In Japan’s vast and highly specialized electrical equipment industry, safety is paramount. Every day, thousands of installations are performed to ensure the stable delivery of power—from transformers to relay coils, across factories, buildings, and infrastructure. Yet, one of the most basic but critical tasks during these installations is often overlooked: correct wiring polarity.
For decades, a unique analog buzzer device originally produced by Panasonic (formerly National) had quietly become a staple in Japan’s electrical field. Though not intended for miswiring detection, its 3V open-circuit voltage and 20mA short-circuit current, combined with an analog oscillator circuit, allowed it to detect impedance differences in transformers and relay coils. It became indispensable for engineers and electricians nationwide—simple, battery-powered, and safe for sensitive equipment.
However, in the 2010s, Panasonic discontinued the device, and the market was left without a suitable replacement. New digital testers lacked the core detection ability. While they could measure resistance thresholds, they couldn’t detect inductive miswiring in complex electrical components.
It was clear: this legacy device needed to be reborn—with improvements fit for the 21st century.
🚀A Hybrid Redesign from Scratch, Powered by Expertise
To fill that gap, a team of Japanese engineers collaborated with veteran circuit designer Mr. Shimotsuma (下間憲行known as “居酒屋 Garage”), is a well-known circuit design and programming specialist in Japan who has contributed technical articles to Transistor Technology magazine(https://toragi.cqpub.co.jp/) for decades, widely read by Japanese engineers. Starting from a modern microcontroller-based continuity tester, they worked together to reintroduce the lost AC-based detection principle. By integrating an oscillation circuit and testing various frequencies, the redesigned device could now detect even low-inductance components like modern analog meters and small relay coils.
The result: a compact, battery-powered, AC/DC hybrid tester that wakes automatically when terminals are shorted—safe for field use and highly efficient for daily inspections.
Realizing that the original buzzer’s unique ability lay in impedance-based detection via AC oscillation, the team asked Mr. Shimotsuma to develop a hybrid device that included both AC and DC modes. Over a series of rapid design iterations, he added oscillation circuits and adjusted frequencies from 1kHz to 5kHz—gradually enabling detection of components that had previously gone unnoticed.
The device retained a cleverly efficient sleep-mode design 💤, waking automatically when the test terminals were shorted ⚡ and featuring a 180-second timer ⏱️ to return to sleep—eliminating the need for a power switch 🔌—and, with a sleep current under 1 μA powered by two AA batteries , could last for weeks even if forgotten, ensuring the new buzzer preserved the beloved field usability of its predecessor.
🔄From Prototype to Production — With Seeed Fusion PCBA
With the electronics design complete, the next hurdle was manufacturing.
💡 Traditional PCB production in Japan would have been prohibitively expensive for low-volume runs.
🚀 Instead, the team turned to Seeed Studio Fusion PCBA, which allowed them to:
✅ Rapidly prototype with minimal upfront cost
✅ Complete 95% of assembly via automation
✅ Receive production-ready boards in just 25 days
✅ ⏱ Or as fast as 16 working days with expedited service
✅ 📎 Share your PCB/PCBA projects with just one click – perfect for collaboration!
Seeed’s integrated services helped the team turn their concept into reality faster, easier, and more affordably than ever before. 🌱
“Seeed Fusion PCBA made it possible for us to turn a legacy idea into a modern product—affordably, and without compromise. It’s an empowering service for small-scale innovation.”