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Yellow 5050 LED - awesome for any candle project

There are many candles of shame scattered around our house - early experiments with multiple LEDs (types and colours) in an attempt to produce the elusive Holy Grail of a lifelike flame emanating from an electronic device. 

In the quest for authentic fakery I firstly tried different colour combinations of orange, red, yellow and warm white searching for a good flame effect. Early recipients of these efforts (sorry...) were sometimes honest in their appraisal and I thank them for their feedback. I suspect a few of those "candles" are carefully filed in truncated inverted conical open ended filing cabinets now.

I tried 3mm, 5mm and various SMD LED formats from different suppliers as part of the experiment. I covered various LED combinations in hot glue, half table tennis balls, grease proof oven paper, tissues, and anything else diffusive that I could find around the house. They're all good in their own way, but ultimately none really were candle-like for various reasons.

All those failures helped focus the requirements for the source of light at the same time I was fiddling with the code looking for acceptable "randomness" to drive the flame.

Early prototype - "white" flame from hot glue

Then one day in 2018 I was skiing virtually through the LED valleys on the internet when I came across a 5050 format LED which seemed to have three pins in and out - surely not! Three LEDs in one - that's heaven for someone looking for a compact controllable efficient package.

I ordered red, orange, yellow, warm white and cold white versions and then sat by the post box in anticipation. All the colours were interesting, but the yellow version was oh so lovely as a candle, and all recent recipients have reported a pleasing realistic candle-like glow emanating from the devices.

The candle project at the time (and still now) has two independently ramping PWM channels, one of which supplies a randomly varying "slow" steady up and down ramp and the other a randomly varying "fast" flickering ramp which gives a little more "life" to the "flame".

The slow ramp signal outputs to two of the LEDs in the package and the fast ramp to the remaining LED. Daredevils could reverse this for a more intense flame. There were some other "breakthroughs" after discovering this LED package. A friend mentioned that the hot glue flame was a bit woeful so I bought some little uniformly round fresnel lenses to help diffuse the glow.

Also I started to put the LED combo on the inside of a glass jar (they used to be hilariously stuck on the outside) and with the inside of the glass jar sprayed with a bit of diffusive white paint, the result was a warm diffuse candle-like ambience. It also helps if the jars are contoured to refract the light more realistically.

Whether the candle is powered by an old battery or rechargeable via a solar panel is irrelevant to the flame quality - but I definitely prefer the solar version for ease of use and sustainability.