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Artificial candle is ‘ignited’ by a real flame
This 3D-printed artificial candle is
not turned on using a switch; instead,
it is ignited using the flame of a real
matchstick or lighter, just like an ordinary candle. When a flame is brought
near the tip of the artificial candle, the
LED bulbs magically light up. They
also flicker like a real candle.
The trick here is simple: a hidden
flame sensor is installed at the top of
the candle. This signals an Arduino
Nano board inside the candle to turn
on the LEDs.
It uses two yellow LEDs and one red
LED to produce the flickering effect.
They are switched off in a pattern, one
after another, to create the flickering
effect. These features make our artificial candle look almost real.
It is powered by a small 3V coin
cell for portability. I've also added a
small slide switch at the bottom of the
candle to switch it off. The plan is to
eliminate this in a future version of
this project where you can blow on it
to turn it off! But until then, it has to
be manually switched off.
Note that a few slightly different IR
flame sensor modules are available,
but they all work similarly. If using
another type, check the pinout and
adjust the wiring as necessary.
The body of the candle is 3D printed.
I designed the model in Tinkercad. It
siliconchip.com.au
comprises four main pieces: the cylinder, base, top and flame cover. The
main cylinder is hollow, and it houses
all the electronics. The top and bottom pieces are designed to be a snapfit onto the main cylinder.
The bottom piece has a small rectangular opening for the USB port of the
Arduino Nano board. There are four
small holes in the top part: three for
the LEDs and one for the flame sensor's IR diode.
The flame cover acts as a cap and
diffuses the light from the three LEDs.
It needs to be printed in white plastic,
and it has very thin walls so that it is
translucent. You can download all the
3D printing files from www.tinkercad.
com/things/4iuOdy6Wpmp
After printing these pieces, insert
the LEDs in the central holes in the
top piece in no particular order. Also
insert the flame sensor's IR diode halfway through the remaining outer hole,
then fix the module to the underside
using hot melt glue, silicone or another
adhesive.
You can now connect the wires from
the LEDs and the flame sensor to the
Arduino Nano board, then wire up
the button cell via the slide switch.
Insert the circuitry into the candle
body, then push the top piece onto
the main cylinder.
Australia's electronics magazine
The bottom piece has a small rectangular opening to accommodate the
small slider of our mini DPDT power
switch. Insert the slide switch from
the inside of the bottom part, aligning
it such that the slider can properly be
moved from the outside, then fix it in
place using hot glue/silicone etc. Once
that’s solid, push the bottom piece into
the main cylinder.
Add the flame cover to the top, and
the candle is ready for programming.
The Arduino sketch required is relatively short, but we don’t have space
for it here, so download the file “Artificial candle.ino” from siliconchip.com.
au/Shop/6/6478
Fire up the Arduino IDE, open this
file, select the Nano board from the
menu and set up your COM port, then
choose Upload. Check that you get a
success message in the window at the
bottom of the IDE.
Ensure the slide switch is on, then
bring a flame near the top of the candle and check that it switches on and
then flickers. When finished, switch
off the slide switch in the base.
You can use the same principle to
light up any other shaped lamp. You
could also use different coloured LEDs
in the candle to get different effects.
Aarav Garg,
Hyderabad, India. ($120)
June 2022 89
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