Electronics Lecture Sensors

Welcome

L/O/G/O

Sensing the world

Product Dynamics, L-E-2, Sensors

IO2022

Prof. Dr. Ir. J.M.P Geraedts

Dr. Y. Song, Martin Verwaal, Adrie Kooijman, Ir. Sander Minnoye

Faculty of Industrial Design Engineering

Delft University of Technology

Table of Contents

What is a sensor?

Case study

Workshop

Summary

01

02

03

04

What is a sensor

01

Transducers

A device that converts a

primary form of energy into a

corresponding signal with a

different energy form

It includes:

Sensor and Actuator

Transducers

Sensor

Actuator

Controller

Electronics sensors

Convert desired

parameter into

electrically

measurable signal

Electronics Sensors

The scopeA

rch

ite

ctu

re o

f th

e p

roto

tpye

Sensor Controller Actuator

Physics

Modality

Specificat ions

Costs

Behaviour Transform?Acquire

information

Process

information

Make

decision

LDR LEDArduino

Prototyped by

ActuateTransform?

Sensors

How can we select the right one?

How can we use it?

Case study

02

Parrot AR Drone

Case study

In the next generation

of AR.Drone, Parrot

want to detect

accurate rotor speed.

You are asked to

design a system to

find the rotor speed.

Case brief:

System

RPM

The rotor

We need a sensor

Sensor

Sensor Controller

Mechanical quantities: displacement, Strain, rotation velocity, acceleration, pressure, force/torque, twisting, weight, flow

Thermal quantities: temperature, heat.

Electromagnetic/optical quantities: voltage, current, frequency phase; visual/images, light; magnetism.

Chemical quantities: moisture, pH value

Attributes of Sensors

Embedded technologies that make sensors

function, such as electro-optics, electromagnetic,

piezoelectricity, active and passive ultraviolet.

Operating Principle

Example:

pulse oximetry

Operation principle may differ regarding one

type of measure

Measurements of size, shape, and position

Displacement sensor


The number of dimensions of physical variables.

The physical volume of sensors.

The measuring feature of data in time;

continuous or discrete/analog or digital.

Dimension of Variables

Size

Data Format


Capabilities of on-board data processing and

decision-making.

Intelligence


Capability of generating vs. just receiving signals.Active versus Passive Sensors


The way sensors observe the disturbance in

environment.

Physical Contact

Measure Displacement

Contact

Non-contact


Will the sensor robust enough for its operation

conditions

Environmental durability

Specifications of Sensor

Accuracy

Text

Precision

Resolution

Sensitivity

Resolution

The smallest increment of measure that a device can make

Resolution

Accuracy

Error between the result of a measurement and the true value being measured.

Accuracy

Sensitivity

The ratio between the change in the output signal to a small change in input physical signal.

Sensitivity

Repeatability/Precision:

The ability of the sensor to output the same value for the same input over a number of trials

Precision

Accuracy vs. Resolution

True value

measurement

Accuracy vs. Resolution

Accuracy vs. Precision

Other Specifications

Dynamic Range

•The ratio of maximum recordable input amplitude to minimum input amplitude, i.e. D.R. = 20 log (Max. Input Ampl./Min. Input Ampl.)

Linearity

• the deviation of the output from a best-fit straight line for a given range of the sensor

Transfer Function (Frequency Response):

•The relationship between physical input signal and electrical output signal, which may constitute a complete description of the sensor characteristics

Bandwidth

•The frequency range between the lower and upper cutoff frequencies, within which the sensor transfer function is constant gain or linear

Noise

•Random fluctuation in the value of input that causes random fluctuation in the output value

Response time

The time taken by a sensor to approach its true output when subjected to a step input is sometimes referred to as its response time

Response time

Same as:

Mass-Spring-Damper system

Sett

ling

tim

e b

and

tp

Mp

Xss

0.9Xs

s

0.5Xs

s

td

0.1Xs

s

10-90% rise time

Xmax

Ste

ad

y-s

tate

err

or

Desired steady

state response

Xds

t ts00

System2

2

0 0

( ) ( )2 ( ) step

d x t dx tx t f

dt dt

Actual steady

stateMaximum overshoot ratio

Suppose we got such a response regarding a step function

Ref. William Palm III, System Dynamics, McGraw-Hill Science/Engineering/Math; 2 edition, January 26, 2009

max

ss

ss

xA

x x

Damping ratio

22

ln

ln

A

A

Natural frequency

21n

pt

Response time

Common sensors

Strain Gage

A strain gauge is a

device used to

measure strain on an

object.

Strain gauge

Common sensors

Temperature Sensors

Temperature

Sensor

IC

RTDsResistance Temperature Detectors

Thermocouples

Thermistors

Common sensors

Temperature Sensors

Comparison

Thermocouple vs thermistor

Thermocouple

Wide variety of measuring ranges, including very high limits;

Many physical sizes and configurations;

Fast response times;

Tiny measuring point;

Moderate price; and

Very simple configuration.

Thermistor

Narrowest measuring range, by far;

Lowest stability and linearity;

Accuracy and response time comparable to thermocouples;

Highest sensitivity;

Least expensive; and

Robust signal.

Pressure sensor

Comparison: Resistive vs capacitive screen

From RPM to response time

RPM

Stimulus / sensory Modality

It is one aspect of a

stimulus or what we

perceive after a

stimulus. Some

sensory modalities

include: light, sound,

temperature, taste,

pressure, smell.

Sensory modalityOptic

Magnetic

Within the same modality

How can you

configure of your

sensors?

Setup

Direct

Reflective

Information fusion

Op

tic

Mag

netic

Setup

Accuracy

…

Within

sam

e m

odalit

y

Information fusion

Different modality

Sensor response time

Our setup

LED

Sensor can

respond to

changes of

intensity of

lights

The Photoresistor (LDR)

Is it OK?

Photoresistor

A photoresistor is a

light controlled

resistor

From RPM to response time

𝑀𝑜𝑡𝑜𝑟 𝑠𝑝𝑒𝑒𝑑 = 6400 𝑟𝑝𝑚

1 𝑟𝑝𝑚 =60

6400𝑠𝑒𝑐𝑜𝑛𝑑

1 𝑟𝑝𝑚 𝑎𝑡 𝑙𝑒𝑎𝑠𝑡 2 𝑐ℎ𝑎𝑛𝑔𝑒𝑠

𝑠𝑒𝑛𝑠𝑜𝑟 𝑟𝑒𝑠𝑝𝑜𝑛𝑛𝑒 𝑡𝑖𝑚𝑒60

2∗6400

~ 4.7 ms

Even shorter in this case

Photoresistor vs photodiode

vs phototransistor

Phototransistor

A transistor which is sensitive to the

input light intensity

Operation similar to traditional

transistors;

Have collector, emitter, and base

Phototransistor base is a light-

sensitive collector-base junction

Dark Current: Small collector can

emit leakage current when

transistor is switched off.

Phototransistor

B

EC

Phototransistor

characteristics

B

E

C

Obstacle

Application Example:

Avoiding Obstacles

LED

Baffle

Phototransistor

From sensor to readable signals

Sensor

Changes in resistances,

current, etc.

Transform

Digital port:

0 (0v) or 1(5v)

Analog port:

0 (0v) ~ 1023 (5v)

Passive Sensor Readout Circuit

Photodiode Circuits

Passive Sensor Readout Circuit

Thermistor Half-Bridge

Passive Sensor Readout

Circuit

VCC

Wheatstone Bridge

Given an R1, how can I decide the

threshold?

Digital out

LDR

R1

The AD value will be here

Expose to light & Cover the

sensor, find min and max

Threshold = (max+min)/2

Question, if we can select R1?

5V

R1

RL

Vs

𝑉𝑠𝑙𝑜𝑤 =𝑅𝐿_𝑙𝑜𝑤

𝑅1 + 𝑅𝐿_𝑙𝑜𝑤

𝑉𝑠ℎ𝑖𝑔ℎ =𝑅𝐿_ℎ𝑖𝑔ℎ

𝑅1 + 𝑅𝐿_ℎ𝑖𝑔ℎ

0v

5v

How can we make this range

as large as possible?

If we change R1

1

𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛 𝑅1

=𝑉𝑠ℎ𝑖𝑔ℎ − 𝑉𝑠𝑙𝑜𝑤

=𝑅𝐿_ℎ𝑖𝑔ℎ

𝑅1 + 𝑅𝐿_ℎ𝑖𝑔ℎ−

𝑅𝐿_𝑙𝑜𝑤

𝑅1 + 𝑅𝐿_𝑙𝑜𝑤

A maple based solution

1

𝑑𝑓𝑢𝑛𝑐𝑡𝑖𝑜𝑛 𝑅1

𝑑𝑅1= 0

Setup

Reflective setup

Read out circuit

R2

+5V

GND

Vout

𝑉𝑜𝑢𝑡𝑚𝑎𝑥 = 5 −𝑚𝑖𝑛𝐴 ∗ 𝑅2

maxA

minA

𝑉𝑜𝑢𝑡𝑚𝑖𝑛 = max(0, 5 − 𝑚𝑎𝑥𝐴 ∗ 𝑅2)

The output

Microseconds

Volt

Vout_min

Vout_max

5 Digital port:

0 (0v) or 1(5v)

Analog port:

0 (0v) ~1023 (5v) analogRead() takes about 100 μs

digitalRead() takes about 1/16 μs

Digital signals

Understanding the digital Signal, what is 1, what is 0, what is rising, what is falling, what is change

VIL defines the maximum voltage level that will be interpreted as a 0 by a digital input. VIH defines the minimum voltage level that will be interpreted as a 1 by a digital input. VOL defines the guaranteed maximum voltage level that will appear on a digital output set to 0 . VOH defines the guaranteed minimum voltage level that will appear on a digital output set to 1 .

FALLING or

CHANGE

RISING or

CHANGE

Time 1 Time 2

Frequency = 1*10^6/(Time2-Time1))

Microseconds

Volt

This regionDigital 1


We can “blink” LED to simulate

signals

USBPWR

RESET3.3v5vGNDGNDVIN

A0A1A2A3A4A5

AREFGND

1312

~11~10

~98

7~6~5

4~3

2Tx> 1Rx< 0

PO

WER

AN

AL

OG

DIG

ITA

L (P

WM

~)

RESET

Ard

uin

o U

NO

ICSP

Photo transistor

R2R1

Vout

void loop() {

//blink LED to simulate 3000rpmdigitalWrite(8,HIGH);delay(10);digitalWrite(8,LOW);delay(10);

}

The real “drop” of LED

The real “drop” of LED

If we take 1.8 for red LED

𝑅1 =5 − 1.8

0.015≈ 220

USBPWR


A0A1A2A3A4A5

AREFGND

1312

~11~10

~98

7~6~5

4~3

2Tx> 1Rx< 0

PO

WER

AN

AL

OG

DIG

ITA

L (P

WM

~)

RESET

Ard

uin

o U

NO

ICSP

Photo transistor

R2R1

Vout

Can we connect Vout to digital

port

USBPWR


A0A1A2A3A4A5

AREFGND

1312

~11~10

~98

7~6~5

4~3

2Tx> 1Rx< 0

PO

WER

AN

AL

OG

DIG

ITA

L (P

WM

~)

RESET

Ard

uin

o U

NO

ICSP

Photo transistor

R2R1

Vout

?

Flow chart

Start

Initialization

Find time 1

RPM=10^6/(Tim2-Time1)*60

Find time 2

Blink the LEDMicroseconds

Volt

Vout_min

Vout_max

5

Time 1 Time 2

Read digital singals

Microseconds

Volt

Vout_min

Vout_max

5

Loop{

Val=digitalRead(port);

};

Time 1 Time 2

The frequency of

read (red lines)

depends on program

execution speed

Read digital singals

Microseconds

Volt

Vout_min

Vout_max

5

Loop{

Val=digitalRead(port);

};

We want to know?

Time 1 Time 2

The frequency of

read (red lines)

depends on program

execution speed

Digital signals

Understanding the digital Signal, what is 1, what is 0, what is rising, what is falling, what is change

VIL defines the maximum voltage level that will be interpreted as a 0 by a digital input. VIH defines the minimum voltage level that will be interpreted as a 1 by a digital input. VOL defines the guaranteed maximum voltage level that will appear on a digital output set to 0 . VOH defines the guaranteed minimum voltage level that will appear on a digital output set to 1 .

FALLING or

CHANGE

RISING or

CHANGE

Time 1 Time 2

Frequency = 1*10^6/(Time2-Time1))RPM=Frequency*60

Microseconds

Volt



Interrupts

In systems programming,

an interrupt is a signal to

the processor emitted by

hardware or software

indicating an event that

needs immediate

attention.

Interrupt

Interrupts

Start

Define Time1 and Time2 as variable

Find & Calculate RPMBased two adjacent

RISING time

Export RPM to serial port

Blink the LED

Interrupt

RISGING

Update

Time

RISGING

Update

Time

Time 1 Time 2 Microseconds

Volt

Using Interrupts in Arduino

On a standard Arduino board, two pins can

be used as interrupts:

Pin 2 = Interrupt 0

Pin 3 = Interrupt 1

Interrupt 1 Interrupt 0

Using Interrupts in Arduino

The interrupt is enabled through the following line:

attachInterrupt(interrupt, function, mode)

Example: attachInterrupt(0, rpm, RISING);

USBPWR


A0A1A2A3A4A5

AREFGND

1312

~11~10

~98

7~6~5

4~3

2Tx> 1Rx< 0

PO

WER

AN

AL

OG

DIG

ITA

L (P

WM

~)

RESET

Ard

uin

o U

NO

ICSP

Photo transistor

R2R1

Vout

Software

Start

Define Time1, Time2

Calculate RPMBased two adjacent

RISING time


Time1 = last rising time (microseconds)

Time2 = current RISING time

(microseconds)

Interrupt

Initialization, include defining

interrupt

RPM = 10^6/(Time2-Time1)*60

Blink the LED

Software

float rpmspeed;

unsigned long time1;


int ledPin=8;

void setup() {

//setup serial port

Serial.begin(9600);

//pin mode

pinMode(ledPin,OUTPUT);

//setup interrupt

attachInterrupt(0, rpm, RISING);

}

Start

Define Time1, Time2


RISING time




(microseconds)

Interrupt


interrupt

Blink the LED

Software

float rpmspeed;



int ledPin=8;

void setup() {

//setup serial port

Serial.begin(9600);

//pin mode


//setup interrupt


}

int - 2,147,483,648 to 2,147,483,647

Unsigned long - 0 to 4,294,967,295 (2^32 - 1)

float - 3.4028235E+38 and as low as -3.4028235E+38

Start

Define Time1, Time2


RISING time




(microseconds)

Interrupt


interrupt

Blink the LED

Software

// the loop routine

void loop() {

//calculate rpm

rpmspeed = 1000000.0 / (time2 – time1) * 60.0;

//export to serial port

Serial.println(rpmspeed);

//blink LED at 3000rpm, serial print and

//interrupt also take time

digitalWrite(8,HIGH);

delay(10);

digitalWrite(8,LOW);

delay(10);

}

Software

Start

Define Time1, Time2


RISING time




(microseconds)

Interrupt


interrupt

Blink the LED

// interrupt function record

// last two rising time

void rpm()

{

time1 = time2;

time2 = micros();

}

float rpmspeed;



int ledPin=8;

void setup() {

//setup serial port

Serial.begin(9600);

//pin mode


//setup interrupt


}

Software

micros(): get current time in microsecond unit . 1

second = 10^6 microsecond (µs)

rpmspeed = 1000000.0 / (time2 – time1) * 60.0

// interrupt function record

// last two rising time

void rpm()

{

time1 = time2;

time2 = micros();

}

RISGING

Update

Time

RISGING

Update

Time

Time 1 Time 2 Microseconds

Volt

Prototype

phototrasistor

123d.circuits.io

Workshops

03

Workshop

The E-Flite Blade 500 X BNF combines superior flight technology with ease of use. It comes pre-assembled and ready to fly right

out of the box, which means you can start making use of its incredible features almost immediately . It is an incredibly precise

machine that is highly responsive, which makes it a great option for beginners, as well as for more seasoned hobbyists who are

looking for a radio controlled helicopter capable of performing mesmerizing in-air stunts and maneuvers.

In the prototyping of the helicopter, it is important to identify the speed of the rotor. You are asked to prototype a system which is

able to detect the rotation speed of the rotor (It is about 3000RPM, The expected resolution is 1 RPM).

Attention:

In this workshop, we will use blink LED lights to simulate the reflection of the LED on a plate which is attached to the rotor.

The principle is: When the rotor rotates once, the reflected light will have a "bright and dark" cycle. In this exercise, we switch an

LED on and off to simulate this

e.g. 3000RPM

digitalWrite(ledPin, HIGH);

delay(10);

digitalWrite(ledPin,LOW);

delay(10);

Cas

e b

rie

f

10ms

ArchitectureA

nal

ysis

System

What types of information do we need?

A rotating motor

Simulated by LED blink

Arc

hit

ect

ure

of

the

pro

totp

ye

Sensor Controller

Photodiode Or phototransistor Arduino

3000 RPM = 50 Revolutions per second

1 RPM means = 1/50 second = 20 ms

halfRPMtoSecond is 20ms/2 = 10ms;

Thus

dealy(10);

Consider sensor reaction time

Enjoy

phototrasistor

Summary

04

Summary

Circuit, digital

signals, interrupt

Hardware & Software

Modality, Attribute,

Specifications

Sensor

Sensor

Thank you

Product Dynamics, L-E-2, Sensors

Io2022

Prof. Dr. Ir. J.M.P Geraedts

Dr. Y. Song, Martin Verwaal, Adrie Kooijman, Ir. Sander Minnoye

Faculty of Industrial Design Engineering

Delft University of Technology

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