How to distribute power from one source to multiple loads?

Question

Arduino

There is an arduino that controls devices that require additional load (relays and others). Some require 9V. Looking for separate power supplies for each new load is not very practical. I would like to get by with one power supply from a laptop of sufficient power and power both the main module and external devices from it so that when the voltage drops on them, this does not affect the power supply of the arduino. What is the best way to do this?

Answer 1

There are two options: either use linear voltage regulators such as 78L09, KR1158EN9, or step-down DC-DC converters, for example, based on LM2596, MC34063.
The first are simple and cheap, but they heat up. Under heavy load, a heatsink is needed.
The latter are more efficient, but more complicated and more expensive.

Answer 2

How many volts in laptop power supply?