MEMS SensorsAn introduction to MEMS sensors, current applications, and their future

Presented by Jennifer ChinSeptember 2nd, 2016

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Preface

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MEMS SensorsA system that uses mechanical devices and electrical signals

Micro

Electrical Sensing

Mechanical

Systems

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How they Sense Capacitive Sensing

Measures properties of conductive material

Piezoelectric SensingMeasures properties by converting mechanical force into electrical charge

Piezoresistive SensingMeasures properties by converting mechanical force into electrical resistance 4

Active SensorsActively scans surroundings and compiles data to compare and

measure changes

Relies on transmissions and feedback to detect changes in the area of coverage

Sends out a signal (i.e. microwave pulses, ultrasonic frequencies, or radio waves) that bounces off a target, and gathers data from the sensor upon reflection

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Passive SensorsDetects and responds to inputs from the physical environment without

producing any transmissions

Passive sensors activate after detecting environmental inputs such as vibrations, light, radiation, heat, or other physical signals occurring in the sensor’s environment

Ex. Mechanical Sensors

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Types of MEMS Sensors

1.Inertial

2.Optical

3.Pressure

4.Chemical

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Sensors in Use Today

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iPhone 5s and Up

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Main Sensors

1.Three-Axis Gyroscope

2.Accelerometer

3.Proximity Sensor

4.Ambient Light Sensor

5.Touch ID Fingerprint Sensor

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4

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1

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3-Axis Gyroscope and Accelerometer- Gyroscope: Sensor that assumes

orientation through spinning wheel with free axis rotation

- Uses: Autofocus on camera and landscape viewing of photos and keyboard

- Accelerometer: Sensor that measures acceleration of a moving or vibrating object

- Uses vary from Maps application to pedometers to app store games

Passive/Inertial

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Proximity Sensor

- Shuts off illumination and touch sensitivity when sensor is activated

- How it Works: Emits an electromagnetic beam and looks for changes in the return signal

Active/Optical11

Ambient Light Sensor

- Senses lighting and adjusts screen brightness accordingly

- How it Works: Uses a photodiode that converts light into current and voltage

- Can perceive brightness just as our eyes can

Passive/Optical12

Touch ID Fingerprint Sensor- Scans finger to unlock iPhone

- How it Works: Uses capacitive sensing to scan and read fingerprint

- Capacitive Sensing: When a finger hits the screen, an electrical charge is transferred to the finger. This completes the circuit, creating a voltage drop at a specific point on the screen.

Passive/Capacitive13

iRobot: RoombaUses sensors to navigate itself throughout room and vacuum

Main Sensors:

1.Infrared Transmitter/Receiver

2.Object Sensor

3.Cliff Sensors

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1

3

2

Infrared Transmitter/Receiver

- Roomba uses infrared transmitter and receiver to roughly map out and measure the room

- How it Works: The sensor sends out an infrared signal through the transmitter and analyzes the return time to the receiver

Active/Optical15

Object Sensor

- When Roomba bumps into a wall or an object, it backs up and changes direction

- How it Works: Behind the bumper is the object sensor. When the bumper retracts the object sensor is activated

Passive/Inertial16

Cliff Sensor

- Roomba uses cliff sensors to avoid going down stairs

- How it Works: The cliff sensors send out infrared signals. If they do not return immediately, Roomba changes direction.

Active/Optical17

Collaboration of Sensors

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Apple Watch: Heart Rate SensorMeasures heart rate throughout the day so users can check it at a glance

Main Sensors:

1.Green LEDs

2.Infrared Light Blasters

3.Photodiode Sensors

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Method 1: Green LEDs*1.Green LEDs flash hundreds of times per second

2.Photodiode Sensor measures the absorption of the LEDsa. Red blood absorbs green light and reflects red light

b. When blood is flowing, the absorption is higher than in between heart beats

* High power consumption

Active/Optical 20

Method 2: Infrared Light Blasters*1.Infrared Light

a. Shoots out to measure heart rate about every 10 minutes

2.Photodiode Sensor measures the absorption of infrared lighta. Non-visible light can also be absorbed

b. Same concept as Method 1

* Not as reliable as Green LEDs

Active/Optical21

Sensors in the Future

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SCiO: Molecular Sensor

Reads the chemical make up of materials using Near-Infrared sensors

Main Sensor:

1.Near-Infrared Sensor (NIR)

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Near-Infrared (NIR) SensorSCiO uses the NIR optical sensor to read and analyze the chemical make up of organic materials

How it Works: The NIR sensor emits a near-infrared light that is then reflected back from the object. The NIR light is broken down into a spectrum and read by the transmitter

Optical/Active24

Structure Sensor (3D Scanner)

Portable device that takes a rapid 3D scan of objects and people

Main Sensor:

1.Infrared Sensor

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Infrared (IR) SensorStructure Sensor uses two infrared sensors to measure the depth and distance of objects in order to create a 3D scan.

How it Works: The IR sensor uses a specific receiver selected to read the IR signal. The receiver measures the intensity of the return signal and determines the distance of the object

Active/Optical26

謝謝你的照顧和教導

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