This Handy Handheld Unit Converter Doubles as a Fidget Toy

Chad Kapper wanted a fidget toy that could also serve a useful purpose, so he built this handy handheld digital unit converter.

Cameron Coward
2 months ago3D Printing / Productivity

Remember fidget spinners? Before they became a massive hit as a fad toy, they served a purpose that was right there in the name: fidgeting. Many people — especially neurodivergent people — find that fidgeting with small, tactile widgets can help to relieve certain symptoms, like anxiety. Fidget toys fill that market niche and fidget spinners were just one example that happened to gain popularity in the mainstream. But Chad Kapper at Hack Make Mod wanted a fidget toy that could also serve a useful purpose, so he built this handy handheld digital unit converter.

Unit conversion is something we know well in the United States. Almost the entirety of the world uses the sensible metric system, while we insist on hanging onto the quirky imperial system. Anyone who performs any kind of construction or engineering work will likely need to convert measurements between the two — or simply from one metric unit to another. Kapper’s DIY Unit Converter is a dedicated device that makes that process easy, while also doubling as a fidget toy.

The operation is incredibly simple. Other than a rocker switch for power, the only control interface is a rotary encoder. When the device turns on, the user can turn the rotary encoder knob to select a category (like length or mass) and click to select it. They can they do the same to select a specific unit pair (like kilometers to meters). Finally, one more turn of the knob lets them select the measurement. The interface and results show up on a no-nonsense 128×64 OLED screen.

The brain of the device is a NodeMCU D1 Mini-style ESP8266 development board. That might be slightly overkill, since this doesn’t require an internet connection or much processing power. But those boards are very affordable. The battery is from a disposable vape, while the rotary encoder and OLED are generic components.

The 3D-printable enclosure is a nice design with plenty of physical details to provide tactile sensations. And we’re sure that the rocker switch and knob are satisfying to fidget with in-between conversions.

Cameron Coward
Writer for Hackster News. Proud husband and dog dad. Maker and serial hobbyist. Check out my YouTube channel: Serial Hobbyism
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