SolarRegulatorFun

Simple Solar-Cell 5V Regulator (SolarRegulatorFun)

PS: This README.md content is generated by GitHub-Copilot.

This repository contains a small educational project that demonstrates a photovoltaic (solar panel) to 5 V regulated output using an LTC3119 switching regulator (LTC3119FB device model and library included). The project includes schematic and PCB files (KiCad), LTspice simulation files so you can simulate the regulator behavior, and supporting library PDFs and notes.

This repo is aimed at students and hobbyists who want a compact, practical example of using a switching regulator to make a stable 5 V supply from a solar panel while preserving good efficiency.

What's new / highlights

• Design updated to use the Linear Technology/Analog Devices LTC3119 switching regulator (LTC3119FB). The schematic and LTspice model in this repo use the LTC3119 symbol (U1 in the LTspice schematic).
• An LTspice schematic (SolarRegulatorFun/SolarRegulatorFun.asc) with simulation parameters is included so users can run transient simulations and inspect startup and steady-state behavior before building.
• KiCad project (schematic and PCB) is included (SolarRegulatorFun/SolarRegulatorFun.kicad_sch and SolarRegulatorFun.kicad_pcb).
• Component library PDFs / datasheets used in the project are included in SolarRegulatorFun/CustomKiCadLib/ (for example: 3119fb.pdf).

Repository layout (important files/folders)

• SolarRegulatorFun/
  • SolarRegulatorFun.kicad_sch - KiCad schematic
  • SolarRegulatorFun.kicad_pcb - KiCad PCB layout
  • SolarRegulatorFun.asc - LTspice schematic (simulation)
  • CustomKiCadLib/ - PDFs and library references used by the KiCad project
    • 3119fb.pdf - LTC3119 datasheet / app note used for the design
    • ujc-hp2-3-smt-tr.pdf - footprint/part reference PDFs
• README.md - this file
• LICENSE - project license

Quick start — view and simulate

1. View schematic / PCB

   • Open SolarRegulatorFun/SolarRegulatorFun.kicad_sch and SolarRegulatorFun/SolarRegulatorFun.kicad_pcb with KiCad (recommended KiCad v6 or later). The exact KiCad version used to create the files is indicated in the KiCad file headers; use a recent KiCad release for best compatibility.
   • The CustomKiCadLib folder contains PDFs and footprints used by the project — consult them if KiCad prompts for missing library items.

2. Simulate with LTspice

   • Install LTspice (Analog Devices LTspice XVII or later).
   • Open SolarRegulatorFun/SolarRegulatorFun.asc with LTspice.
   • The included LTspice schematic contains the LTC3119 symbol (U1) and the supporting components. Simulation directives intended for transient behavior are included as comments in the schematic; to run the recommended simulation:
     • Add or enable the following directives in LTspice:
       • .tran 5m startup ; run a 5 millisecond transient simulation to capture startup
       • .softstart .1 ; (optional) cause the model to perform internal soft-start at 10% of nominal time — helps observe startup behavior
     • Note: In the included .asc these directives are shown in the schematic text (you may need to remove a leading "!" if they appear commented-out in the schematic). After enabling the directives, run the simulator (Running -> Simulate).
   • Inspect node voltages, inductor currents, and output ripple. The Rload element in the schematic can be adjusted to test different load conditions (the included config uses Rload=1Ω as a test load). Component values (inductor, capacitors, resistors) are set in the schematic — open the .asc file to see exact values.

Design notes and BOM highlights

• Regulator IC: LTC3119 (LTC3119FB package referenced in CustomKiCadLib/3119fb.pdf)
• Key passive examples from the LTspice schematic (see SolarRegulatorFun.asc for exact values):
  • Inductor L1 ≈ 2.7 µH (value shown in the LTspice schematic)
  • Bulk output cap C3 ≈ 220 µF (electrolytic/low-ESR recommended)
  • Softstart and compensation components are present in the LTspice schematic; follow LTC3119 datasheet recommendations when selecting values for a production design.
• Always cross-check footprints and pad sizes in the KiCad PCB with the manufacturer mechanical drawings in the CustomKiCadLib folder before ordering boards.

Simulate-first workflow (recommended)

1. Open and simulate SolarRegulatorFun.asc in LTspice; adjust the solar panel input (the V1 source) to match the panel expected IV curve or use a PWL source included in the schematic.
2. Validate startup, steady-state output voltage (5 V target), efficiency under expected load, and thermal behavior (where possible) in simulation.
3. Tune component values and compensation networks in the schematic until the regulator is stable with minimal overshoot and acceptable ripple.
4. Update KiCad schematic and PCB, then generate Gerbers for fabrication.

Contributing and notes

• This repo is intended as an educational, refresh project. Contributions, suggestions, or corrections are welcome — open an issue or submit a pull request.
• If you build and test this circuit, please share measured results (efficiency, output ripple, behavior under varying panel illumination) so future readers can benefit.

License See LICENSE in the project root.

Thanks for checking out the project! If anything is unclear or you want the README to include additional sections (assembly guide, test procedures, measured data tables), tell me which sections to add and they will be included.