On Wednesday, 14 March 2018 15:05:51 UTC, NY wrote:
"whisky-dave" wrote in message
...
On Wednesday, 14 March 2018 10:18:33 UTC, Tim Watts wrote:
On 14/03/18 09:54, whisky-dave wrote:

But it is true the problem with LED lightbulbs is that they do get very
hot at the base as that's where the SMPS are but the heat can be
transfered to the actual LEDs which don;t like being hot.
The life of the lamps might well be UP TO 15K hours but they are very
liklely to fail long before that due to temperature as the 15K hours
refers to an LED used within the specs and even then it doesn't mean it
will last 15,000 hours.



Not all LED lamps have much in the way of PSUs

https://youtu.be/ReO9D1E8XqI?t=9m2s

Basically a bridge and 3 passives.

They canlt easily be dimmed, they are crap, they flicker and don't last
anywhere near as long as stated.

They can be dimmed very easily using their own built-in control logic

what built in control logic ?
How do they dim rising or falling or just increased resistance ?


(but
not too effectively by using an external triac dimmer) - all that is
required is a constant-frequency square wave with a variable mark:space
ratio.

The problem is that they tend to be clocked at a relatively low
speed, so as you decrease the M:S ratio, the flicker on moving objects
becomes very noticeable.

Yes I know, but of course others have said there's no flicker.


I've seen some 7-segment LED displays on cookers which were clocked at main
frequency, and that was *horrible* if your eye panned over something moving
and you saw multiple copies of the time in your field of view. Likewise for
the "red man" on the switch box of a Pelican crossing as you are driving
past.

We have bench PSUs here that do the same but that is because of multiplexing displays and nothing to do with mains frequency.