On Saturday, 16 November 2019 22:30:44 UTC, Commander Kinsey wrote:
On Fri, 08 Nov 2019 11:52:44 -0000, whisky-dave wrote:

On Thursday, 7 November 2019 19:42:55 UTC, Commander Kinsey wrote:
On Tue, 22 Oct 2019 10:58:58 +0100, whisky-dave wrote:

On Monday, 21 October 2019 21:02:48 UTC+1, Commander Kinsey wrote:
On Mon, 14 Oct 2019 13:01:29 +0100, whisky-dave wrote:

On Friday, 11 October 2019 20:08:35 UTC+1, Commander Kinsey wrote:
On Wed, 09 Oct 2019 14:04:03 +0100, whisky-dave wrote:

On Wednesday, 9 October 2019 01:08:01 UTC+1, Commander Kinsey wrote:
On Mon, 07 Oct 2019 12:59:03 +0100, whisky-dave wrote:

On Friday, 4 October 2019 16:34:01 UTC+1, Commander Kinsey wrote:
On Fri, 04 Oct 2019 16:28:06 +0100, whisky-dave wrote:


I just tested one of mine with a meter, and it gave a power factor of 1.00, at 256V, 9.8W.


I doubt that it's just the LED, you shouldn't include the PSU in such calculations especailly if running off mains AC, because you're including the LED+PSU so not really gettign any info about the actual LED.

Why should I not include the whole unit? Surely that's all that matters.

That depends on the statement yuo wish to make.
If you want to test the power factor of an LED then that is what you test for.
If you want to test the power factor of an PSU then that is what you test for.
otherwise the test is pretty meaningless.

All we care about is the power factor of the whole unit. You don't have LEDs on their own.

I do in fact most products have LEDs that aren;t directly connected to mains voltages.
Think or all the LEDS in a TV screen 1000s of them, and in phones.
How about car headlights ?

But what does power factor mean in those circumstances?

Little to the user, but the designer would be interested.

Does it even make sense? Can a DC device even have a power factor?

Yes it can.

What does it mean? I can understand lagging or leading current in AC, but how can that happen in DC?

I't doesn't and that is why it has a power factor of 1 (ONE)

The phase differance between the current & voltage is zero degs, the cosine of zero is one.
In AC the power factor can be up to ONE but not above ONE.

So DC doesn't have a power factor.

At last.

Just up there you said it could.

No.

It's like the pint being half full or half empty that is valid.
But to say the pint is 100% full and there;s for 0% emprty just doesn't make sense and the phrase wouldn't be used.

I've done a similar thing with studetmns in order to teach them.
In one lab they learn how and why a fuse blows.
If they come to me with a blown fuse and ask me for another I give them a blown fuse.
That teaches them the differnce between a blown fuse and a working one.

If I were working in a pub and someone places an empty glass down and says same again, I'd give them an empty pint glass then they'd get the same again as they asked for.