Low-cost open-source monophasic transcranial magnetic stimulator

This repository contains the design and validation materials for a low-cost monophasic transcranial magnetic stimulation (TMS) stimulator. As of July 2027, the bill of materials (BOM) runs at USD 657.34. The repository includes the electrical design, controller firmware, and terminal control interface, fabrication files, LTspice simulations, raw magnetic-field measurements, and analysis code to characterize the system. CAUTION This system contains a high-energy capacitor bank and generates high voltages and strong, rapidly changing magnetic fields. Contact with the system can cause severe injury or death, and stored energy can remain after charging is halted. Never rely on the computer interface or firmware as the primary safety mechanism. Work must be performed by trained personnel. Do not connect this research prototype to a person or animal. System overview: The design separates the build into three voltage domains: control domain, power domain, and high voltage domain. The domains are isolated from each other. The Arduino lives in the control domain and sends signals to the other two domains to control charging and discharging. See the complete schematics/tms_schematic.pdf for a more detailed understanding of the circuit. Repository contents: 2d_models/ -- FreeCAD, SVG, PDF, and PNG fabrication drawings for the coil windings and busbars 3d_models/ -- FreeCAD sources and printable STL files for the coil winder and pickup coil helpers controller_arduino/ -- Arduino UNO R4 Minima firmware and the Python terminal user interface data_processing/ -- Raw oscilloscope captures, acquisition scripts, data analysis notebooks, SimNIBS helpers, and generated figures figures/ -- Build, software-interface, and validation figures used in this README schematics/ -- KiCad project, hierarchical schematics, and a three-page PDF export simulations/ -- LTspice models for the charger, discharge path, gate driver, and IL300 linear optocoupler Safety_Checklists.pdf -- Project-specific inspection, pre-charge, and de-energization checklists TMS_field_grid.pdf -- Coordinate grids used for magnetic-field measurements requirements.txt -- Pinned Python analysis environment Editable source files are included wherever possible. The PDF, SVG, STL, and PNG files are provided as convenient exports.