Hi Trish, well there are many. From ancient ASCII schematics to a full-fledged EDA suite like KiCAD (warning, big learning curve.) But for a quick question, many just use a piece of paper and a pencil, or their favorite paint program.
i have a lidar that seems very sensitive to the power source. When powered via the PC's usb it works great. It also works when powered via LM2596, but it doesn't seem to work with a "high-end" step-down regulator like the D36V50F5. pololu.com/product/4091