cmpe 118 mechatronics introduction to sensors or, how the world gets into our programs
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CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Introduction to Sensors
Or,
How the world gets into our programs
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Mechatronic Systems
DecisionMaking
Actuation
Worldto
Signal
The World
MicroController
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
+
- CharacteristicsInfinte GainDraws No Input Current
Operational Amplifier
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
+
- R1
R2
A
B
Vout Vin
Inverting Amplifier
Vout
R2 R1
-Vin =
Vout
Vin
R2
R1 = -
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
+
- R1
R2
A
B
Vout
Vin
Non-Inverting Amplifier
= Vin R1
Vout R1 + R2
= Vin R1
Vout R2 1 +
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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)
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: Light
PhotoCells
CdS Resistance Varies with Incident LightMore Light = Lower Resistance
Spectral Response
Approximates Human Eye
Dynamic Response
Power Rating
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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)
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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?
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: Light
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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Phototransistors: How Do You Use Them?
5V
R11k
Q1
5V
R11k
Q1
Simple Ways
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Phototransistors: How Do You Use Them?Better Way
R110k
5V
R110k
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: Magnetic Field
Hall Sensors
Semiconductors
Switches
Analog
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Linear Output SensorMeasuring Rotation
Digital Output SensorUsing Bias Magnet
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Measuring Position
Translate Movement to ??? To Voltage
What are examples of ???
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Encoders For Position Sensing
Combine the TransmissiveOptical Sensor
With a rotating Mask
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: TemperatureThermistors
Large R for T
Non-Linear
But well understood
Temperature Sensitive Resistor
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: Temperature
Platinuum Restive Temperature Devices
RTDs
Wide Temperature Range
Extremely Linear
Very Stable
Not Very Sensitive
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
• 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.
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
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
CMPE 118 MECHATRONICSCMPE 118 MECHATRONICS
Basic Sensors: Light
Photo-Diodes
Spectral Sensitivity
Speed
Light Sensitivity