5.1.2 Explain the Proximity sensors

5.1.2 Explain the Proximity sensors

•       Widely used in general industrial automation

      – Conveyor lines (counting,jam detection, etc)

      – Machine tools (safety interlock, sequencing)

•       Usually digital (on/off) sensors detecting the presence or absence of an object

 

•        Consist of:

     – Sensor head: Mechanical, optical, inductive, capacitive

     – Detector circuit

     – Amplifier

     –       Output circuit: TTL, solid state relay

 (source: http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf )

  

Mechanical Proximity Sensor /limit switch

•       Essentially a mechanical switch

•       On/off operation only

•       Two general modes

        – Normally Open (NO)

        – Normally Closed (NC)

•       Come in a wide variety of mechanical forms

 

•        For a wide range of uses

EXAMPLES : MECHANICAL PROXIMITY SENSORS

http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf

OTHER TYPES OF PROXIMITY SENSORS

•       Ultrasonic Proximity Sensors

–      Use sound pulses

–      Measures amplitude and time of flight

–      Range provides more than on/off information

–      Frequencies 40KHz-2MHz

http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf

INDUCTIVE SENSOR

•       Inductive and Capacitive Proximity Sensors

–      Inductive sensors use change in local magnetic field to detect presence of metal target

CAPASITIVE SENSOR

–      Capacitive Sensors use change in local capacitance caused by non-metallic objects

–      Generally short ranges only

–      Regarded as very robust and reliable

http://ee.sharif.edu/~industrialcontrol/Summary_Automation_Sensors_tutorial.pdf

VIDEO: MAKING YOUR OWN PROXIMITY SENSOR USING LED!!!