Self-powered wireless digital tachometer scheme without sensors for measuring spin of Yo-yo

A wireless yo-yo system with a digital tachometer function has been developed. The system consists of a self-powered wireless yo-yo and a receiver. The yo-yo contains a micropower generator and a wireless transmitter. Ultralow-power wireless on-off-keying modulation synchronized to the AC output of the generator makes it possible to determine the maximum rotational frequency of the yo-yo from the minimum period of the pulses detected by a receiver without sensors. Another advantage of the antenna of the transmitter of the yo-yo is that the receiver can detect transmitted pulses at any location around the yo-yo, even though the antenna is directional. The antenna acts as a rotational polarization antenna as it rotates along with the yo-yo. This type of antenna makes it possible for the receiver to detect transmitted pulses once every rotation of the antenna. To verify the effectiveness of our self-powered wireless yo-yo with digital tachometer scheme, we made a wireless yo-yo system consisting of a wireless yo-yo with a micropower generator and a receiver with a PC. When the yo-yo is thrown, the PC calculates the maximum rotational frequency and displays the result on the screen at a distance of up to 3 meters.