Handmade watch from the 90s



    Good evening harangers.
    Many were interested in my idea of ​​watches with vacuum fluorescent lamps.
    Today I will tell you how this watch was created.

    Indicators

    The main role is occupied by gas discharge indicators. I used the IV-6. This is a seven-segment luminescent indicator of the green color of the glow (In the photographs you will see a bluish tint of the glow, this distorts the color when photographing, due to the presence of ultraviolet rays). The IV-6 indicator is made in a glass flask with flexible leads. Indication is carried out through a lateral surface of a cylinder. The anodes of the device are made in the form of seven segments and a decimal point.
    You can apply the indicators IV-3A, IV-6, IV-8, IV-11, IV-12, or even IV-17 with a slight change in the circuit.

    First of all, I want to note where you can find the lamps that were produced in 1983.
    Mitinsky market. Many and different. In boxes and on boards. There is room for choice.
    It’s more difficult for other cities, maybe you’re lucky and you will find it in the local radio store. Such indicators are in many domestic calculators.
    Can be ordered from Ebay, Yes Yes, Russian indicators at auction. 1 2 3 4 On average 12 $ for 6 pieces.



    Control

    The AtTiny2313 microcontroller and the DS1307 real-time clock controls everything.
    The watch, in the absence of voltage, goes into power mode from the CR2032 battery (as on a PC motherboard).
    According to the manufacturer, in this mode they will work and will not fail for 10 years.
    The microcontroller is powered by an internal 8MHz oscillator. Do not forget to set fuse bit.
    Time setting is made with one button. Long retention, incrimination of hours, then minutes are incriminated. There are no difficulties with this.

    Drivers
    As keys on segments, I put KID65783AP. These are 8 "top" keys. I made a choice in the direction of this chip, just because I had it. This microcircuit is very common in the display boards of washing machines. Nothing prevents replacing it with an analog. Or pull the segments with 47KΩ resistors to + 50V, and push the popular ULN2003 to the ground. Just remember to invert the output to segments in the program.
    The indication is made dynamic, so the brutal transistor KT315 is added to each discharge.

    Printed circuit board

    The board is made by the LUT method , you can read about this technology from a friend DIHALT . The watch is made on two boards. How is this justified? I don’t even know, I just wanted to.

    Power Supply

    Initially, the transformer was at 50Hz. And it contained 4 secondary windings.
    1 winding - voltage on the grid. After the rectifier and capacitor, 50 volts. The larger it is, the brighter the segments will glow. But not more than 70 volts. A current of at least 20mA
    2 winding - to bias the grid potential. About 10-15 volts. The smaller it is, the brighter the indicators are, but the “not included” segments also begin to glow more strongly. The current is also 20mA.
    3 winding - to power the microcontroller. 7-10 volts. I = 50mA
    4 winding - Glow. For four IV-6 lamps, it is necessary to set a current of 200 mA, which is approximately 1.2 volts. For other lamps, the glow current is different, so keep this in mind.



    Later, I replaced the transformer with a pulse one. I recommend taking as a basis the power supply for halogen lamps, at the lowest power. It remains only to winding the windings to the desired voltage.
    Perhaps it turns out that for the glow of 1 turn is not enough, and 2 is a lot. Then we wind 2 turns and put in series a current-limiting resistor of 1-5 Ohms.

    Here is such an "electronic transformer" with an open lid.


    I can offer an option to make a power supply from a faulty energy-saving lamp. I described it here , to whom it became interesting - take a look.

    Firmware

    The firmware is written in C in the CodeVisionAvr environment.
    Who will undertake to repeat - write in a personal, I will send both .hex and the source.

    That's all.

    PS The material may contain spelling, punctuation, grammar and other types of errors, including semantic. The author will be grateful for the information about them ©

    UPD: Added the source github.com
    And the finished firmware

    UPD: At the request of adding a couple more photos.



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