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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