New Product - VFD Moduar Clock IV-4 6-digit


Now available in our store: VFD Modular Clock IV-4 6-digitand matching acrylic enclosure.

This new shield design for the VFD Modular Clock is a variant of the original IV-4 shield, but with 6 digits. IV-4 tubes are Russian 16-segment VFD tubes, and can display numerals and the letters A-Z.

We've also designed a completely new enclosure for the IV-4 6-digit shield. It uses 2mm semi-transparent blue acrylic, and is designed to give a low-profile rounded appearance.

Creating a 6-digit IV-4 shield without redesigning the base board presented a unique challenge: The HV5812 driver used to drive the VFD tubes has 20 channels. IV-4 tubes are 16 segment displays, 20 - 16 = 4, so in other words the HV5812 driver can only support 4 IV-4 tubes.

Fortunately, there are two free GPIO pins that are available for use by shields, so we decided to use those to drive the two extra digits. To drive VFDs, we need a push-pull driver, for example a combination of a NPN and a PNP transistor. We used the approach described for the In-Grid clock, on this page.


  • Directly compatible with base board version 2.0 and above. Firmware version 1.3 or later required (released 2014.04.20) - Clocks in our shop already ship with the correct firmware.
  • Not compatible with base board version 1.0. (It is possible to get it to work, but will require some modifications and hacking both to the base board and the firmware)
  • Compatible with both IV-4 and IV-17 tubes. Currently we are shipping with IV-4 tubes.