Map a physical system

Understand the idea

A physical project is a chain of energy and information. A sensor turns a condition in the world into a signal; a microcontroller interprets that signal; a driver switches energy from a supply into an actuator; the mechanism changes the world.

Draw the boundary around the thing you are studying. Label power separately from signals. A motor can need more current than a microcontroller pin can safely supply, so the controller normally sends a small command to a motor driver instead of powering the motor itself.

Feedback closes the loop: measure what actually happened, compare it with the target, and adjust the next command. Without feedback, the controller can only guess how the physical system responded.

Worked example

For a desk fan speed controller: knob → analog input → controller → motor driver → fan speed → speed sensor → controller. The battery or adapter is the energy source; the knob and sensor are information sources.

Try it at the bench

1. Choose a project you know and draw its signal path with arrows.
2. Use a different color for the power path. Mark every point where power and signal meet.
3. Predict one failure at each boundary: unplugged sensor, reset controller, overheated driver, or jammed mechanism.

Check your understanding

Why put a motor driver between a microcontroller and a motor?