A DIY vacuum fluorescent display driver

vfd_driver1

Kerry Wong posted an update on his vacuum fluorescent display driver we covered earlier:

As I mentioned before, there are many driver chips (e.g. MAX6921, MAX6931) readily available for interfacing with VFDs. The driver circuit I am showing here is a bit more complex as it uses only the generic 74HC’s and discrete transistors.

The basic technique for driving a multiplexed VFD is very similar to that for driving a 7-segment LED display. The major difference is the voltage requirement for the control gates and segment. For a VFD, the driving voltage is typically between 20V and 30V instead of the TTL or CMOS logic level used for driving 7-segment LED displays. Thus we must employee some kind of voltage shifting circuitry to translate the logic level signal into the voltage required by the VFD.

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