Regulating Voltage with a DC-DC Buck Converter (LM2596) on a Raspberry Pi 4B

Step by step

1. Drag Raspberry Pi 4B, DC Power Supply, DC-DC Buck Converter (LM2596), a Resistor, and an LED onto the Canvas.
2. Hover over the buck converter's 4 pins to confirm the labels: IN+, IN−, OUT+, OUT−.
3. Wire the input side: DC Power Supply's + → the converter's IN+. DC Power Supply's − → the converter's IN−.
4. Wire the output side into a simple load, the same way you'd wire any regulated power source: converter's OUT+ → a Resistor → the LED's anode. LED's cathode → the converter's OUT−. Wire the converter's OUT− → a Pi GND pin too, so the whole circuit shares one common ground.
5. Click the DC Power Supply to select it and set its output — try 12V, a realistic real-world input for this kind of module.
6. Click the buck converter to select it, open its settings panel, and try the first preset: 5V / 5A. This is what a real LM2596 module set for a standard 5V rail looks like.
7. Click Start — no Python code is needed for this circuit, since the LED is lit entirely by real wiring, the same zero-code behavior a Pi power pin already has.

The LED lights at full brightness. The converter's own on-canvas readout shows the real regulated output — 5.00V, unaffected by the 12V input, because a buck converter always steps voltage DOWN toward its own set point, never up and never past its input.

8. Click Stop, reselect the converter, and switch its setting to the second preset: 4V / 5A. Click Start again — the LED is dimmer now (still lit, just less brightly, following the same resistor-aware brightness this simulator already applies to every LED), and the readout shows 4.00V.
9. Click Stop, switch to the third preset: 5V / 2A, and set the DC Power Supply down to 3V (lower than the converter's own 5V set point). Click Start again.

Check the Console — you should see a warning that the output has been clamped to the input voltage. This is a real, physical fact about a buck converter: it can only step voltage DOWN, never up. With only 3V coming in, it cannot produce 5V no matter how it's set — the readout shows 3.00V, not 5.00V, and the warning explains why.

10. Click Stop, set the DC Power Supply back to 12V, and click Start one more time to confirm the readout returns to a clean 5.00V with no warning.

What “working correctly” looks like

• Output voltage always matches the settings-panel value, UNLESS the input voltage is lower — in that case the output is clamped to whatever the input actually is, and the Console logs a warning explaining the clamp.
• Changing the DC Power Supply's own voltage never raises the buck converter's output past its own set point — only ever down toward it, or exactly at it once the input is high enough.
• A wired load that would draw more current than the Rated Current setting causes the output voltage to sag below the set point — a real "constant-current" foldback, not a hard cutoff — and the Console logs a warning naming both the demanded current and the rating.
• With no load wired at all (OUT+ genuinely unconnected to anything with a path back to OUT−), the converter still reports its own regulated voltage — a real buck converter regulates whether or not something is drawing power.
• A dead short (OUT+ wired directly to OUT− or GND with nothing else in between) folds the output all the way to 0V, not a crash or an error.

If something’s wrong

• Output always reads 0V → confirm IN− is genuinely wired back to a real ground (the DC Power Supply's − pin, ultimately reaching a Pi GND pin somewhere in the circuit) — the converter needs a real return path before it will regulate anything, the same as any other powered module in this simulator.
• Output matches the input exactly instead of the settings-panel value → double-check you're reading the converter's OWN readout, not the DC Power Supply's — and confirm Start was clicked again after changing the settings panel, since a change only takes effect on the next run.
• LED never lights even though the readout shows a real voltage → check the LED's anode/cathode orientation, and confirm OUT− is wired back to the same ground the LED's cathode side ultimately reaches — a floating return path on the load side breaks the circuit even if OUT+ itself is correctly wired.
• Expecting the output to rise above the settings-panel value when the input is very high → that's the one thing a buck converter can never do, by design — it only ever steps voltage DOWN. Raising the input above the set point does nothing once it's already above it; the output stays pinned at the set point.