Mechatronics Hardware Overview
Movement
Continuous rotation
DC motors: When paired with a gearbox, DC motors are a great way to get a set of wheels moving
Pros – relatively easy to use, wide variety of sizes and powers
Cons – require a separate driver circuit, can draw excessive amounts of current if stalled
Continuous servo: Basically a DC motor with a gearbox and a built-in motor driver in one package
Pros – easy to get started, inexpensive
Cons – slow, hard to control accurately
Limited rotation with position control
Hobby servo: Easily set the position of a shaft with typically a 90 or 180 degree range of motion
Pros – inexpensive, wide variety of sizes, easy to use
Cons – durability (some models), chatter, limited turning range
Continuous rotation with position control
Stepper motor: Rotates a shaft one increment at a time to provide position control
DC motor with encoder: Uses an encoder to measure the output position of a DC motor (typically with a
gearbox) and a closed-loop control system to control the output position
Linear Motion
Solenoid: Great for linear motion when only one out of two positions in needed at a time
Linear actuator: Provides better positioning accuracy (for models with position feedback) than a
solenoid, and can hold a position without drawing current
Sensing
Displacement/ Distance
Potentiometer: Measure rotational or linear position
Encoder: Measure continuous rotational (typically) position
IR sensor: Measure distance to an object without contact
Pros – inexpensive, easy to use, contact not needed
Cons – short lifespan, electrical noise, doesn’t detect some surfaces (especially reflective surfaces)
Ultrasonic sensor: Measure distance to an object without contact
Temperature
Analog temperature sensor: Easy-to-use temperature sensor
Pros: Easy to interface, typically factory calibrated
Cons: Limited temperature range
Thermistor: Resistor that changes resistance with temperature
Pros: Very inexpensive, fairly easy to use
Cons: Non-linear
Thermocouple: Rugged temperature sensor
Pros: Very durable
Cons: Difficult to interface (requires separate amplifier), electrical noise
Force
Strain gauge/ load cell: Can provide very accurate force measurements
Pros: Can be very accurate, strain gauges are fairly inexpensive
Cons: Difficult to interface (requires separate amplifier)
Force sensitive resistor: Resistor that changes resistance with different levels of force
Pros: Easy to use, inexpensive
Cons: Poor accuracy
Piezo element: Useful for measuring vibrations and makes a good knock/ impact sensor
Pros: Inexpensive, easy to use
Cons: Cannot measure static loads
User inputs and outputs
Inputs
Momentary switch: Used to create buttons that (typically) make a connection when pressed by a user
and break the connection when released
Pros – Easy to use, inexpensive
Cons – Switches can make and break contact more than once each time the user presses the switch (also
known as switch bounce)
Potentiometer: Useful for creating knobs for users to set parameters
Pros – easy to use, inexpensive
Cons – limited rotation (most models)
Outputs
LCD display: Display a small amount of text
Pros – Easy to use
Cons – Somewhat delicate, some models with a parallel interface take up many microcontroller pins,
only small amount of text can be displayed
LED: Create light
Pros – inexpensive, wide variety of sizes and colors, efficient
Cons – limited viewing angle
Buzzer: Create sound
Pros – easy to use
Cons – poor sound quality