The Christmas LED-Snowflate-thermometer

Новогодняя светодиодная снежинка с микроконтроллерным управлением и индикацией температуры

This LED "Snowflate" made from mainly blue and white LEDs and can serve as Christmas present, Christmas ornament or night light. The device also has a thermometer. Snowflake has 6 beams and every beam contains 8 superbright LEDs. I have used blue and white LEDs with different diameters. Their location is shown in the figure

Leds layout

The assembled snowflake looks as follows:

LED Snowflake

The circuit of the device is shown in the figure below. 48 LEDs and 7-segment indicators are connected to the pins of the microcontroller ATMega8535.

Led snowflake circuit

LEDs are divided into 6 "beams" (common-anode) to 8 pieces each. LED cathodes are connected to pins HK1 - HK8, and anodes - to pins HA1 - HA6. Cathodes and anodes of a three-digit seven-segment LED (with common anode) are connected to pins LK1 - LK8 and LA1 - LA3 respectively. Transistors VT1 - power transistors with VT8 - npn (!). I used KT815. I haven't found npn transistors in an appropriated package in the Eagle library and used pnp transistors on the circuit.

As themperature sensor I have used IC3 DS18B20, the button S1 is reserved and doesn't used by current version of firmware. The UART-s pin and pin PD4 used for the bootloader. I have used the crystal resonator with frequency 11.0592 MHz.

Assembled device:

Snownflake PCB

Video demonstration


DownloadFirmware (11.0592 MHz)
DownloadSource code
DownloadCircuit adn PCB, Eagle
DownloadLED board, SprintLayout

DownloadAll in single file

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