On 05/04/16 10:40, Syd Rumpo wrote:
On 04/04/2016 19:48, wrote:
On Monday, 4 April 2016 17:29:50 UTC+1, T i m wrote:

So, assuming the first LED lamp I tried was also non-dimmable and
seems to work fine, what is it about 'dimmable' that makes them so

RC power supply

please. Would there be any issues using non-dimmable LEDs with a
dimmer like that if they actually seem to work ok or could it cause
the lamp to fail prematurely or worse?

immediate failure or fire due to severe overheating of the power
supply resistor.


NT

Just for info...

I took one apart - it was 4.5W golfball (30W equivalent) and supposedly
not specifically dimmable, but I guess it would.

There was a series input capacitor feeding a full wave bridge with an
electrolytic reservoir capacitor on the DC side, then 50 ohms to a
series string of 14 white LEDs on a separate PCB. Plus other high value
resistors as bleeders.

The LED PCB was well gunked onto an aluminium heatsink with thermal
grease. Simple but it worked.


And I think that is the key to why LED bulbs are pretty good. The
circuitry is much simpler than the CFLs.

And, sticking what amounts to a capacitative load on the mains is going
to make the Grid happy, to offset all those inductive loads in motrs etc.

But because its a capacitative load, don't except dimmers to behave as
expected.


Cheers


--
You can get much farther with a kind word and a gun than you can with a
kind word alone.

Al Capone