Piddling around with more LEDs

[ehsjr]

Is there Arsenic in old LEDs?

Ouch.

 

[Robert Monsen]

I think candles flicker because of air flow changes.
So you need an air flow sensor.
Could be done by monitoring the voltage over a heated thermistor perhaps.
More air flow, temp drops, voltage changes.

I just built one that is pretty successful, using an LM324, a couple
of diodes, two yellow LEDs, and some resistors. Oh, and a cap.

It amplifies the ac fluctuations of the forward voltage of one diode,
while keeping the dc component the same, and compares it against the
other diode. The second LED is for keeping it lit all the time. I
wrapped both LEDs in a piece of yellow paper. It flickers quite
nicely, and is affected by airflow. It actually looks quite a bit like
a candle if you unfocus your eyes...

One could probably use the Vf of the two LEDs instead of using
diodes...

Regards,
Bob Monsen

 

[Archimedes' Lever]

"I'm not a Brewster! I'm the son of a sea-cook!"

 

[krw]

We have broken the record low for North Central Florida three times
this month. So much for glow-ball warming.

Come on Michael. Aren't you reading what the warmingists in this
group, like Slowman, are saying? Global warming is why it's so
cold. Global warming caused the caps on Mars to grow, lack of sun
spots, and the heartbreak of seborrhea and psoriasis.

 

[Don Klipstein]

Which brings up the obvious questions... Can one use LED indicators
and be RoHS compliant? Is there a RoHS LED?

Digi-Key has 8,884 items for discrete LEDs <75 mA, and 7,894 of them
are RoHS compliant.

(Actual number of different LEDs stocked is less - most come in at least
2 different forms of packaging, with separate catalog numbers.)

Is there Arsenic in old LEDs? Are they RoHS compliant?

Nearly all red, orange, and yellow LEDs prior to the InGaAlP ones that
came out in the mid or maybe early 1990's have arsenic. One older red
chemistry, having peak wavelength 690, 697 or 700 nm and wide bandwidth,
does not.

Apparently includes:

Lumex SSL-LX20465YD (yellow)

Lumex SSL-LX20465ID (A slightly orangish red - known as "high efficiency
red" in the late 1970's and early 1980's).

At least 11 through-hole red Avago LEDs are currently in Digi-Key's online
catalog, and have wavelengths and brightnesses typical of GaAlAsP (or
whatever it is that Avago calls "AlGaAs"), maybe a few of the dimmer
ones have GaAsP instead.

- Don Klipstein ([email protected])

 

[Don Klipstein]

Yes, and that flicker apparently masks the 60Hz flicker from the
bulbs.


I can easily see fluorescent flicker if it's close.

If the ballast puts line frequency AC through the lamp, then the ends do
have 60 Hz flicker component. Electronic ballasts usually produce a small
amount of 60 Hz flicker - more if their filter capacitors are insufficient
or defective. I normally do not see 60 Hz flicker from fluorescents with
electronic ballasts, though I do usually see flicker from monitors set to
60 Hz.

- Don Klipstein ([email protected])

 

[krw]

Digi-Key has 8,884 items for discrete LEDs <75 mA, and 7,894 of them
are RoHS compliant.

(Actual number of different LEDs stocked is less - most come in at least
2 different forms of packaging, with separate catalog numbers.)


Nearly all red, orange, and yellow LEDs prior to the InGaAlP ones that
came out in the mid or maybe early 1990's have arsenic. One older red
chemistry, having peak wavelength 690, 697 or 700 nm and wide bandwidth,
does not.

Apparently includes:

Lumex SSL-LX20465YD (yellow)

Lumex SSL-LX20465ID (A slightly orangish red - known as "high efficiency
red" in the late 1970's and early 1980's).

At least 11 through-hole red Avago LEDs are currently in Digi-Key's online
catalog, and have wavelengths and brightnesses typical of GaAlAsP (or
whatever it is that Avago calls "AlGaAs"), maybe a few of the dimmer
ones have GaAsP instead.

- Don Klipstein ([email protected])

wwwWWWWOOOOOoosssssshhhhhh! (even after being given a clue, no less)

 

[krw]

If the ballast puts line frequency AC through the lamp, then the ends do
have 60 Hz flicker component. Electronic ballasts usually produce a small
amount of 60 Hz flicker - more if their filter capacitors are insufficient
or defective. I normally do not see 60 Hz flicker from fluorescents with
electronic ballasts, though I do usually see flicker from monitors set to
60 Hz.

I can see flicker from just about any fluorescent tube if the
lighting is just right (wrong?). It usually doesn't bother me too
much but I can see it. 60Hz CRT display flicker makes me physically
ill. I cannot have a display in my field of view set to 60Hz or I
will get ill.

 

[JosephKK]

I bought 1000 LEDs for the outside this year. Ick! What horrible
light. I've already bought incandescents to replace them for next
year. The LED strings go in the garbage as soon as the holidays
are over. A waste of $150, but sometimes education costs.

If you don't like them i will take them. May not use them for the
original purpose though.

 

[Don Klipstein]

So the tubes only conduct in one direction? They should have a 120
Hz flicker rate.

Most of the length of a fluorescent tube does do the same thing during
each half-cycle and flickers at 120 Hz. It's the ends that often have a
60 Hz flicker component. Each end usually produces a different amount of
light while being the cathode than it does while being the anode.

- Don Klipstein ([email protected])

 

[Don Klipstein]

I, Don Klipstein wrote in small part:Electronic ballasts usually produce a small

amount of 60 Hz flicker - more if their filter capacitors are insufficient
or defective. I normally do not see 60 Hz flicker from fluorescents with
electronic ballasts, though I do usually see flicker from monitors set to
60 Hz.

- Don Klipstein ([email protected])

Oops, brain fart - electronic ballasts normally have fullwave
rectification and whatever line-frequency-related flicker remains after
smoothing by the filter capacitor is 120 Hz.

- Don Klipstein ([email protected])

 

[neon]

In article <[email protected]>, To-Email-
[email protected] says...
> On Wed, 24 Dec 2008 19:55:24 -0600, "Tim Williams"
> <[email protected]> wrote:
>
> >80 LEDs (so far; I'm going to whip up another string of 40 yet), a PWM
> >driver (LM393) and an isolated switch running strings off the line.
> >
> >

> >
> >Tim
>
> Anyone made a synthetic candle flicker using LED's?
>
> I'm still using NE-2's, but I don't like the effect.
>
> What is stark contrast... my outdoor icicles are incandescent... my
> star-bursts are white-white LED's. I guess I need to go to all LED
> stuff ?:-(

I bought 1000 LEDs for the outside this year. Ick! What horrible
light. I've already bought incandescents to replace them for next
year. The LED strings go in the garbage as soon as the holidays
are over. A waste of $150, but sometimes education costs.

--
Keith

no you din't quit lying.

 

[JosephKK]

I can see flicker from just about any fluorescent tube if the
lighting is just right (wrong?). It usually doesn't bother me too
much but I can see it. 60Hz CRT display flicker makes me physically
ill. I cannot have a display in my field of view set to 60Hz or I
will get ill.

The only thing that ever bothered me is having a 72 Hz and a 75 Hz
monitor side by side. It also drove everyone that saw them running
together nuts.

 

[krw]

The only thing that ever bothered me is having a 72 Hz and a 75 Hz
monitor side by side. It also drove everyone that saw them running
together nuts.

That's weird. I have to set these two monitors to different
frequencies (75Hz & 85Hz the only choices above 60Hz) or I get
interference bars walking through the displays. Which raises the
question, how does one get interference bars on two monitors
running from the same display card? Seems to be a stupid design.

 

[Blarp]

That's weird. I have to set these two monitors to different
frequencies (75Hz & 85Hz the only choices above 60Hz) or I get
interference bars walking through the displays. Which raises the
question, how does one get interference bars on two monitors
running from the same display card? Seems to be a stupid design.

CRT's I presume?

Field coil magnetics interfere with each other. BTDT

 

[krw]

CRT's I presume?

Unfortunately, yes (new guy stuck with everyone's junk - 2GHz P4
processor too).

Field coil magnetics interfere with each other. BTDT

Sure, but why the different frequencies from the same graphics
card? I'd think it easier to use the same oscillator. If they
were the same frequency I'd likely never notice. In fact I don't
when they're set differently.

Actually, looking at it more closely, I do. I see it in the edges
(10Hz). Now I'm going to see it all the time (aack!).

 

[JosephKK]

That's weird. I have to set these two monitors to different
frequencies (75Hz & 85Hz the only choices above 60Hz) or I get
interference bars walking through the displays. Which raises the
question, how does one get interference bars on two monitors
running from the same display card? Seems to be a stupid design.

Your eyes generally try to smooth out the flicker. The beat
frequencies between two displays at different refresh rates causes
that mechanism to fail. Try forcing both monitors to the same
vertical rate.

 

[krw]

Your eyes generally try to smooth out the flicker. The beat
frequencies between two displays at different refresh rates causes
that mechanism to fail.

Duh! Ya think? The question is *WHY?*

Try forcing both monitors to the same vertical rate.

They are (when I can see the beat). That's the whole point. If the
monitors were driven by separate cards I could understand it.

 

[Greegor]

Why did he commit to 1000 before seeing a sample?

 

[krw]

Why did he commit to 1000 before seeing a sample?

No, I don't ask for engineering samples when I buy strings of
Christmas lights from Home Depot.