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Proximity Sensors. Team 10. Facilitator- Dr. Wen Li Nolan Boyda Mark Holzhauer Jared Jones Eric Martz Justin Walz. Overview. Importance of Proximity Sensors Applications Common types Inductive Proximity Sensors Capacitive Proximity Sensors Resistive Proximity Sensors

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team 10

Proximity Sensors

Team 10

Facilitator- Dr. Wen Li

Nolan Boyda

Mark Holzhauer

Jared Jones

Eric Martz

Justin Walz

overview
Overview
  • Importance of Proximity Sensors
  • Applications
  • Common types
  • Inductive Proximity Sensors
  • Capacitive Proximity Sensors
  • Resistive Proximity Sensors
  • Analog/Digital Configuration
  • Interfacing with PLC
  • Our choice
  • Conclusion
what is a proximity sensor
What is a Proximity Sensor?
  • A device that uses various methods to measure a relative distance.
  • Outputs the distance as an electrical signal.

http://www.omron-ap.com/product_info/E2EM/e2em_proximity_sensor.jpg

why use proximity sensors
Why Use Proximity Sensors?
  • Can detect objects with or without making direct contact
  • Extremely accurate measurements
  • Very fast measurements
  • Interface with Programmable Logic Controller
  • Robust
    • Long lifetime due to absence of mechanical parts
    • Large temperature range
    • Operate in contaminated environments
common proximity sensors
Common Proximity Sensors
  • Inductive
  • Capacitive
  • Resistive
  • Infrared
  • Sonar
slide6

Inductive Proximity Sensors

Components of inductive sensor

Probe that uses oscillating LC circuit to sense changes in distance to the target

Driver electronics to convert amplitude changes to steady-state DC signal

Device that correlates DC signal to distance

How inductance relates to distance

http://image.made-in-china.com/2f0j00wvNtOlqKwbor/M18-Inductive-Proximity-Sensor-Proximity-Switch-IBEST-.jpg

slide7

Inductive Proximity Sensors

Internal Circuit

Oscillator: Causes a pulsating magnetic field around the coil which is near the sensor head. Eddy currents circulate within target decreasing oscillator amplitude.

Demodulator : Acts as a positive peak detector to obtain a steady DC voltage from a sine wave input.

SchmidtTrigger : Forces rapid transitions between low and high voltage inputs

Output: Provides 0V to load when low, or a specific voltage correlating to the target distance when high.

http://www.claytonengineering.com/Training/myweb6/Sensors/F_Ind&Cap_Ss.pdf

http://www.wisc-online.com/objects/ViewObject.aspx?ID=IAU5207

slide8

Inductive Proximity Sensors

Advantages

No physical contact with objects

Fast response

Very robust (can be fully encapsulated in resin)

No moving parts (long life)

Disadvantages

Limited range

Material must be electrically conductive

Applications

Metal detectors

Traffic lights

Automatic car wash

capacitive proximity sensors
Capacitive Proximity Sensors
  • Three basic components
    • Probe that uses capacitance to sense changes in distance to the target
    • Driver electronics to convert capacitance changes into voltage changes
    • Device to indicate and/or record the resulting voltage change
  • How capacitance relates to distance
    • Size of plates
    • Gap Size
    • Dielectric material (material between plates)
    • For ordinary sensing, only gap size is variable

http://www.automationdirect.com/adc/Overview/Catalog/Sensors_-z-_Encoders/Capacitive_Proximity_Sensors

capacitive proximity sensors1
Capacitive Proximity Sensors
  • Internal Circuit
    • Oscillator that causes a pulsating electric field from the sensor head. Voltage change observed when target present.
    • Demodulator that acts as a positive peak detector to obtain a steady DC voltage from a sine wave input.
    • SchmidtTriggerthat forces rapid transitions between low and high voltage inputs
    • Output that provides 0V to load when low, or a specific voltage correlating to gap distance when high

http://www.wisc-online.com/objects/ViewObject.aspx?ID=IAU5207

capacitive proximity sensors2
Capacitive Proximity Sensors
  • Advantages
    • Unaffected by dust or opaque containers
    • Higher resolutions (often sub-nanometer)
    • Inexpensive
    • Not sensitive to material changes
      • Responds to all conductors equally
    • Can measure non-conductors as well
  • Disadvantages
    • Slower than other sensors (100 µsec)
    • Not good in dirty or wet environments
    • Challenging output conditioning
  • Applications
    • Many displacement measurement applications
    • Bulk-handling machines, level detectors, package detection
resistive proximity sensor
Resistive Proximity Sensor
  • How they work
    • Object pushes against shaft
    • Wiper moves across resistive element to create voltage divider
    • Creates an analog signal that can be used directly or can be digitized

http://www.ahmetozkurt.net/MEC515/week2_%20displacement.pdf

http://www.ahmetozkurt.net/MEC515/week2_%20displacement.pdf

resistive proximity sensor1
Resistive Proximity Sensor
  • Sensor components
    • Resistive element
      • Wire-wound
      • Conductive plastic
      • Hybrid
    • Taper
      • Linear
      • Logarithmic
      • Sine

www.directindustry.com

http://www.ahmetozkurt.net/MEC515/week2_%20displacement.pdf

resistive proximity sensor2
Resistive Proximity Sensor
  • How they are chosen
    • Electrical Loading
      • Potentiometer resistance must be higher if the part being measured has lower resistiance
    • Life
      • Mechanical movement wares down the sensor over time
      • Sensor needs to be chosen based on acceptable life span
resistive proximity sensor3
Resistive Proximity Sensor
  • Examples

www.machinedesign.com

www.Ecbub.com

resistive proximity sensor4
Resistive Proximity Sensor
  • Advantages
    • Cheap
    • Simple
    • Adaptable
  • Disadvantages
    • Object must make contact with sensor
    • Moving parts decrease sensor life
  • Applications
    • Touchscreens
    • Potentiometers
the project
… The Project

Digital Proximity Sensors (Induction)

Analog Proximity Sensors (Induction)

Automation Direct: AE9-10-1A

Sensing Distance: 0-4mm Analog Signal

Used in:

Total length of part

Inside diameter of part

Depth of hole

Automation Direct: AE1-AP-1F

  • Sensing Distance: 1.5mm nominal sensing distance
  • Used in:
    • Part present at start
    • Servo slide forward
    • Servo slide reverse
digital proximity sensors how to wire
Digital Proximity Sensors: How to Wire
  • 8mm diameter
  • 10-30 Volt DC power
  • 3-wire
  • PNP transistor
  • Cable is shielded (quick connect)
  • 1.5mm nominal sensing distance
  • Normally open output
analog proximity sensors how to wire
Analog Proximity Sensors: How to Wire
  • 8mm diameter
  • 10-30 Volt DC power
  • 3-wire
  • 0-10 Volt DC analog output
  • 2 meter attached cable is shielded
  • 0-4mm sensing distance
what we have to play with so far
What we have to play with so far...
  • Analog proximity sensor holder for total length
    • Protective housing
    • Exact measurements
      • .001% accuracy
what the plc sees analog prox
What the PLC sees (analog prox)
  • Comes in as analog signal
  • Resolution of analog input card (Allen Bradley 1762-IF4)
    • -1 = 32,767
  • Needs to be scaled to inches (sensing distance)
  • Tricky equation:
    • Scaled output=(scaled max-scaled min)/(input max-input min)+scaled min-[input min*(scaled max-scaled min)/(input max-input min)]
      • Y = mx+b
what the plc sends to hmi
What the PLC sends to HMI
  • Can use offset value
    • Add value to F10:9 and move to new F (F10:4)
  • HMI reads F10:4 value
    • This value is total length of part
what the operator sees
What the operator sees
  • Appearance of the touchscreen
conclusion
Conclusion
  • Why we chose inductive sensors?
    • Capacitive do not work well in oily environments
    • Resistive require direct contact