#The7thLiChuangElectricityContest# Nixie tube watch

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* 1. Project Function Introduction
This is a Nixie tube watch that uses B5870 Nixie tube as a display device, with the advantages of low power consumption, wireless charging, Bluetooth timing, etc.
 
*2. Project attributes
original
 
* 3. Open source agreement
CC-BY-NC-SA 3.0,
 
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hardware demonstration video! As a wearable device, the main control chip has extremely important power consumption and battery life. The main control chip model is STM32L051, which has excellent low power consumption performance and is very suitable for this project scenario. The microcontroller is usually in a dormant state, and it works after being awakened by the accelerometer interrupt signal to drive the Nixie tube display circuit, etc. Accelerometer The accelerometer model is LIS2DW12, which also has excellent low power consumption and low noise performance. More importantly, it has a data processor, which can easily realize functions such as motion detection and wrist lift detection by configuring relevant registers. I will put the accelerometer processing code in the attachment area of ​​the open source platform, and everyone is welcome to communicate together. Wireless charging circuit For wireless charging, I use the BQ51050 chip, which is compatible with the WPC v1.2 Qi industry standard, suitable for most wireless charging stations on the market, and can directly charge lithium batteries. Note that the chip peripheral circuit must be consistent with the circuit recommended in the data sheet to avoid charging failure. Clock chip The clock chip I use is DS3231, which is relatively stable and can be used for several years without time calibration. The boost circuit requires a high voltage of 170V to drive the Nixie tube. I use a classic flyback boost circuit here. Be very careful when welding and debugging, and be careful that high voltage electricity will damage low-voltage circuits such as microcontrollers. Pay attention to isolation in circuit layout, avoid accelerometers, Bluetooth modules, microcontrollers and other devices: Nixie tube drive circuit I use HV5523 to drive Nixie tubes, which is a 32-bit serial data to parallel data chip with open-drain output, and the output voltage is as high as 230V, which is very suitable as a chip to drive Nixie tubes: Other circuits There is a BT24 ultra-small Bluetooth module in the circuit for Bluetooth timing; a Hall sensor for sensing magnets for interaction; other circuits are not described in detail, please refer to the EDA schematic diagram for details. Nixie tube selection In order to make the watch as small as possible, I chose the Nixie tube model B5870 (about 13mm in diameter): Of course, you can also use Nixie tubes of similar size such as B5750 instead. Shell The shell is designed by myself, and the model is placed in the accessory area. At present, nylon 3D printed parts are used, and CNC processing shells will be used if conditions permit: the shell has a buckle, which can be perfectly combined with the PCB, and the watch mirror is 40mm in diameter and 1mm thick; the back cover of the watch can be made of PCB or carbon fiber board (metal cannot be used to prevent interference with wireless charging). With waterproof rubber ring design, it can prevent water splashing in daily life. The picture shows the actual PCB picture: Other precautions If you want to replicate this project, you must have sufficient knowledge of hardware circuits and be careful of high voltage dangers! ! ! Burning is carried out through an 8P FPC seat: After connecting the battery (451225 is recommended), the DS3231 clock chip will work; the switch in the figure below is used to turn off other components except DS3231 (the Nixie tube boost circuit is still powered but cannot be enabled, so it cannot boost), and the high voltage can be turned off with one button to ensure debugging safety. *5. Software part I will put the driver code of the accelerometer LIS2DW12 and the code of the HV5523 driving the Nixie tube in the attachment area: