2 layers

Sih
Faulty404/SLD_Pen-Pad
The circuit uses an LM358 op-amp to amplify signals from a microphone and includes battery charging capabilities using the TP4057 charger IC.
37 parts
Open-source boards designed in KiCad by Faulty404 on GitHub, from 1 repository. A board’s address here is its repository’s there.

Faulty404/SLD_Pen-Pad
The circuit uses an LM358 op-amp to amplify signals from a microphone and includes battery charging capabilities using the TP4057 charger IC.