🎒 What you need

one cheap hobby servo (SG90 class) and a microcontroller board if you can borrow or share one; otherwise a DC motor salvaged from a broken toy
a battery holder with AA cells, wire, tape and a screwdriver
cardboard or scrap wood for a mount, and an adult present for any cutting or soldering

✋ Do this

SAFETY: low-voltage batteries only — never mains, never a car battery, never a cut charging cable. Do not power a servo directly from a microcontroller's pin if it stalls; give motors their own battery and join the grounds.
Mount the servo firmly to cardboard or wood first. An unmounted servo just shakes itself around and teaches you nothing.
Send it to 0 degrees, then 90, then 180, pausing between. Mark each position in chalk on the board beneath the horn. Those three marks are your proof it obeys.
Now push gently against the horn while it is holding position. Feel it push back. That resistance is a control loop running inside the servo, and it is module 1 in your hand.
Write a function arm_to(angle) that moves it and waits. Then loop through a list of angles. Reuse, do not retype.
Salvage route without a board: run a DC motor from batteries, swap the wires to reverse it, and use your module 3 knowledge to pulse the connection by hand — count your on-time and off-time out loud and watch the speed change.

💡 Why it works

Inside every hobby servo is a tiny closed loop: a potentiometer measures the actual shaft angle, compares it to the commanded angle, and drives the motor until the error is zero. That is why it pushes back when you shove it. You spent five modules learning that loop; now you can feel it resisting your thumb.

🔥 Challenge

Measure the servo's real limits. Find the smallest angle change it reliably makes, and the heaviest load it can hold before it gives up. Write both numbers on the mount.

📖 New words

servoa motor that moves to and holds a commanded angle

actuatorany component that turns a signal into physical movement

groundthe shared reference wire that all parts of a circuit must connect to

🦾

Servo Driver

Tap when you have finished this module.