Summary

I created home Halloween decorations and developed original LED candles.

Background and Purpose

Create the world's most realistic LED candles!

Due to safety concerns, LED candles that use LEDs to express flickering flames have become popular in recent years. They are used everywhere around us, from store displays to theme parks, stage productions, and even lanterns at festivals. However, many products repeat monotonous and short-cycle light-emitting patterns, and I wanted to challenge myself to see how realistic I could make it.

Development Process

Sketch

The LED candles developed will be embedded in Halloween decorations displayed in my home. At first, I drew some sketches to visualize the entire decoration image.

Policy

To express realistic flames with LEDs, the candle flame is divided into three parts: top, middle, and bottom, with one LED built into each part. Three LEDs are built-in per candle, and by controlling the light emission pattern of each part, a flickering effect similar to a real flame is expressed.

Generation of luminescence Data

The key to creating the most realistic LED candles would be to digitize the data from real candles and incorporate it into the artwork. Three light sensors were placed vertically to record the brightness of each part of the flame. Three sensors were fitted with covers to prevent each sensor from acquiring extra data on its surroundings. Analog data output from the light sensors was input to the analog port of the microcontroller to quantify the light levels. Based on the acquired data, scenarios for the output value (Pulse Width Modulation value) of each LED were created.

Each LED has the following characteristics in its issuance pattern.

• Top LED: This is the tip of the flame and flashes most intensely. This is the area most sensitive to wind. Voltage values are generally lower because of the thinner flame tip.

• Middle LED: This is the main part of the flame and has more light intensity than the top part. The output voltage value swing (difference between the minimum and maximum values) is large.

• Bottom LED: Since the bottom part is the root of the flame and the flame is always active, the voltage value does not drop to zero as in the top and middle parts. Therefore, the program did not control the light intensity, and the light was always emitted at a constant level.

Moreover, although candles are present inside and outside the jack-o'-lantern, the candles outside are more directly affected by the wind than the candles inside the pumpkin, so the degree of flame flashing should be more intense. Therefore, I decided to use different scenarios for the output voltage data of the LEDs to be used depending on the location of the candles. The two output data were created by adjusting the amplitude and bias of the measured data.

System Configuration

The system has LED control boards that control the top, middle, and bottom LEDs. Two sets of LED control boards are present for each candle in the jack-o'-lantern and the candles outside to change the light emission pattern.

Implementation

The pumpkins were purchased ready-made Halloween goods made with urethane. For the body of the candle, I used a PVC pipe purchased at a home improvement store and put a lot of effort into the wax dripping and the stain (aging) works in order to express realism and eeriness. The electronic board was made with stripboards. In addition, the control board and other components are enclosed in a waterproof plastic box to be used outdoors. The power is turned on and off using a household timer, and the system is designed to operate for a fixed time from sunset. After installation, the entire system was put into operation, and the lighting intensity and light emission patterns were fine-tuned to make the flames appear more realistic.

Luminescence of Developed LED Candles

Please compare real candles and my LED candles!

Real candles

Developed LED candles

Experience

Experience integrating the developed elements into a product and continuously operating outdoors for about a month.

Future tasks

To reproduce a more realistic flame, I would like to improve the system by incorporating a sensor that can detect the amount of airflow into each candle so that the degree of flickering of the flame changes in accordance with the amount of airflow each candle receives. The future challenge for implementation is to introduce printed circuit boards to reduce work processes and build a reliable system.

Gallery