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Your First Simulation

This tutorial walks you through opening, running, and analyzing a circuit simulation in GeckoCIRCUITS.

Duration: 15 minutes

Prerequisites: Installation complete

Step 1: Launch GeckoCIRCUITS

Start the application using your platform's launcher:

./scripts/run-gecko-linux.sh    # Linux/WSL
./scripts/run-gecko-macos.sh    # macOS
scripts\run-gecko.bat           # Windows

The main window opens with an empty schematic editor.

Step 2: Open the Example Circuit

Go to File > Open and navigate to:

resources/tutorials/1xx_getting_started/101_first_simulation/ex_1.ipes

This loads a basic power converter circuit. You should see:

  • Power components (top) - Switches, diodes, passive components
  • Control blocks (bottom) - PWM generators, signal sources
  • SCOPE blocks - Oscilloscope measurement points

Step 3: Understand the Circuit

Before running, take a moment to understand the schematic:

Components You'll See

Component Symbol Role
DC voltage source Circle with ± Provides input power
MOSFET switch Triangle with gate Controlled switching element
Diode Triangle with bar Freewheeling current path
Inductor (L) Coil symbol Stores energy, smooths current
Capacitor (C) Parallel plates Filters output voltage
Resistor (R) Zigzag Load
Ground Three lines Reference node
SCOPE Rectangle Measurement display

Viewing Component Parameters

Click on any component to see its dialog with parameters like:

  • Resistance, inductance, capacitance values
  • Voltage/current source settings
  • Switch timing and control signals

Step 4: Configure Simulation

Open the simulation settings via Simulation > Settings or click the settings icon.

Key parameters:

Parameter Meaning Typical Value
Total time (T) How long to simulate 10 ms
Time step (dt) Computation interval 1 us
Solver Numerical method Backward Euler

Time Step Rule

The time step should be 100x smaller than the switching period. For 100 kHz switching: dt < 0.1 us

Step 5: Run the Simulation

Click Run (play button) or press F5.

Watch the progress bar - the simulation computes all circuit variables at each time step.

Typical simulation time: 1-5 seconds for simple circuits.

Step 6: View Results

Double-click any SCOPE block to open the oscilloscope window.

Reading the Oscilloscope

The scope displays voltage and current waveforms over time:

  • X-axis - Time (seconds)
  • Y-axis - Voltage (V) or Current (A)
  • Multiple channels - Different colors for different signals

Scope Navigation

Action Control
Zoom in Scroll wheel up
Zoom out Scroll wheel down
Pan Click + drag
Auto-scale all axes Right-click > Auto Scale
Add cursor Right-click > Cursor

Step 7: Analyze the Results

For a buck converter, you should observe:

  1. Output voltage - Settles to V_out = D x V_in
  2. Inductor current - Triangular ripple waveform
  3. Switch voltage - Rectangular pulses between V_in and 0

What to Check

  • Does the output reach steady state?
  • Is the ripple within acceptable limits?
  • Are there any unexpected spikes or oscillations?

Step 8: Experiment

Try modifying the circuit:

  1. Change duty cycle - Click the PWM block, adjust D
  2. Change load - Click the resistor, change R
  3. Change inductance - Click the inductor, change L
  4. Re-run and compare results

Undo

Use Edit > Undo (Ctrl+Z) to revert changes.

What You've Learned

  • How to open and navigate circuit files
  • How to configure and run simulations
  • How to view and interpret waveforms
  • How to modify circuit parameters

Common Issues

Problem Solution
Simulation doesn't start Check all nodes are connected, ground exists
Output is zero Check switch control signal, duty cycle > 0
Waveform oscillates wildly Reduce time step, check component values
Scope shows nothing Double-click scope to open, check channel assignments

Next Steps