Stage 00 · Robotics Orientation · Lesson 4 · 40–55 min
Actuators
Actuators are the robot’s muscles. Pick one that is too weak and your arm sags or stalls with a buzzing sound. Pick one that is too greedy for current and your Arduino keeps resetting. Most “my robot doesn’t work” stories in Stage 6 trace back to actuator or power choices.
Torque is force × distance from the pivot. That’s exactly why the long spanner helps. Hobby servo shops usually quote torque in kg·cm: a 2 kg·cm servo can just hold 2 kg at 1 cm from its shaft, or 200 g at 10 cm. Engineers use newton-metres (N·m): 1 kg·cm ≈ 0.098 N·m.