Pitcher : An automatic guitar tuner

Abstract: Pitcher is a prototype which makes it easier for inexperienced guitar players to tune their guitars without any prior knowledge required. This thesis will explore how the construction varies between the usage of DC and a stepper motor, how reliable the tuner is and how long it takes to tune the guitar. The tuner will capture sound with a microphone and calculate the current frequency of the string with YIN autocorrelation. Based on the frequency a control system regulator is used to determine the speed and direction of a motor which turns the tuning peg, this is repeated until the string is in tune. 30 tests were conducted from different starting frequencies, and the time it took for the tuner to find the right pitch and the string’s corresponding frequency was measured. Some of the measurements were a couple of Hz off pitch, and only about half of the frequencies measured belonged to the interval where there is no noticeable dierence of the pitch, therefore the tuner could not be considered reliable. The time it takes to tune the guitar is dependent on how far off pitch the string is andthe dierence in time does not depend linearly with the starting frequency, it increases faster the further off pitch the string is.The tuner is portable and to apply the tuner to the guitar it is held and placed on the tuning peg with one hand as the other hand is plucking the string.