IV-1

The IV-1 (ИВ-1 rus.)  is a Soviet vacuum fluorescent display (VFD) tube designed for the formation of signs (point and dash) in electronic devices . It is commonly used as a separator tube in multi-digit VFD clock projects, typically for displaying the alarm on/off indicator or as a colon separator between digits .

The tube has a distinctive green glow and features flexible wire leads rather than a plug-in socket .

Thanks to its characteristic green glow, which matches that of other Soviet vacuum fluorescent displays, the IV-1 tube is typically used alongside IV-11, IV-12, or IV-22 tubes.

Technical specifications:

• Glow intensity: not less than 500 cd/m²
• Number of segments: 2
• Viewing angle: more than 60°
• Anode-segment current in static mode: no less than 0.25mA
• Anode current total: no less than 0.6mA
• Heating voltage: 0.85 ± 0.15 V
• Anode and grid voltage in static mode: 20 – 25V
• Anode and grid voltage in pulse mode: 50 – 70V
• Ready time: no more than 1 sec.

Minimum operating time: 3000 h.

ATTENTION: The IV-1 tube filament requires a voltage of only 0.7–1.0V; applying 5V directly will burn out the filament. Always use a current-limiting resistor or a dedicated low-voltage power supply. The operating filament voltage for the IV-1 tube is 0.85 ± 0.15V, which is significantly lower than that of the IV-11 (1.2–1.65V) and IV-22 (1.2V) tubes.

Recommended driver ICs:
MAX6921 / MAX6921AWI: A multi-channel VFD driver; frequently used in IV-11 and IV-22 tube clocks and suitable for driving two segments of an IV-1 tube.
74HC595 + high-voltage transistors: An alternative solution using discrete components.
UDN2981A: A high-voltage high-side (source) driver; used in some IV-11 tube clock designs.