Candle circuit needed...

[captainkirksdog]

Hello,
I need a circuit to simulate a candle with a very small incandescent lamp. I have tried using a 4011 NAND oscillator, as well as a 555. They worked, but not very well. A random or pseudorandom pulse oscillator would work, I think. How can I get one? Thanks.

 

[stevez]

I'd guess that you are looking to duplicate the apparent flicker of a candle. I'd start by using a simple photocell/amp hooked up to a scope to get a sense of the waveform that you need to generate. That might at least guide you in determining pulse length, frequency/interval and intensity.

I wonder if there wouldn't be a way to record the flicker with one of the voice recording ICs then play it back in a loop arrangment. Maybe a photocell could be connected to a VCO- record the resulting audio then play it back thru F/V convertor - with voltage that varies the lamp intensity. This is a bit more complicated though maybe not all that difficult. It would seem that it would result in the most real looking output though I don't know how important that is to you.

 

[Roff]

I'd guess that you are looking to duplicate the apparent flicker of a candle. I'd start by using a simple photocell/amp hooked up to a scope to get a sense of the waveform that you need to generate. That might at least guide you in determining pulse length, frequency/interval and intensity.

I wonder if there wouldn't be a way to record the flicker with one of the voice recording ICs then play it back in a loop arrangment. Maybe a photocell could be connected to a VCO- record the resulting audio then play it back thru F/V convertor - with voltage that varies the lamp intensity. This is a bit more complicated though maybe not all that difficult. It would seem that it would result in the most real looking output though I don't know how important that is to you.

Cool idea, Steve. I offer this enhancement only partially facetiously. It has a feedback loop to eliminate the nonlinearities of the light-to-resistance and voltage-to-light conversion processes that would otherwise be present. As you pointed out, an F/V and V/F (or PWM) converter could be in the record...playback block.

 

[zachtheterrible]

If you want to go really simple, ive seen light bulbs that simulate a candle. just screw one in and you're done :lol:

 

[Roff]

If you want to go really simple, ive seen light bulbs that simulate a candle. just screw one in and you're done :lol:

Jeez, Zach, you're takin' all the fun out of it! Why buy something when you can spend lots of time and money to come up with an inferior solution?

 

[zachtheterrible]

i was only trying to save captainkirksdog some time and money :cry:

 

[Oznog]

There was a kick-ass Atmel microcontroller circuit in Circuit Cellar about 2 yrs ago. They executed some complex mathematical modeling of a candle flicker and even included a self-heated, low thermal time constant thermistor which would cause it to flicker when blown on or if you were to walk briskly with it.

Amazing they were able to take something so simple and make it so complicated.

 

[audioguru]

Hi Ron,
You have a very low distortion lamp-flicker circuit. I used a similar idea to reduce distortion from an optical-FET circuit.

 

[Roff]

Hi Ron,
You have a very low distortion lamp-flicker circuit. I used a similar idea to reduce distortion from an optical-FET circuit.

Yeah, and God knows the world needs a very low distortion lamp-flicker circuit. :roll:

 

[audioguru]

Hi Ron,
There are probably some fanatics out there with their Monster Cable stereo speaker wire (oxegen free) and they drink only 1986 Bordeaux wine served at exactly 14.4 degrees C. They would appreciate the low distortion of your faux candle-flicker circuit.
It would be cool to make it so you could blow it out, without splattering wax all over the place. I've made discrete circuits with a differential input that drifts wildly if I warm one transistor with my finger. Self-heat them, then blow on one that is separated from the other and it could shut-down the lamp-flickering. You could even make it have spontanious combustion and smoke!
Everybody will want a few, right? Set-up production quickly, you're going to be a millionaire.

 

[Roff]

Hi Ron,
There are probably some fanatics out there with their Monster Cable stereo speaker wire (oxegen free) and they drink only 1986 Bordeaux wine served at exactly 14.4 degrees C. They would appreciate the low distortion of your faux candle-flicker circuit.
It would be cool to make it so you could blow it out, without splattering wax all over the place. I've made discrete circuits with a differential input that drifts wildly if I warm one transistor with my finger. Self-heat them, then blow on one that is separated from the other and it could shut-down the lamp-flickering. You could even make it have spontanious combustion and smoke!
Everybody will want a few, right? Set-up production quickly, you're going to be a millionaire.

Audioguru, I hope you're right - I just quit my day job. :wink:

 

[k7elp60]

Here is a circuit that uses LED's. D1 and D2 are flashing LED's, the same color. D3 and D4 are orange LED's. The circuit works equally well with just one orange LED.
I have built a few of these at Haloween time and put them in plastic pumpkins. They are surprizingly near a flickering candle.
What happens is the two flashing LED's get out of sync and the orange LED in series with them then flickers.

 

[captainkirksdog]

Thanks for the ideas, guys. However, the operative words were "very small incandescent lamp". These are the kind used in miniature railroads or dollhouses. The ones I'm using are about 1/4" long. Just a bit bigger than "grain of wheat" bulbs.

 

[Roff]

Thanks for the ideas, guys. However, the operative words were "very small incandescent lamp". These are the kind used in miniature railroads or dollhouses. The ones I'm using are about 1/4" long. Just a bit bigger than "grain of wheat" bulbs.

Have you chosen a bulb? If so, what is the part number, and/or what is the voltage and current rating?

 

[k7elp60]

captainkirksdog,
I took my circuit and replaced the orange LED with the diode input of an opto-coupler and a resistor in series. The transistor output of the optocoupler I used to control a incandescent 12 volt bulb. I could control the intensity of the bulb by varying the applied voltage. The bulb seemed to flicker like a candle.
If you can give me the voltage a current rating of the bulb you want to use I will redraw the schematic with my recommendations as to parts and values for the components.