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A 3D printed measuring wheel displaying both metric and imperial measurements.

While reading some of the comments on DIY Simple Measuring Wheel with Rotary Encoder by Mirko Pavleski, one in particular stood out. The comment by soorajts suggesting “squeezing it into an attiny and oled display” got me wondering whether I could not only do this but fit all the components inside the hub of the wheel itself.

One idea was to do something like my Twist-to-Set Kitchen Timer. The problem then comes how to connect the handle. Also the gearing would limit how small the hub could be.

The final design that I settled on is still very compact. It eliminates all the exposed wiring and has a easy to read OLED display showing both imperial and metric measurements.

The circuit is designed around a ATtiny1614 microprocessor. It uses very little power when in sleep mode. The rotary encoder contains two sets of contacts which can become quite noisy resulting in incorrect readings. I added a RC network and Schmitt trigger between each contact and microprocessor. This removes any noise generated by the contacts and provides clean switch change signals to the microprocessor. The result is precise and accurate readings. The circuit is powered by a 3.7V 120mA LIPO battery.”

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