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  • Electronic LED Candle

  • Created: Mar 16, 2016

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This reference design is a simple electronic LED candle that is well suited for birthday occasion. It acts like a real candle, which constantly flickers and changes its light intensity depending on the airflow. It has 9 LEDs, which blinks at random period and phase that can also be blown by the user as if it is a real candle. It specially uses the C&K’s PTS830GM140 tactile switch, a micro-miniature switch with low profile and high actuation forces designed for wearable electronics. It features extremely low start-up voltage and high output voltage accuracy.

The heart of the circuit is the Atmel ATTINY44 microcontroller that has a built-in differential ADC channel with 20x gain connected to a piezo sensor. The sensor and a special air trap help detect airflow with astounding sensitivity using resonance effect. In addition, a step up dc-to-dc converter with SOT-23.5 package and additional chip enabled input is used to increase the output voltage to 3.3V. This also helps turns off the converter with ultra-low supply current.

Electronic LED candle basically flickers when it is not yet blown or no airflow detected. LEDs are switching (on/off) during piezo sensor sampling phase, which brings additional noise. An increase of intensity of the airflow would cause the LEDs to turn off at a certain time, which makes it a perfect alternative for candles since it does not melt wax that may scatter on top of the cake. This circuit may also be modified as desired by the user that may suit at any occasion.



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