OT Ask EU: LEDs again

[BrritSki]

After making the wreath I had some leftover bits of beech mast twigs,
holly, fir and "snow"-anointed teasel heads. so I made a window
decoration in a vase and as a final touch I added a string of wine
bottle LED lights. This was the odd string in the pack. All the others
were pastel shades whereas this had red and green LEDs which went well
with the theme, as well as a couple of blues and yellows.

The interesting thing is that when they've been on for a bit. All of the
lights except green go out. It's not a battery issue as I changed them,
and if you turn them off again for a while they all come back on.

ISTR that some colours are harder to create than others, but maybe it's
just a temperature issue.

Thoughts ?

[Sam Plusnet]

Post by BrritSki
After making the wreath I had some leftover bits of beech mast twigs,
holly, fir and "snow"-anointed teasel heads. so I made a window
decoration in a vase and as a final touch I added a string of wine
bottle LED lights. This was the odd string in the pack. All the others
were pastel shades whereas this had red and green LEDs which went well
with the theme, as well as a couple of blues and yellows.
The interesting thing is that when they've been on for a bit. All of the
lights except green go out. It's not a battery issue as I changed them,
and if you turn them off again for a while they all come back on.
ISTR that some colours are harder to create than others, but maybe it's
just a temperature issue.
Thoughts ?

Odd that.
Some colour LEDs need a higher voltage to operate that others, so as the
batteries start to droop (Oh-err Missus!) some colours dim & drop out in
a consistent order.
Maybe, when you switch them off, the batteries manage to catch their
collective breath & decide to play ball for a while longer?

[J. P. Gilliver (John)]

Post by Sam Plusnet

Post by BrritSki
After making the wreath I had some leftover bits of beech mast twigs,
holly, fir and "snow"-anointed teasel heads. so I made a window
decoration in a vase and as a final touch I added a string of wine
bottle LED lights. This was the odd string in the pack. All the others
were pastel shades whereas this had red and green LEDs which went well
with the theme, as well as a couple of blues and yellows.
The interesting thing is that when they've been on for a bit. All of
the lights except green go out. It's not a battery issue as I changed
them, and if you turn them off again for a while they all come back
on.
ISTR that some colours are harder to create than others, but maybe
it's just a temperature issue.

It took the semiconductor industry longer to create some colours - they
did red first, then orange, yellow, green, finally blue (on the way,
they also developed ones that emit infra-red - most remote controls use
those - and ultraviolet). (They never did make ones where the LED
actually emits white: "white LEDs" are actually blue/UV, but have
phosphor in them that absorbs blue/UV and glows white.) But once they've
been made, there's little difference in reliability between colours.
Though there _is_ ...

Post by Sam Plusnet

Post by BrritSki
Thoughts ?

Odd that.
Some colour LEDs need a higher voltage to operate that others, so as
the batteries start to droop (Oh-err Missus!) some colours dim & drop
out in a consistent order.
Maybe, when you switch them off, the batteries manage to catch their
collective breath & decide to play ball for a while longer?

... that; red ones work on about 1.6-1.8V, green and yellow about
2.2-2.3V, and blue need up to about 5V. So if it was purely that, I'd
expect red to be the last on. But the electronics in the box convert the
battery voltage to the voltages required by the various colours anyway,
they're not all connected in parallel; if you connected a red LED to the
voltage needed to light a blue one, it'd go pop. So the fault is in the
electronics in the box.

[Mike]

Post by J. P. Gilliver (John)

Post by Sam Plusnet

Post by BrritSki
After making the wreath I had some leftover bits of beech mast twigs,
holly, fir and "snow"-anointed teasel heads. so I made a window
decoration in a vase and as a final touch I added a string of wine
bottle LED lights. This was the odd string in the pack. All the others
were pastel shades whereas this had red and green LEDs which went well
with the theme, as well as a couple of blues and yellows.
The interesting thing is that when they've been on for a bit. All of
the lights except green go out. It's not a battery issue as I changed
them, and if you turn them off again for a while they all come back
on.
ISTR that some colours are harder to create than others, but maybe
it's just a temperature issue.

It took the semiconductor industry longer to create some colours - they
did red first, then orange, yellow, green, finally blue (on the way,
they also developed ones that emit infra-red - most remote controls use
those - and ultraviolet). (They never did make ones where the LED
actually emits white: "white LEDs" are actually blue/UV, but have
phosphor in them that absorbs blue/UV and glows white.) But once they've
been made, there's little difference in reliability between colours.
Though there _is_ ...

Post by Sam Plusnet

Post by BrritSki
Thoughts ?

Odd that.
Some colour LEDs need a higher voltage to operate that others, so as
the batteries start to droop (Oh-err Missus!) some colours dim & drop
out in a consistent order.
Maybe, when you switch them off, the batteries manage to catch their
collective breath & decide to play ball for a while longer?

... that; red ones work on about 1.6-1.8V, green and yellow about
2.2-2.3V, and blue need up to about 5V. So if it was purely that, I'd
expect red to be the last on. But the electronics in the box convert the
battery voltage to the voltages required by the various colours anyway,
they're not all connected in parallel; if you connected a red LED to the
voltage needed to light a blue one, it'd go pop. So the fault is in the
electronics in the box.

Rather sounds as if the battery you used to replace the previous one was
composed of tired cells or maybe a single cell going down Brittski. Jpeg
confirmed my sauce pisions; I have observed that when the rechargeable
cells in our garden lights are running low, red is the colour that hangs on
to the bitter end.

[Penny]

On Thu, 26 Dec 2019 08:10:18 +0000, "J. P. Gilliver (John)"

Post by J. P. Gilliver (John)

Post by Sam Plusnet

Post by BrritSki
After making the wreath I had some leftover bits of beech mast twigs,
holly, fir and "snow"-anointed teasel heads. so I made a window
decoration in a vase and as a final touch I added a string of wine
bottle LED lights. This was the odd string in the pack. All the others
were pastel shades whereas this had red and green LEDs which went well
with the theme, as well as a couple of blues and yellows.
The interesting thing is that when they've been on for a bit. All of
the lights except green go out. It's not a battery issue as I changed
them, and if you turn them off again for a while they all come back
on.
ISTR that some colours are harder to create than others, but maybe
it's just a temperature issue.

It took the semiconductor industry longer to create some colours - they
did red first, then orange, yellow, green, finally blue (on the way,
they also developed ones that emit infra-red - most remote controls use
those - and ultraviolet). (They never did make ones where the LED
actually emits white: "white LEDs" are actually blue/UV, but have
phosphor in them that absorbs blue/UV and glows white.)

And guaranteed to provoke a migraine in me, as I discovered recently when I
bought some new solar-powered motion-sensor outdoor lights and used one in
the hallway for a few days. I'm very glad I didn't go for the LED option
when replacing a fluorescent tube the other day.

Post by J. P. Gilliver (John)
But once they've
been made, there's little difference in reliability between colours.
Though there _is_ ...

Post by Sam Plusnet

Post by BrritSki
Thoughts ?

Odd that.
Some colour LEDs need a higher voltage to operate that others, so as
the batteries start to droop (Oh-err Missus!) some colours dim & drop
out in a consistent order.
Maybe, when you switch them off, the batteries manage to catch their
collective breath & decide to play ball for a while longer?

... that; red ones work on about 1.6-1.8V, green and yellow about
2.2-2.3V, and blue need up to about 5V. So if it was purely that, I'd
expect red to be the last on. But the electronics in the box convert the
battery voltage to the voltages required by the various colours anyway,
they're not all connected in parallel; if you connected a red LED to the
voltage needed to light a blue one, it'd go pop. So the fault is in the
electronics in the box.

I'm a bit confused by the thought the blue (and presumably the white)
require a higher voltage (though it was probably when failing to understand
electrickery that I hit my 'I can't do physics' wall). I bought a cheap
string of solar-powered blue lights. Although the battery box is designed
to hold 4 AA batteries it is only wired for 2 so the lights don't stay on
very long - they might stay on 'til bedtime in the summer. Had I chosen a
different colour would they be lit for longer?

Then there's the colour changing light-on-a-stick which cycles through
blue/red/green and only has one bulb...

[J. P. Gilliver (John)]

Post by Penny
On Thu, 26 Dec 2019 08:10:18 +0000, "J. P. Gilliver (John)"

[]

Post by Penny

Post by J. P. Gilliver (John)
those - and ultraviolet). (They never did make ones where the LED
actually emits white: "white LEDs" are actually blue/UV, but have
phosphor in them that absorbs blue/UV and glows white.)

And guaranteed to provoke a migraine in me, as I discovered recently when I
bought some new solar-powered motion-sensor outdoor lights and used one in
the hallway for a few days. I'm very glad I didn't go for the LED option
when replacing a fluorescent tube the other day.

Odd, since fluorescents use phosphors too (which fluoresce, hence the
name) - and for the same reason: the light source (semiconductor "chip"
in the LEDs, spark along the length of the tube for fluorescents) puts
out most of its light energy in the part of the spectrum we don't see,
and the phosphor makes it visible. I guess they are spectrally
different, though; white LEDs _mostly_ _do_ look bluer, I agree. I say
mostly, because "warmer" white LEDs are starting to appear: the little
desk lamp I have (Lidl, telescopic, _not_ magnifying) I'd swear had a
filament bulb if I didn't _know_ it was LEDs.
[]

Post by Penny
I'm a bit confused by the thought the blue (and presumably the white)
require a higher voltage (though it was probably when failing to understand
electrickery that I hit my 'I can't do physics' wall). I bought a cheap
string of solar-powered blue lights. Although the battery box is designed
to hold 4 AA batteries it is only wired for 2 so the lights don't stay on
very long - they might stay on 'til bedtime in the summer. Had I chosen a
different colour would they be lit for longer?

You'll probably find that box does more than just _hold_ the cells; it
(or some other innocuous-looking part of the system) almost certainly
contains a little lump of electronics that converts the battery voltage
(over quite a range, too, probably) to what the LEDs require. If you
shake your head when viewing the lights in near-dark (so that the lights
make a streak of light on your retina/brain, like when you wave
sparklers around)), you'll probably see they're not on steadily, but
flashing very fast. If so, that'll confirm they're running from a
"switched-mode power supply" (SMPS) that changes the voltage. [Note that
the solar-powered cats' eyes that are appearing in a lot of our
motorways and 'A' roads are ditto; you can see the dotted trail as you
pass them.]

Post by Penny
Then there's the colour changing light-on-a-stick which cycles through
blue/red/green and only has one bulb...

That "bulb" will actually contain at least a red, green, and blue LED,
plus the electronics to fade them up and down in various combinations.
(The actual chips in LEDs are very small - a millimetre or two, except
for really powerful ones - meaning they can be placed so close together
you can't tell they're not one source, especially if there's any sort of
diffuser [milky housing].)