have made a mistake with their power rating of this bulb ?

..here is the current waveform from the mains into the bulb...

[IMG]http://i44.tinypic.com/6h8gtg.jpg[/IMG]

RE: Power rating of LED bulb

Read up on power factor. It is entirely possible for the condition you describe to occur.
  

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If we learn from our mistakes I'm getting a great education!
 

RE: Power rating of LED bulb

About a week ago, I bought a "7 watt" mains-powered LED light bulb at the Dollar Store.

The bulb isn't really 7 watts. Further inspection reveals four diodes in a bridge and a half-watt (!) series resistor. I'm not surprised in the slightest. New saying: "Lies, d*mn lies, and dollar store packaging."

 

RE: Power rating of LED bulb

(OP)
Thankyou all for replying,

VE1BLL....glad to hear yours only cost a dollar....my "1 Watt" LED bulb cost me £9.33 and took 2 weeks to arrive by post (an extra £3.50 packaging = £12.83 total)

....when i took it apart, i found the electronics was pretty much just a 220nF series cap dropper and a diode bridge, + 4 LEDs....it also had a series 100R resistor.

and i had to smash it to get inside, so its useless now.

Anyway, do you think i will have to first calculate the fundamental of the above current waveform and then get the RMS of that to find the real power consumed ?

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