Curve tracer

Automated I–V Curve Tracer Bench — KiCad Schematic & PCB

Location: kicad_project/
KiCad Version: 10.0.6 (Fully compatible with KiCad 8.x / 9.x / 10.x)
Verification Status:

• ERC (Electrical Rules Check): 0 Errors, 0 Warnings (100% PASS)
• DRC (Design Rules Check): 0 Errors, 0 Warnings (100% PASS)
• Unconnected Items: 0 Unconnected Pads (100% ROUTED)

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1. Quick Start: Opening the Project in KiCad

1. Launch KiCad and choose File → Open Project...
2. Navigate to this folder and select:

   curve_tracer.kicad_pro

3. From the KiCad Project Manager:
   • Click Schematic Editor to open curve_tracer.kicad_sch
   • Click PCB Editor to open curve_tracer.kicad_pcb

[!NOTE] All custom breakout board symbols (MCP4725, ADS1115) are self-contained in curve_tracer.kicad_sym and pre-configured in sym-lib-table. Opening the schematic on any system requires no external symbol libraries.

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2. Visual Reference Files (Breadboard Assembly)

If you don't have KiCad open or want printable / high-res visual references while wiring your breadboard, use the pre-rendered files in this folder:

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3. Breadboard Circuit Wiring Guide (Pin-to-Pin Reference)

This table provides the exact wiring map to transfer the KiCad schematic to a solderless breadboard:

A. Arduino Uno R3 Connections

B. DAC Breakouts (MCP4725)

C. Op-Amp Buffer (MCP6002 Dual Rail-to-Rail)

D. ADC Breakout (ADS1115 16-Bit 4-Channel)

E. Range Selection Relay & Transistor Driver

F. Drive Selector Header (J1) & DUT Socket (J2)

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4. Four Critical Breadboard Rules (From Simulation Auditing)

1. Kelvin Ground Return:
   Do NOT daisy-chain the DUT Source (J2 Pin 3) through random breadboard ground rails. Breadboard spring contact resistance of $0.2\text{ to }0.5,\Omega$ creates negative source degeneration, inflating $R_{ds(on)}$ measurements by $>8%$.
   Action: Run a dedicated, short wire directly from the DUT Source terminal to the ADS1115 GND pin.

2. I²C Pull-Up Resistors (SC-1):
   The three breakout modules (MCP4725 $\times 2$, ADS1115) already contain on-board $10\text{ k}\Omega$ pull-up resistors on SDA and SCL, yielding an effective parallel pull-up of $3.33\text{ k}\Omega$ (well within the $3\text{ mA}$ I²C sink limit).
   Action: Do NOT populate discrete resistors R8 and R9 ($4.7\text{ k}\Omega$) on the breadboard (mark them DNP).

3. Decoupling Capacitors (SC-4):
   Breadboard rails have significant inductive reactance.
   Action: Place a $100\text{ nF}$ ceramic capacitor directly across the $V_{CC}$ and $GND$ pins of each breakout board (U2, U3, U4) and the MCP6002 op-amp (U5).

4. Power Supply Headroom (T2 Failure Resolution):
   The unbuffered MCP6002 op-amp output stage drops $\sim 400\text{ mV}$ at $10\text{ mA}$. If powered from standard laptop USB that droops to $4.75\text{ V}$, the maximum reachable $V_A$ is $4.345\text{ V}$ (causing clipping on $4.50\text{ V}$ commands).
   Action: Power the Arduino from an externally powered USB hub or regulated $5.0\text{ V}$ bench supply so that $V_{DD} \ge 4.95\text{ V}$, or limit software test sweeps to $4.30\text{ V}$.

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5. Verification Proofs

The schematic and PCB layout have been formally verified using kicad-cli 10.0.6:

• ERC Verification (erc_report.rpt):

  ***** Sheet /
   ** ERC messages: 0  Errors 0  Warnings 0

• DRC Verification (drc_report.rpt):

  ** Found 0 DRC violations **
  ** Found 0 unconnected pads **
  ** Found 0 Footprint errors **