Shift4Me is an automatic bicycle shifter
These days many of us are turning to bicycling for fun and exercise. While some may enjoy being able to change up the resistance and pedal speed by shifting, if you would instead prefer to be in the ideal gear automatically, then Jan Oelbrandt’s Shift4Me could be just the thing you need.
The add-on device works by determining the rider’s cadence via a magnetic sensor attached next to one of the pedals. If it’s significantly slower than a set range — 60 RPM in the video below — it shifts down to decrease resistance. If higher, it upshifts.
An Arduino Nano is used for control, with a high torque servo to pull and release the cable. More specific information is available by registering on Shift4Me’s forum, and a quick demo is shown here: