Piddling around with more LEDs

Northern Tools is selling an aluminum flashlight with 95 white LEDS for $19.95 right now. I bought one for my emergency kit.

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There are two kinds of people on this earth: The crazy, and the insane. The first sign of insanity is denying that you're crazy.

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 ?:-(

...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

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

On a sunny day (Thu, 25 Dec 2008 01:07:31 -0600) it happened "Tim Williams" wrote in :

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.

A friend of mine used a CMOS op-amp configured to have a very high gain, amplifying the noise of its own input stage. I don't know the details, but I remember that he was happy with it. It is probably necessary to roll the gain off at really low frequencies (? 0.01Hz) so that DC offset does not rail the opamp.

Chris

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.

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

...Jim Thompson

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

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

...Jim Thompson

"Jim Thompson" wrote in message news: snipped-for-privacy@4ax.com...

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

Tim

Offer them on Freecycle. If people will take dead TV sets, they'll take flickering lights. That, or stick them in the guest room so company doesn't stay very long. ;-)

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

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

I can see 85Hz flicker.

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

How many do you eat, each day?

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 ( snipped-for-privacy@misty.com)

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

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

- Don Klipstein ( snipped-for-privacy@misty.com)

On a sunny day (Fri, 26 Dec 2008 03:56:38 +0000 (UTC)) it happened snipped-for-privacy@manx.misty.com (Don Klipstein) wrote in :

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: + | resistor AC coupling |-------------||----- opamp x 1000 -------- NTC | ///

So, only amplify AC, the fluctuations, and superimpose that on the LED DC current. And then combine it with your idea.

On a sunny day (Thu, 25 Dec 2008 22:36:14 -0500) it happened "Stephen D. Barnes" wrote in :

Ah, the PIC to the rescue :-)