CMPE 118 MECHATRONICS Introduction to Sensors Or, How the world gets into our programs

CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS

Introduction to Sensors

Or,

How the world gets into our programs


Mechatronic Systems

DecisionMaking

Actuation

Worldto

Signal

The World

MicroController


The World to Signal

Sensors or Transducers

Convert one physical phenomenon to another

Examples that you Encounter Daily

Signal Conditioning

Match sensor output to the microcontroller’s input



+

- CharacteristicsInfinte GainDraws No Input Current

Operational Amplifier


+

- R1

R2

A

B

Vout Vin

Inverting Amplifier

Vout

R2 R1

-Vin =

Vout

Vin

R2

R1 = -


+

- R1

R2

A

B

Vout

Vin

Non-Inverting Amplifier

= Vin R1

Vout R1 + R2

= Vin R1

Vout R2 1 +


What can the Microcontroller Measure ?

Hint: Only 2 things

TimeEvery Microcontroller can measure the passage of time

If necessary purely with software

VoltageMicrocontrollers with an Analog to Digital converter (A/D)


What can the Microcontroller Measure ?


Basic Sensors: Light

PhotoCells

CdS Resistance Varies with Incident LightMore Light = Lower Resistance

Spectral Response

Approximates Human Eye

Dynamic Response

Power Rating


CdS Photocell Specifications

Opto-semiconductors: CdS Photoconductive CellsThese cells h ave a sp ectral resp on se c lose to the h um an eye.

T y p e N o . P a c k a ge ( m m )

PeakS en s itiv it y

W a v e le n g thp

( n m )

R e s is ta nc e

* 4 R is e T im e

t r0 t o 6 3 %

1 0 l x(m s )

F a ll T im e tf

1 0 0 t o 3 7 %10 l x(m s )

1 0 l x *2

M in . M a x. ( k )

0 lx * 3 M in .

(M )

P 1 1 1 4 - 0 4

M e t a l

T O - 1 8 5 7 0 1 5 t o 4 5 10 0 . 8 0 40 20

P 3 2 0

5 .5

5 2 0 3 5 t o 1 0 0 20 0 . 8 5 60 20

P 5 5 9 5 4 0 2 .9 t o 8 .5 0 .1 0 . 6 0 1 0 0 1 4 0

P 9 3 0 5 6 0 7 t o 2 3 0 .5 0 . 6 860

90

P 1 4 6 5 5 2 0 2 7 t o 8 1 10 0 . 8 5 20

* 1 : D ua l e lement co a ting typ e . Listed d a ta a re fo r o ne e lement.* 2 : M e asure d with a tungsten la mp o f 2 8 5 6 K .* 3 : M e a sure d 1 0 se c o nd s a fte r re mo va l o f inc id e nt illumina te io n o f 1 0 /x

* 4: G a mma c ha ra c te r is tic s b e tw e e n 1 0 lx a nd 1 0 0 l x.R 1 0 , R 1 0 0: C e ll re sista nc e va lues a t 1 0 l x a nd 1 0 0 l x. Ga mma c ha rac te r is tic s varia tio ns o f 0 .1 0 .

1001 0 = log(R10/R100)

log(100/10)


CdS Photocells: How do you use them?

In a voltage divider to generate a voltage

R210k

5V

R1

R210k

Anywhere you can use a resistor to vary a circuit’s output

Does that suggest another possible circuit?


How else could you use a Photocell?



Photo-Transistors

NPN only

Light Replaces the base current

Spectral Response

Dynamic Response

Spectral sensitivity characteristics100

80

60

40

20

Wavelength (n m)700 800 900 1000 1100 1200

0600

VCE = 10V


0° 10° 20°

30°

40°

50°

60°

70°80°90°

Directivity characteristics

20

90

100

80

70

60

50

40

30 Rela

tive

sens

itivi

ty S

(%)

Directional Characteristics

Sensitivity/Linearity

I CE(L) — L

Illuminance L (lx)

Colle

ctor

pho

to c

urre

nt

ICE

(L)

(m

A)

VCE = 10VTa = 25°CT = 2856K

10 3

10 2

10

1

10 –1

10 10 3 10 410 210 –21


LTR3208EData Sheet



Phototransistors: How Do You Use Them?

5V

R11k

Q1

5V

R11k

Q1

Simple Ways


Phototransistors: How Do You Use Them?Better Way

R110k

5V

R110k


Basic Sensors: Magnetic Field

• Simplest: Reed Switch


Basic Sensors: Magnetic Field

Hall Sensors

Semiconductors

Switches

Analog


Uni-Polar

BiPolar

Linear


Linear Output SensorMeasuring Rotation

Digital Output SensorUsing Bias Magnet


Measuring Position

Translate Movement to ??? To Voltage

What are examples of ???


Optical Sensors for Position

Reflective


Optical Sensors for Position

Transmissive


Encoders For Position Sensing

Combine the TransmissiveOptical Sensor

With a rotating Mask


Encoder: How it works

Quadrature


Encoders: Where Do You Find Them?

Printers

Disk Drives


Basic Sensors: TemperatureThermistors

Large R for T

Non-Linear

But well understood

Temperature Sensitive Resistor


Basic Sensors: Temperature

Platinuum Restive Temperature Devices

RTDs

Wide Temperature Range

Extremely Linear

Very Stable

Not Very Sensitive


• AVAILABLE IN 100, 500, 1000, AND 2000 OHM RESISTANCE VALUES

• STANDARD IEC 751, ASTME1137 & NON-STANDARDTOLERANCES AVAILABLE

• WIDE CHOICE OF SIZES• 2, 3, AND 4 WIRE EXTENSION LEADS AVAILABLE• CUSTOM-ENGINEERED TEMPERATURE PROBE

ASSEMBLIES

PLATINUM THIN F ILM RTD ELEM ENTS

Sens or Scien tific, Inc. Platinum Thin Film RTD Elem en ts are fabricat -ed using s tate-of-the-art th in film process ing techniques , res ulting inan elem ent of exceptional quality and s tability. The wide choice ofres is tance, tolerance , and s ize options a llows for com plete des ignflexibility.RTD elem en ts a re ava ilab le w ith extens ion leads , and inco rporated incom plete tem perature probe as sem blies . P leas e contact Sens o rScientific for additional inform ation.Assem blies: Generally, th in film RTD elem ents are incorporated into som e type ofas sem b ly for p ro tection . Extens ion leads m ay be attached via so lder -ing, crim ping, brazing or welding. The attachm ent m ethod m ust becapable of w iths tanding the intended m axim um operating tem perature.The following precautions m us t be taken when incorporating theelem ent into an as sem bly:1 ) Avoid s tra in ing the elem ent leads .2) If extens ion leads are attached via s oldering or brazing, all flux

res idue m us t be rem oved.3) The res is tance of extens ion leads m us t be taken in to cons idera tion.

Res is tance value at 0 °C ca librated 1m m from end o f lead wire . 4) If e lem ents are encaps ulated in a potting com pound, insure that

the com pound will not induce pres sure loads, res ulting in a strain-gage effect.


Resis tance L W H at 0 Deg. C. Length Width Height Part Num ber

ohms mm mm mm100 5.0 +/- 0 .2 1.0 +/- 0 .2 1.3 +/- 0.2 P01 lln 1100 5.0 +/- 0 .2 1.5 +/- 0 .2 1.3 +/- 0.2 P01 lln 2100 2.3 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P01 lln 3100 5.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P01 lln 4100 10.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P01 lln 5100 5.0 +/- 0 .2 4.0 +/- 0 .2 1.3 +/- 0.2 P01 lln 6100 1.6+/- 0 .15 1.25 +/- 0.1 1.00 +/- 0 .2 P01 ll M7500 5.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P05 lln 1500 10.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P05 lln 2500 5.0 +/- 0 .2 4.0 +/- 0 .2 1.3 +/- 0.2 P05 lln 3

1000 4.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P10 lln 11000 10.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P10 lln 21000 5.0 +/- 0 .2 4.0 +/- 0 .2 1.3 +/- 0.2 P10 lln 31000 1.6+/- 0 .15 1.25 +/- 0.1 1.00 +/- 0 .2 P10 ll M42000 10.0 +/- 0 .2 2.0 +/- 0 .2 1.3 +/- 0.2 P20 lln 4

ll - To leranc e 0B = D IN B n - Te m p era tu re R a nge01=1/10 D IN B at 0°C 05 = ASTM B L = -50 to + 400 D eg C02 = 1/5 D IN B at 0°C 06 = 3/2 D IN B at 0°C M= -50 to + 550 D eg C03 = 1/4 D IN B at 0°C 07 = 2 D IN B at 0°C H = -50 to + 600 D eg C04 = 1/3 D IN B at 0°C 08 = 5 D IN B at 0°C0A = 1/2 D IN B (D IN A) at 0°C 09 = 10 D IN B at 0°C

R es is tanc e v a lue at 0 °C calibrated 1m m f rom end oflead wire. D IN = IEC 751

Limited Range of Resistances

R proportional to R at 0C



Photo-Diodes

Spectral Sensitivity

Speed

Light Sensitivity


Wide Dynamic Range



LTR516ADData Sheet


Photodiodes: how Do You Use Them?

D1

R1100k

Documents

CMPE 118 MECHATRONICS Introduction to Sensors Or, How the world gets into our programs