Share a mini piano circuit

A Minano or mini-piano actually produces organ-like notes, rich in harmonics, and is very pleasant to the ear. This instrument can be a lot of fun.

It may create only one tone in a period, thus simplifying the performance as there are no chords involved or the need to strike multiple tunes simultaneously.

Feedback through capacitor C1 across the collector of the 2N2222 and the base of the BC547 is responsible for generating the oscillation.

The value of the capacitor determines the frequency of the circuit and can be changed as required. The R1 value cannot be changed as it should be fixed with the minimum required value to ensure the highest frequency note.

To get the lower frequencies or tunes, some adjustments in the form of A, B, C, D presets were added to the design.

As the resistance adjustment on the preset increases, the frequency will decrease.

A calibration of about 2 octaves based on middle C will be fairly fine and will cover 128 to 512

You'll actually find a variety of frequency ranges that apply, popular ones are probably standard and concert pitch.

For these ranges, the 100K resistor value on the preset is usually sufficient.

keyboard

The picture above depicts the keyboard of a mini-piano, which has a little over one octave.

For the actual implementation of the keyboard, make sure that the keys are at least 25 mm apart and have no sharp edges.