After I completed the filament driver and the circuit to drive the multiplexed VFD segments, it is time to finish the VFD clock project I had in mind earlier.

On the circuit side, there isn’t too much to it. All I needed was a realtime clock and a microcontroller to interface with the RTC and the VFD driving circuit I discussed before. The RTC chip I used is a high accuracy DS3232 from Maxim. A more popular RTC chip such as DS1307 can also be used here without too much programming change. The microcontroller I used is an Arduino bootloaded ATmega328P. Since the VFD driver circuitry requires a higher DC voltage (e.g. 27V, a few milliamps) for the anode plates and gates but the TTL circuit only needs 5V, the power supply must be able to provide both required voltages.

My original plan was to use a 20V transformer and then use the rectified and filtered DC output to drive the VFD plates/gates and then use a switching DC-DC converter chip to provide the 5V required by the rest of the circuit. But my order was delayed so I decided to go with a 7805 linear regulator I had on hand instead. Even though the current requirement for the 5V rail is low (at only around 150mA), the power dissipation for the 7805 is quite significant due to large differential between the input voltage and the output voltage. I had to use a rather beefy heat sink to keep the temperature under control (see picture below). Once my order arrives, I plan to replace this linear regulator with a switching regulator.

VFD Clock
VFD Clock

Here is a short video showing the basic functionality of this VFD clock I built. You can download the code towards the end.

View on YouTube in a new window

Download source code: VFDClock.tar.gz

Be Sociable, Share!

5 Thoughts on “VFD Clock – Putting Everything Together”

  • Nice! But that heat sink is pretty big: why don’t you just use a DC-DC step up converter to produce the 27V for the VFD? That way, you can power the whole thing from e.g. 7.5V (and get rid of the transformer, although you’ll need a switch mode power supply wall wart, which are cheap), and use your 7805 without heat sink to get the 5V. It will all be much smaller and more efficient. You can use a cheap MC34063 for the DC-DC converter (you can buy those for cents on for instance).

    • Yeah, I did swap it out after my DC-DC converter chip arrived and the whole thing is much lighter and runs much cooler now :)

        • Hi James,

          I didn’t remove the transformer, I just replaced the linear LM317 with a switching regulator chip (TPS5420). The VFD I used was removed from a piece of junked equipment, it’s FUTABA 13-MT-54NA.

  • Hi, kwong! For one, say “ignorant” in the subject, would there be another way to do all this circuit without using so many pieces?
    I have this display like this and, I would like to make a clock like yours but, I found the circuit very difficult;
    Would you like something easier and also want to use your code – is it possible to use this display?
    If you want to reply in my email, it’s this:
    Thank you very much

Leave a Reply

Your email address will not be published.