Ceramic Filament Clock 1.0

Hardware
      circuit part: Main control circuit module, digital tube module and digital tube connection base. The main control circuit is the 51 single-chip microcomputer control part, which includes the 51 single-chip microcomputer minimum system, clock control and digital tube control circuit. The digital tube module display lamp uses ceramic filaments, so this project is called "ceramic filament clock".
      Other parts: battery, clock circuit backup battery, lithium battery charging module and power switch.
PCB part The
      digital tube display part is composed of two two-digit digital tubes and a stopwatch display. The digital tube is connected to the main control circuit by another PCB board.
      There is a digital tube position selection circuit in the connection board, where 1 and 3 are connected to the first digital tube, and 2 and 4 are connected to the second digital tube. When the four-digit clock is displayed, because the two connection boards are connected on both sides of the main circuit board, the position selection can be 12 or 34. Only when the eight-digit clock display is made, the two connection boards need to be connected together, and it is necessary to distinguish.
      When selecting the position, you can connect directly, or you can weld resistors or adjustable resistors. Because there is no automatic brightness adjustment function, after many verifications, I welded a 270 ohm resistor here (I personally think this brightness is just right for me), you can set it according to your needs.
      When the four-digit display is used, the seconds do not need to display the seconds, only the two in the middle need to flash. As shown in the figure below, the control end of the seconds display close to G can be directly connected to G, and the side close to 1 is the common end of the seconds display, which needs to be connected to an unoccupied 1 in 1234 at the board connection. This is the same as the digital tube position selection, but leads are required. There
        is also a small piece of download circuit in the PCB file, but because I have no time recently, this circuit has not been empirically tested. You can ignore or remove it. If you have time, you can help test it. Also, if the PCB proofing cannot be done for free and the cost of digging the slot is required, you can take out the middle control circuit, connection circuit and download circuit and reassemble them. There are two places
in the program part
       that need to be modified, and the others can be left unchanged unless it is an eight-digit display. One place is the selection of the digital tube display position, and the other place is the time setting.
       The digital tube position selection is determined according to the digital tube position selection of the hardware circuit connection board. Here you can directly download the "digital tube position display" program and enter it to display it directly, as shown in the figure below. Then change the uchar SZ1=2, SZ2=3, FZ1=4, FZ2=5, MZ=1 in the main program according to the displayed number, as shown in the figure below. Because the seconds display does not display numbers, you need to find it manually. You can change the value of MZ=1 and download it to see if the seconds flash.
        The program for setting the time DS1302_SetTime(); This line of code is to write the time program. There are two situations where this line of code needs to be written. One situation is that there is no time program in the DS1302 chip, and the second situation is that the code in the DS1302 chip is disordered, such as power failure and restart without a backup battery. Therefore, after writing the time program, you need to comment out this line of code and write the code again to lock the time, otherwise the time will be written again when resetting or power failure and restarting, and the time retention function cannot be realized.
The shell part
        The shell is 3D printed and is divided into a shell and a base. The base and the shell are fixed with injection molded copper nuts (2*3.5*2) and screws (M2.5). Another thing to note is that when installing the power switch, you need to use hot melt glue to fix it.
The effect demonstration
       cannot be uploaded here because of the video size. If you need to watch related videos or tutorials, you can go to the B station with the same name (mechanical and electrical novice) and search for it on the homepage to see it.
      Video link: Ceramic filament clock, 51 single-chip microcomputer control version. _哔哩哔哩_bilibili
Change log
      May 14, 2023 Added a program to set the brightness to dim at night. May 14
      , 2023 Added a new model of the shell base. The screw hole position seems to be a little different in the previous upload. Corrected and updated. May 14
      , 2023 Added the component material list of the PCB board.
      May 30, 2023 Added the total bill of materials.
      June 22, 2023 Added the program for the PCB board to display the reverse
      June 22, 2023 Added the burning software file.