Arduino-Based Automatic Guitar Tuner

Motorized Tuning Peg Gripper

I controlled the motorized tuning peg gripper using three digital output pins from the Arduino connected to an L293D H-bridge chip. This chip allows us to turn the motor in either direction or stop the motor based on the states of these three pins. One of the pins is called the enable pin, and the motor will only turn when the enable pin is set to high. The other two pins determine the direction of the motor. I connected the circuit as shown below.

Motorized Tuning Peg Gripper

I controlled the motorized tuning peg gripper using three digital output pins from the Arduino connected to an L293D H-bridge chip. This chip allows us to turn the motor in either direction or stop the motor based on the states of these three pins. One of the pins is called the enable pin, and the motor will only turn when the enable pin is set to high. The other two pins determine the direction of the motor. I connected the circuit as shown below.

Digital Input and Output Circuits

The circuit for the push button is a simple switch with a pull-down resistor. The LED display circuit involves 6 LEDs and a current-limiting resistor.

Digital Input and Output Circuits

The circuit for the push button is a simple switch with a pull-down resistor. The LED display circuit involves 6 LEDs and a current-limiting resistor.

Audio Input Circuit

I used the analog input pin ‘A0’ on the Arduino to read the audio signal coming from the guitar. The Arduino Due reads voltages between 0 V and 3.3 V. The signal coming from the guitar, however, is very low in amplitude and oscillates around 0 V, meaning it contains some negative voltages that the Arduino cannot read. To fix this, the input circuit needs to amplify the signal and add a DC offset. The circuit also needs to provide a low pass filter to eliminate high-frequency components from the signal. Any sampled signal should not contain frequencies above half of the sampling rate. Since the tuner samples the audio at a rate of 5 kHz, my circuit eliminates frequencies above 2.5 kHz. I assembled the circuit as shown below.