msa kemet webinar
TRANSCRIPT
MSA KEMET Webinar
KEMET SMD PIR sensing for proximity detectionMay 2020, Michael Freitag
SMD PIR sensing for proximity detection
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• What is infrared radiation and how can it be measured• Optical filtering and chassis material behavior• Demanding applications for PIR sensing• Gesture and human proximity sensing options• Sensor comparison & recommendation
What is infrared radiation ?
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• Oczillation and vibration of molecules emit IR from warm surfaces• IR waves are longer than visible light and represent temperature radiation• Photon´s emit to the ambient the higher the intensity the warmer the surface• IR radiates from a warm human body independently and is always present
Electromagnetic spectrum
How can IR be measured ?
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• IR waves are invisible for the human eyes but snakes have a 3D view of their ambient and can assemble an IR picture of a mouse in the dark
Intensity of „human body“ IR vs. wavelength
• A material need to be found to convert the energy of IR photons to electric energy
• Similar to a solar energy cell in a semi conductive material ions can be detected by a change of the energy level and its cause for electron movement as current between 2 opposite potentials
• Piezo ceramic material (PZT) has this ability
Pyroelectric effect of PZTOperation of Pyroelectric Infrared Sensor
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赤 外 線
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焦電材料
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赤 外 線
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① No infrared ② Infrared comes in ③ Infrared stable ④ Infrared cut off ① No infrared
① ② ③ ④ ①
Time
Sens
or o
utpu
t vol
tagePyroelectric
sensorPyroelectricelement JFET
R
GD
S
2~15V
Infrared Infrared
Pyroelectricmaterial
• When IR photons become present electrons move to a higher energy level
• While IR is present no current flows / no movement
• Once photons fade off the electrons move to opposite direction
• Changing IR situations will generate signals movement can be detected
Optical filtering for signal robustness
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• To avoid influences like sunlight an optical low pass filter is helpful in front of the sensor
• The sensing elements of PZT determine by design the maximum length of the waves
• A bandpass results of 3 to 5.5µm and focuses on an area of proper detection
• With less expected disturbances the sensitivity and gain of sensing can be increased LP Filter
Limit of PZT may varyFocus range
Sunlight
IR Transmission by material & thickness
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• Chassis material of a control device can be kept plain when sensing with a high gain through it even when the material between the sensor and the IR „object“ filters quite significantly
1mm thicknessand detectance
distance
Based on SS-430Testboard
-100-90-80-70-60-50-40-30-20-10
0
0 1 2 3 4 5 6
Chan
ge o
f Sen
sor
outp
ut v
olta
ge[%
]
HDPE plate thickness [㎜]
HDPE / Color: transparent
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0102030405060708090
100
2 3 4 5 6 7 8 9 10 11 12 13 14
Tran
smitt
ance
[%]
wavelength [um]
Optical filter
HDPE/Thickness 1.0㎜HDPE/Thickness 2.0㎜
0102030405060708090
100
2 3 4 5 6 7 8 9 10 11 12 13 14
Tran
smitt
ance
[%]
wavelength [um]
Optical filter
Glass/Thickness 0.5㎜
Glass/Thickness 1.0㎜
0102030405060708090
100
2 3 4 5 6 7 8 9 10 11 12 13 14
Tran
smitt
ance
[%]
wavelength [um]
Optical filter
ABS/Thickness 1.0㎜
0102030405060708090
100
2 3 4 5 6 7 8 9 10 11 12 13 14
Tran
smitt
ance
[%]
wavelength [um]
Optical filter
Acrylic/Thickness 0.5㎜Acrylic/Thickness 1.0㎜
IR Transmission by material & thickness
Temperature difference ∆T
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• Once the temperature difference of the ambient to the object shrinks detection becomes less sensitive
• Let´s assume the 37°C body temperature as constant then a difference of 2°C is the absolute minimum for detection
• In most applications more that 5°C should be considered to operate reliable (up to 32°C)
Tempered glasst = 3.2mm
Sensor chassis
0.0
0.5
1.0
1.5
2.0
2.5
0 5 10 15 20 25 30 35 40 45O
utpu
t-V
[V0-
p]
Detection distance [cm]
Example : Tempered glass = 3.2mm Clear
閾値⊿T=10℃⊿T=8℃⊿T=5℃
Detection
Non Detection
threshold
Application
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• Gesture sensing (short distance)
o Smart home environment
o Medical ambient to avoid surface contact and contamination
o Wake up from energy saving modes
• Human proximity (long distance)
o Energy saving for screens, projectors & airconditioning systems
o Silent alarms & action on approach functionality
o Preparation function to leave deep sleep of equipment prior to usage
Application Example
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Study Robot
Hello
Turn on when people approach.Turn off when people leave.
Sensor
Portable Projector
Business Phone
Sensor
Office security system
Video Intercom
SensorAnnounce information when people approach
Sensor
Rice Cooker
LED button display whenpeople approach
Sensor
alarm
Non-Contact Card Key
Turn on card reader when people approach
Adapted in Market
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Gesture detection
directional Proximityyes/no
10~20cmChassis surface(Resin, glass)
SensorSensor
HDPEt=1mm
SensorHDPEt=3mm
Detection distance changes
PL-N series
SS-430evaluation
QMS-EA0 series
QMS-Mevaluation
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2x2 Array
DigitalI2C
Fullanalog
QMS-EA2 series
QMS-Mevaluation
PIR sensor guidanceGesture sensing up to ~1m
Directional sensing
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• Having multiple sensors acting independent adds directional information
• Horizontal & vertical gestures allow a set of 4 cases as movement information
Movement
L R
Movement
R L
How to extend the detection range ?
14Unit: m Unit: m
Horizontal view Vertical view
±37° [74° full angle] ±28° [56° full angle]
Unit: m
lens
Projection view@5m distance
• Similar to streamline photons to the detective area lenses can be used to extend a detection range
• To keep a maximum overall sensitive angle a matrix of detective areas is build up and channels the IR
Detection angle adjustment in a nutshell w/o lens
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ABS(t=3mm~)
Cover (High density polyethylene)
Sensor
CaseAperture size(mm)
Sensor distance(mm) Cover(HDPE)
θ
0
2
4
6
8
10
12
14
16
18
20
0 2 4 6 8 10 12
Aper
ture
size
(mm
)
Sensor distance (mm)
Horizontal
60°
55°
50°
45°
40°
35°
30°
25°
20°
15°0
2
4
6
8
10
12
14
16
18
20
0 2 4 6 8 10 12
Aper
ture
size
(mm
)
Sensor distance (mm)
Vertical
60°
55°
50°
45°
40°
35°
30°
25°
20°
15°
Full sensor angle
The individual datasheetspecifies the aperturesize and distance from sensor surface
PIR line comparisonin common SMD & small size
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QMS advantages QMS disadvantages PL advantages PL disadvantages
Direction detection optional by 2x2 array
Without lens ≤20cm detection range
Up to 2m detection without lens (HDPE)
Needs initially 30 sec for warm up
I2C communication & programmable gain
High speed detection compromises sunlight
Analog signal for own algorithmic integration
Very quick gestures not detectable
3 different standard setups available
Typically 22µA (normal)3.5µA (low power mode)
Sensor consumes 1nA, no standby is needed
Immediate function after switching on
Low current consumption circuit proposal (3.5µA)
Testboard QMS-M available
Sensor board for easy integration (SS-430/431)
Very quick detection based on low mass PZT
Best competitive operation with sunlightUp to 5m range with
fresnel flat lens in 3 color
Datasheets, supporting documents & samplesPL series, analog, high sensivity
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Gesture short range Proximity long range [5m]
Sensor Sensor
TestBoard
TestBoard
TestBoard
TestBoard
Lens
Lens
Lens
Datasheets, supporting documents & samplesUSEQMS series, digital, high sensivity
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Single sensor Sensor array 2x2
Sensor
Module
KITMotion
detection
Maximumrange
Mediumrange
Withoutlens
Withlens
Withlens
Withlens
Sensor parameter comparison
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• Communication: I2C – digital• View-angle: >90°/~60°(small aperture)• Size: 5.65 x 3.7mm h=1.55mm• Supply voltage: 1.75 … 3.60 VDC
• Operating Temperature: -40…85°C• Weight: 0.07g• Current consumption: 22µA (normal
mode) / 3.5µA (low power mode)
• Communication: JFET - analog• View-angle: 120°/74° (x-with lens)• Size: 4.8 x 5mm h=1.7mm• Supply voltage: 2.0 … 15 VDC
• Operating Temperature: -40…70°C• Weight: 0.1g• Current consumption: 1nA
USEQMS PL-N / PL-Q
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Conclusion & questions- PIR sensors limit bandwidth range to act more reliable- Depending the application different sensors are available- Evaluation boards can be used as „easy implementation“- Proximity or gesture sensing is possible for automation