| Need |
Good first choice |
Notes |
| Drop 12V to 5V for logic |
DC-DC buck converter (e.g. LM2596) |
More efficient and cooler than linear 7805 regulators, especially with higher currents. |
| Boost a single 18650 to 5V |
Boost converter or USB step-up module |
Great for power banks, portable WiFi/LoRa nodes, and small LED projects. |
| Input varies above & below target |
Buck-boost (step-up/step-down) converter |
Keeps output steady even when the battery crosses above/below the desired voltage. |
| Powering Raspberry Pi |
5V buck converter rated 3A or higher |
Use thick wires and keep cable short to avoid undervoltage warnings on Pi. |
| Motors, pumps, and servos |
Higher-current buck/boost with heatsink |
Check stall current of motors and leave headroom (30–50%) on converter rating. |
| Bench supply / test rig |
Adjustable buck or buck-boost with display |
Lets you dial in different voltages for quick prototyping on the bench. |
| From car or solar sources |
Wide-input buck or buck-boost |
Look for modules with automotive/solar-friendly input range (e.g. up to 30–40V). |
Values and picks are common starting points; check each product page for exact voltage/current ratings and safe wiring.
