VFD clock of Etienne | October 20, 2019 | VFD2 Tube Clock Project Comments
I present to you my finalized “VFD Clock” project.
Through this article, I will explain the electronic functioning of the clock and the VFD tubes that I used on it.
Good reading and see you soon to see the rest of my current projects
To start, here are some pictures of the set:
1] VFD IV-12 (ИВ-12) tubes:
The VFD (vacuum fluorescent display) tubes that I selected for this clock, are displays that were used in the 80s.
They have the particularity of being very resistant to cold. They were used in particular in the USSR.
It gives them a second life and I find them beautiful.
You can find them for purchase on ebay. Sellers are often found in Russia or Ukraine.
These displays consist of a heated cathode (filament), anodes and a grid. The whole is sealed in a glass envelope where there is a high vacuume.
Their operation is quite similar to a triode (with direct heating). The heated cathode allows the release of its electrons from its support.
The grid makes it possible to favor or restrict the passage of electrons, this in particular makes it possible to be able to make multiplexing.
When the grid and an anode are at positive potential, the electrons strike the fluorescent part of the controlled segment.
2] The electronic card
As mentioned in the previous article, I tested the services of the PCBWay site for manufacturing the PCB.
I had no problem except for the holes in the power connector but I realized that the GERBER was not very clear about it
So I did the drilling with my mini drill (dremel), as it is double-sided no problem to do so.
GERBER files are available at the end of the article.
Photos of the card before and after welding of the components
I made clocks a few years ago with a PCB made by myself.
I provide the files at the end of the article so that you can make it easier
This clock includes:
a PIC18 microcontroller
four VFD tubes
a VFD driver
a PWM LED driver
three power supplies
a backup battery
a light sensor
a temperature sensor
two operational amplifiers
four push buttons
2] Power supplies:
For this application, you must integrate:
a 5V power supply for the microcontroller, the RTC and the operational amplifiers.
1.5V 500mA power supply for VFD cathodes
a 30V 150mA power supply for the anodes and the grid of VFD tubes
The 5V supply is made by a linear regulator in a SOT89 box.
It is not easy to create a 1.5V power supply with an output current of 500mA. This current consumption is due to the power of the 4 cathodes (4 x 110mA max).
I chose to use the MC34063 circuit which is very suitable for doing this. It is configured in “step-down” mounting.
For the 30V power supply, I chose to use the same circuit. It can also be configured in “step-up” mounting.