Flameless Candles

Uh -- a little bitty circuit board, with a bunch of traces going into a little black lump, some resistors, maybe a transistor and an LED.

I don't know if there's an easy analog way to do it, but it'd be a snap with any little microcontroller that has a timer, and not too hard without: generate a random number, filter it a bit, drive about that hard, repeat.

I can't think offhand how to do that analogly, although if it's done that way it's probably an intentionally chaotic circuit.

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Tim Wescott
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Do you need to implement control loops in software?
"Applied Control Theory for Embedded Systems" was written for you.
See details at http://www.wescottdesign.com/actfes/actfes.html

Surfing around it seems to be randomly addressed LED's, BUT with fade-in/fade-out.

I'll have to experiment... I like luminarias ;-) ...Jim Thompson

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| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
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If Nancy Pelosi gave Obama one of her balls, they'd both have two.

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

This work for you?

Random noise generator followed by a resonant fairly narrowband bandpass filter with center frequency around 5 Hz or so. Amplify, mix with DC if the noise is not already a noisy DC voltage.

If the noise is white rather than closer to brown, a peaky resonant lowpass filter such as a Sallen Key lowpass one will probably do the job.

Use the noisy DC to power a "warm white" LED. Sand it or surround it with diffuser material, probably also surround it with a "full CTO" ("color temperature orange") filter. White LEDs will probably have close to accurate candle flame color with 2 "full CTO" filters. You can experiment with filtering - CTO comes in degrees of orangeness besides "full". Some "warm white" LEDs may need more than one unit of CTO filtering to get a nice warm flamy color. There are CTS (color temperature "straw") filters, in case you want the color slightly more yellowish and less pinkish. These filters are available from theater supply shops, in 20 by 24 inch sheets at very reasonable prices, and big long rolls if you really want a lot of filter "gel" material.

I just tried filtering a "warm white" LED - I think "full CTS" does a pretty good job. If you have a really warm one, 3/4 CTS or 3/4 CTO may do better.

I have a few of those sample booklets of filter gels available for free from many theater supply shops.

--
 - Don Klipstein (don@misty.com)

These won't do?

Maybe something like this? (assuming there's a split supply created for the opamps)

VCC VCC VCC + + + | | | .-. || | | | | -------||----------. V -> | | | | || | - | '-' || |\ | | | | '-------||------|+\ ___ | ___ |\ | | | | || | | >--.-|___|-'|___|---o----|-\ | |/ \| ---o--| |--- |--- | | |/ | | .-|+/ .'. |>

Sorry, I messed up the Sallen-Key topology in the schematic above - switch the inputs and take Vout back to the negative input of course :(

Use a pseudo-random generator, OR a few register output bits to a driver.

"Jim Thompson" kirjoitti viestissä: snipped-for-privacy@4ax.com...

Some net sources say that things like that use music IC for random-looking flicker.

How about a really noisy zener as the voltage reference that sets the average LED current. Filter the noise to get a 'nice' flicker.

George H.

There are cheap Chinese 'tea light' LED candles available at a few arts and crafts stores. Michaels is one that comes to mind

You could mold wax around one of these (leaving the base of the candle exposed for battery access and switch operation).

I can't remember the price, but I think its less than $10 per.

The one down side to many of these is that they take little button cells. Necessary for the small form factor but expensive if you've got the real estate to use a couple of AAA cells.

--
Paul Hovnanian  paul@hovnanian.com
----------------------------------------------------------------------
Have gnu, will travel.

Watching them, it's strictly amplitude variation. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

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

Most have 2 or 3 LED's and they try to mimic the flame dancing around. A fairly chaotic and not so chaotic set of events.

I vaguely remember some bulbs that used to emulate them well, but they have been discontinued. The awful flicker bulbs are still made.

The café in town has charming gas lamps, these are very hard to duplicate.

There would be a market for a good substitute.

Cheers

"Jim Thompson" schreef in bericht news: snipped-for-privacy@4ax.com...

The first one I got my hands on, played a tune. I could hear it using a simple crystal earphone. The second one only made some meaningless noise. When watched on the o'scope however I saw only some kind of binary data on both of them. So I guess some kind of PWM for the tune, some kind of other pseudo random generator in the other. They were powered by a button type, 3V lithium battery. Both were dirt cheap, less then an euro a piece. The pseudo random string was not very long so you recognised the pattern looking at them for some time.

If I wanted to make something similar, I'd go for a PIC10F200, a capacitor, a LED and a 3V battery. Maybe two 1.5V batteries. The only challenge is to find an algoritm that makes and authentic flicker with long enough a sequence.

petrus bitbyter

The old house had natural gas, so we had a gas lamp out front, by the rural mail box ;-)

No gas available here, except tanked-in propane :-(

But a whole lot less house fires. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

[snip]

I'm pondering an LM3914 driven by the sum of 1Hz, 3Hz, and 5Hz. ...Jim Thompson

--
| James E.Thompson, CTO                            |    mens     |
| Analog Innovations, Inc.                         |     et      |
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    |
| Phoenix, Arizona  85048    Skype: Contacts Only  |             |
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  |
| E-mail Icon at http://www.analog-innovations.com |    1962     |
             
I love to cook with wine.     Sometimes I even put it in the food.

I'd think that a combination of several linear-feedback shift registers, of different periods (maybe three hooked up as an alternating-stop-and-go generator) would have a long enough period,

Run three sets in parallel, take the three bits for each iteration and treat it as an integer between 0 and 7 (or 1 and 8) and use this to set the PWM control register in the PIC and drive an LED (many PICs can sink enough current to light up an LED directly).

--
Dave Platt                                    AE6EO
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LFSRs with differing lengths might work.

That, or just use three pins on the uC with appropriately weighted resistors (not necessarily binary).

Disneyland has been using incandescent lamps that flicker like oil lamps for a long time. The circuit can't be too complicated. Of course, their pseudorandom generator could be a set of lumpy conductive disks cranked by an appliance timer motor.

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