On 21/12/2020 22:56, Cursitor Doom wrote:
On Mon, 21 Dec 2020 20:57:55 +0000, The Natural Philosopher
wrote:
?
Well I am only guessing, but Id say that the same inductor that limits
tube current limits the LED current and with enough in series you can
make up the voltage, or not, as you prefer. .

I'm really struggling to see how the tube supply would be remotely
compatible with LEDs. Tubes are voltage operated devices,

Well no, they are not. Almost exactly the reverse in fact

The thing about a tube is that it is a gas discharge tube, and needs a
fair voltage to *strike* , and the assistance of some cathode heaters,
but once struck it will draw (almost) unlimited current, at a
(constant) voltage IIRC of about 70. The inductor serves to limit the
current.

Irrespective of what the voltage across the tube is. You could replace
the tube with a dead short and it wouldn't trip anything - the inductor
limits the current.

And what that means is that any fairly low impedance load will get the
same power delivered. By what amounts to a constant current source
comprised of the mains and the inductor. And the fact that the LED and
Fluoro efficiencies are similar, means that an LED array fed by such a
source will draw virtually the same or similar power and be of
equivalent brightness in so doing

I have no idea how that current is apportioned to each LED. Or how many
there are. IIRC a whte LED is 4V or so, so to get to no more than 1090V
you wouldn't want more than 25 in series, and you would need a bridge
rectifier. Or perhaps you could have two chains in opposite polarity, to
make use of each half cycle. flickery tho.

I think I'd run a series of rectifiers and caps to drive different
chains and put the chains in parallel. Hmm. No that doesn't work
....possibly if enough diodes are in series the average v drop evens
out...a you can simply out the chains in parallel



LEDs
current-operated. And as far as I know they still require effective
current-limiting

That is the inductor doing that
to overcome the diode 'knee' effect and thermal
runaway.


If you think about it the curve of a buncch of LEDS in series and a gas
discharge tube are pretty similar.

CFLs flicker, don't come on for ages, take longer to warm up, then die.
How many do you want?

As many as you've got. I like 'em.

Next time you are passing then. I do good coffee also



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