Re: Advice for X-mass light flicker?

The 7555 is actually quite good for this with very low current draw and long time constants. Addition of one diode across Rb (pins 6-7) in the right direction will allow roughly constant period and a variable duty cycle. He can even use a three legged rheostat in this circuit ;-)

If you want something better then use two - one as an astable to set the frequency and then trigger a monostable to alter the duty cycle.

Regards, Martin Brown

Joey Faye would be proud of you...as would Abbott and Costello

mike

Step by step...

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Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

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Politicians should only get paid if the budget is balanced, and there is
enough left over to pay them.

I only bothered getting this thread because I thought it was something to do with some sort of mass spectrometry I hadn't heard of.

Pity the OP (whoever it was) can't spell "Xmas".

And didn't post it in s.e.basics.

:-(

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

On a sunny day (Thu, 11 Nov 2010 12:11:41 -0800) it happened Fred Abse wrote in :

BASICS? It is very difficult to make a light flash absolutely random :-)

Fred Abse wrote in news: snipped-for-privacy@invalid.invalid:

Well it is a design attempt. Simple though it may be ,and this is sed. Considering 99% of the stuff posted here has nothing to do with electronics design or otherwise you may want to take your criticism to any of the other numerous OT posts that are far more deserving of it.

If you think its so trivial then offer a suggestion or if you cant say something nice then STFU.

snipped-for-privacy@invalid.invalid:

When you are ready to go digital, it would be a no-brainer with the m...

You're not turning your control element fully off during "off" time.

Do you have a schematic you could post either to alt.binaries.schematics.electronic or to some webpage? (Tripod, some image drop somewhere, your ISP's "personal web space", whatever?)

Sure it can. Use one resistor for charge, and another for discharge, and distinguish which is which with diodes. ;-)

Have Fun! Rich

Maybe something like this would help:

It slowly dims and brightens the lights at some rate set by the 100K pot.

The top 2 op-amps generate a low frequency triangle wave which is compared to another faster running triangle. The output at pin 14 is a

0 to 100% or more varying duty cycle used to drive the transistors and lamps. It's drawn to fade one set of lamps while brightening the other.

You could possibly gate the signal at pin 14 with a 555 of some duty cycle to switch the lights on and off at various rates and brightness levels. Should give a flicker effect adjustable with 2 pots. Probably not random, but might have interesting patterns.

-Bill

Google "LED candle", "Electronic candle" or variations on these. These use a small PIC with a quasi-random flicker generator. No Triacs needed.

How many lamp groups will you be flickering? The 555/Triac per group is going to get pretty hairy whereas the PIC will only need one output pin (and maybe a transistor) for each group. And the PIC algorithm will produce a much more random flicker effect than a 555 will.

I don't know if anyone makes an LED with an integral flicker circuit, but I suspect that since LED candles are quite popular, there may be some out there. That would solve practically all of your problems.

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

I don't actually object to OT posts.

My point was that had the thread been titled using "Xmas", instead of "X-mass", it would just have been ignored.

I didn't see the OP, anyway, since it was Google.

--
"For a successful technology, reality must take precedence 
over public relations, for nature cannot be fooled."
                                       (Richard Feynman)

Isn't X-mass when Mulder and Scully go to church? ;-P

Cheers! Rich