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Making a clock using VFD display tube IV-6 and MM5316N

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I'm going to make a watch out of an IV-6 that I bartered with a retro display tube enthusiast in Ukraine.

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Putting the VFD on the board

The IV-6s I bartered are used, so I cleaned up the leads so that I could insert them into the board.

I lined up four of them and was able to stand them on the board. I attached a pin header to the back so I could stick it into the breadboard. This alone is pretty cool.



The MM5216N is a clock IC for VFDs.


You can connect a VFD directly to the IC and make a clock just by connecting a power supply, a clock, and a switch.

The most important thing to note about this IC is the power supply pins. The power supply pins, VSS and VDD, are different from what we are used to.

  • VSS: + pole 25V applied
  • VDD: Connect to GND

Nowadays, you would expect VDD to be the + pole and VSS to be GND, but they are opposite. I made a mistake once and connected them in opposite directions?

The circuit


For now, let's make a circuit where the IC is only connected to the power supply and VFD, and the numbers are displayed.

I wired up the IC and DCDC converter on a breadboard.

Plug in the VFD board that we made earlier.

It glows!

I didn't connect the clock, so it doesn't advance the time, but it did display the numbers!

Also, the heater of the VFD is not driven by AC, so the right digit is brighter and the left digit is dimmer.

In the next article, I'll try to create a clock source and add the ability to drive the VFD AC.

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