Piddling around with more LEDs

[Tim Williams]

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

 

[neon]

use a triac direct from the line how many on a string? use a diode and a big cap 84 LED . not only that no PWM just direct from my HI-FI output beat that if you can? want to know more?

 

[Tim Williams]

Anyone made a synthetic candle flicker using LED's?

Usually done by blending together (AND, OR, XOR?) three squarewave
oscillators running at different frequencies. I don't like the results
though. Is there a strong source of slow (1/f) noise? Maybe FET CCS
amplified a bunch?

Ironically, this controller flickers pretty well at low bias. I'm guessing
ambient noise is enough to push it just over threshold, since there is some
hysteresis between "fully off" and "lowest duty cycle". It doesn't hurt
that vision is logarithmic so you can clearly see microamperes in the damn
LEDs (I can't probe the switch's drain waveform without the LEDs glowing a
little, and it's a 10M probe). I haven't decided yet if it's noise in the
"differential" amplifier (= two transistors and two resistors, bad CMRR,
etc.), jitter in the PWM comparator, line noise or what.

Tim

 

[krw]

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.

 

[krw]

I don't know. I sort of like the white-white look.

These are bluish-white and the flicker is horrible. They're built
like crap too, but that's another issue.

 

[Tim Williams]

Mine are white-white... no flicker. You must have bought cheap shit
;-)

Easy to "rectify" anyway... cut off the ends and have at it.

Tim

 

[krw]

Mine are white-white...

They're called "cool white", but they're sickly blue.

no flicker.

60Hz. Many can't see 60Hz flicker (evidenced by their monitor
setups). I can.

You must have bought cheap shit
;-)

Cheap? No, over 10x the price of incandescents ($36/200).
Shit? Absolutely.

 

[Ken]

They're called "cool white", but they're sickly blue.


60Hz. Many can't see 60Hz flicker (evidenced by their monitor
setups). I can.

I can see 85Hz flicker.

 

[Adrian C]

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.

How many LED's do I need to collect to be in possesion of a worrying
amount of Arsenic?

 

[Don Klipstein]

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.

Usually, candles flicker because of turbulence. In most candle flames,
the turbulence is a low order one and approximates a single frequency
continuous oscillation, at maybe 6 Hz or so.

I would think that putting random noise through a narrowband and
highly resonant (which go together to some extent or another) 6 Hz
bandpass filter, and have the output of that mixed with DC to power an LED
of suitable color. (A candle flame has color and spectrum close enough to
that of a 1900 K blackbody, maybe 1850 K for somewhat larger and more
flickery flames.)

- Don Klipstein ([email protected])

 

[Don Klipstein]

These are bluish-white and the flicker is horrible. They're built
like crap too, but that's another issue.

I often like the bluish white light, though I expect to get tired of
it if too many lights end up having that color. I hate it when too
many holiday lights are of one particular color. And I have seen some
nice ones at Target a year ago about the color of carbon arcs.

As for the flicker - plenty lack fullwave rectification and so they have
60 Hz flicker. I find that a little noticeable and a little irritating.

I have seen some with better rectification - try to test them or see a
sample plugged in at the store.

- Don Klipstein ([email protected])

 

[krw]

I often like the bluish white light, though I expect to get tired of
it if too many lights end up having that color. I hate it when too
many holiday lights are of one particular color. And I have seen some
nice ones at Target a year ago about the color of carbon arcs.

As for the flicker - plenty lack fullwave rectification and so they have
60 Hz flicker. I find that a little noticeable and a little irritating.

I have seen some with better rectification - try to test them or see a
sample plugged in at the store.

The fluorescent lighting in the store doesn't help. However,
switching back to incandescents is guaranteed to eliminate the
problem.

 

[Adrian C]

How many do you eat, each day?

LED poisoning, ugh...

</flump.....>

 

[Jasen Betts]

Yes, tha tseems like a good explanation.
Still it would be cool if yo uwalked past theLED candle,
that like wit ha real cande the falme flickers some because of the air
flow past it from your motion.
So i was looking for a real low thermal mass sensor (very small NTC,or even diode,
hanging from very thin wire to give thermal isolation, with a slight bias current
to keep it warm:

exposed lamp filament? (but it's PTC not NTC)

 

[Tim Williams]

If they are Chinese LEDs, it would be lead LED poisoning.

If they're not RoHS, it would be lead lead LED poisoning.

Tim

 

[krw]

If they're not RoHS, it would be lead lead LED poisoning.

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

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

 

[Don Klipstein]

The fluorescent lighting in the store doesn't help.

That has flicker in USA having fundamental frequency 120 Hz.

Those with vision sensing flicker at frequency that high on/near Earth's
surface tend to be insects, aliens or other things than
anywhere-near-typical human beings.

However, switching back to incandescents is guaranteed to eliminate the
problem.

I suspect very strongly that for close to 99% of humans, something more
energy-efficient than that and economical is now available.

 

[Michael]

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

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

Many, many of the LEDs in DigiKey catalog are marked "RoHS Compliant"

 

[krw]

That has flicker in USA having fundamental frequency 120 Hz.

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

Those with vision sensing flicker at frequency that high on/near Earth's
surface tend to be insects, aliens or other things than
anywhere-near-typical human beings.

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

I suspect very strongly that for close to 99% of humans, something more
energy-efficient than that and economical is now available.

No thanks. Burned once. $150 down a rat hole is several years
worth of electricity for the incandescent replacements.
Incandescents are an order of magnitude cheaper than new LEDs, so no
savings to be had there either.

 

[MooseFET]

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


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

The frequency response of my fovea is not as fast as the rest of my
eye. I don't see the flicker when I look directly at the tube. With
just one tube, I can see it in the lighting of the room. Most two
tube ballasts do a good job of putting about a 90 degree phase shift
on the current to the two tubes so I only notice the flicker when one
tube is out.

The new "high efficiency" lights, that use the thin tubes don't make
as much flicker. They just fail and burn out their tubes, flicker and
flash in their own funny rhythm and draw a lot more current than the
old ballasts did.