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

©KEMET Corporation. All Rights Reserved. 15Sensor Sensor

ABS(t=3mm～)

Cover (High density polyethylene)

Sensor

CaseAperture size(mm)

Sensor distance(mm) Cover（HDPE）

θ

0

2

4

6

8

10

12

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Aper

ture

size

(mm

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Sensor distance (mm)

Horizontal

60°

55°

50°

45°

40°

35°

30°

25°

20°

15°0

2

4

6

8

10

12

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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