XIAC Museum — 2012 — Kopriso “Cold War” Nixie Tube Wristwatch (AU-2012)

The story

When finances were tight, I applied the same engineering discipline used in industrial retrofits to a much smaller problem: building a wearable instrument that was mechanically robust, electrically efficient, and repeatable to assemble.

The Cold War watch uses two nixie tubes and shows the time in a scrolling sequence. Operation is via high-impedance contact buttons and an IR reflective motion sensor for motion-activated reads.

Model: AU-2012  •  Year: 2012  •  Brand: Kopriso

Documentation:

Original user documentation exists and is supplied with the watch. It is intentionally not published online, as the Cold War watch has become a collector’s item.

Design highlights

• Two-digit display with scroll sequence for easy reading.
• High-impedance touch operation (contact buttons) — simple, sealed, and reliable.
• Motion activation via IR reflective sensor (configurable sensitivity).
• Ambient light sensing to adjust brightness smoothly (512 steps) and avoid wasted power.
• Efficiency-focused HV drive: designed so battery energy goes into display power, not heat.

From the original manual: a 750mAh cell is documented as capable of roughly 20,000 time readings at typical indoor brightness.

Hero image

Cold War (AU-2012). Dual-tube display with integrated “CW” logo derived from Cold War iconography.

Provenance & backplate

Front & back. The hand-engraved case back is part of the artefact — keep it authentic.

Symbol & identity

The “Cold War” theme wasn’t added as decoration — it was integrated into the object’s identity. The hammer-and-sickle motif was reworked to form the letters C and W as a compact visual shorthand.

Museum note: the aim is historical reference, not commentary — the object is preserved as it existed at the time.

Origins — Kopriso (1982)

Kopriso shop sign. Sassenheim, The Netherlands — February 1982.

Kopriso has been a personal trading name since 1982, originally used for small electronics, clocks, and repair work. The Cold War watch continues that same lineage — preserved here as part of the Museum record.

Manufacturing notes

• Case: Olive Drab spray painted or black powder-coated aluminium with stainless steel base plate.
• Controls: contact buttons + motion trigger (no fragile protruding switches).
• Service approach: designed to be opened, serviced, and reassembled without drama.

This same “serviceability first” mindset shows up later in industrial retrofit work — just scaled up.

Related

The Cold War watch is best viewed alongside the later Mi Esposita solar-powered beauty: same designer, different constraints, different answers.

Community & archive:

Independent collector and enthusiast community:

Display brightness and drive capability

The Kopriso Cold War Nixie watch was engineered to deliver an unusually high display brightness for a wearable device. At full output, the tubes were driven beyond 2 mA anode current each at approximately 180 V, placing it at the upper practical limit for Nixie tubes in a wristwatch form factor. Drawn battery current during operation is between 6.5mA and 200mA dependent on ambient light brightness and available battery power. Very easy on the eyes at night, while remaining clearly readable in daylight.

This same energy-aware drive strategy also enabled operation from a CR1216 button cell, dynamically adapting display current to the limited instantaneous energy available rather than relying on fixed drive levels.

Achieving this required a high-power, high efficiency, tightly controlled boost converter, careful thermal consideration, and strict duty-cycle management to ensure the display operated only in short, intentional bursts.

To date, this remains the brightest documented dual tube Nixie wristwatch display. A real-world brightness demonstration is available here: brightness test video .

Why the Kopriso Nixie watch was discontinued

Although the Kopriso Nixie watch proved that ultra-low-power electronics, solar charging, and high-voltage display technology could be successfully combined in a wearable form, real-world use highlighted a fundamental limitation: Nixie tubes were never designed for mobile equipment.

In practice, accidental drops occurred far more often than environmental issues such as moisture ingress. Even when the glass envelope survived an impact, internal metal structures could shift or shed microscopic particles, occasionally leading to cathode shorts or intermittent faults that were impossible to predict or economically repair.

The Kopriso Nixie watches remain the only documented nixie wristwatches capable of operating from a small CR1216 button cell — a result of extreme efficiency-focused design. Video proof of operation .
Despite this, rather than continue producing a device where normal everyday handling could result in costly repairs, the design was deliberately concluded as an exploration of the limits of wearable electronics rather than a compromise in robustness.

Operating instructions

Original operating instructions for the Kopriso Nixie watches have been preserved and are provided here for reference. These documents describe the intended operation, configuration parameters, power-saving behaviour, and calibration features as shipped.

• Mi Esposita — Operating Instructions (PDF)
• Cold War — Operating Instructions (PDF)

Note: Depending on the software release installed at the time of manufacture, some features described in these manuals may or may not be available.

These manuals are published for archival and support purposes and reflect the original design intent at the time of manufacture.