You have senses: eyes, ears, skin. You have muscles that move you. A robot has parts for each job too.
Key idea
Sensors are a robot's senses. They measure something: light, distance, touch, sound, tilt. Actuators are a robot's muscles. They make something happen: motors turn wheels, servos move arms, lights glow, speakers beep.
| Sensor (senses) | What it notices |
|---|---|
| Bump switch | Touch: it clicks when pressed |
| Light sensor | How bright it is |
| Ultrasonic sensor | How far away something is, by bouncing sound off it |
| Line sensor | Dark or light floor right under the robot |
| Tilt sensor (accelerometer) | Which way is down |
| Actuator (muscles) | What it does |
|---|---|
| DC motor | Spins around and around, fast; good for wheels |
| Servo | Turns to an exact angle and holds it; good for arms and steering |
| LED | Lights up |
| Buzzer | Makes a beep or a tune |
Why it works
Every robot idea starts with two questions. What does it need to notice? What does it need to do? A robot that waters plants needs to notice dry soil (a soil moisture sensor) and to pour water (a small pump).
Let's think it through
Worked example: Pick the parts
You want a robot that follows a black line on white paper. What sensor and what actuators?
- It needs to notice dark or light floor: a line sensor.
- It needs to move: two motors with wheels.
Answer: A line sensor (or two) and two drive motors.
Worked example: Sensor or actuator?
A servo that opens a robot's gripper. Sensor or actuator?
- Does it measure something, or make something happen?
- It makes the gripper open.
Answer: Actuator.
Common mistake
Calling a motor a sensor because it is part of the robot. Ask: does it notice, or does it do? A motor does.
Try it at home: sensor hunt
Walk through the house with a notebook. Find machines that sense something: a thermostat, an automatic door, a phone screen, a smoke alarm. Write what each one senses and what it does when it notices. You will find a dozen without trying.