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Optical Encoders


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To introduce basic knowledge of optical encoders and OPTEK product portfolio

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Optical Encoders

  1. 1. Optical Encoders <ul><li>Source: Grayhill Inc </li></ul>
  2. 2. Introduction <ul><li>Purpose </li></ul><ul><ul><li>An overview classification of Grayhill optical encoders </li></ul></ul><ul><li>Outline </li></ul><ul><ul><li>Working of optical encoders and parameters </li></ul></ul><ul><ul><li>Common characteristics of encoders </li></ul></ul><ul><ul><li>Human interface encoders, features and applications </li></ul></ul><ul><ul><li>General purpose optical encoders, features and application </li></ul></ul><ul><ul><li>Special function products, features and applications </li></ul></ul><ul><ul><li>Machine interface encoders, features and applications </li></ul></ul><ul><li>Content </li></ul><ul><ul><li>20 pages </li></ul></ul>
  3. 3. How Optical Encoders Work <ul><li>The photo detectors are special transistors that allow current to flow when the light from the LEDs is shining on them </li></ul><ul><li>Two LED-photo detector pairs are used, these produce the outputs A and B </li></ul><ul><li>The alternating on-off state produces the output signal </li></ul>LED Photo Detector Code Rotor LED Photo Detector Code Rotor Output A Output B OUTPUT A OUTPUT A OUTPUT B
  4. 4. Incremental / Absolute Encoders Indicates closed circuit, blank indicates open circuit Indicates closed circuit, blank indicates open circuit Incremental Encoder Absolute Encoder Quadrature 2-bit Code ¼ Cycle per Detent Code Position Output A B 1 2 ■ 3 ■ ■ 4 ■ 5 6 ■ 7 ■ ■ 8 ■ 9 10 ■ 11 ■ ■ 12 ■ 13 14 ■ 15 ■ ■ 16 ■ 4-bit Gray Code – 16 Position Code Position Output 1 2 4 8 1 2 ■ 3 ■ ■ 4 ■ 5 ■ ■ 6 ■ ■ ■ 7 ■ ■ 8 ■ 9 ■ ■ 10 ■ ■ ■ 11 ■ ■ ■ ■ 12 ■ ■ ■ 13 ■ ■ 14 ■ ■ ■ 15 ■ ■ 16 ■
  5. 5. Optical Encoders Parameters <ul><li>Pulses Per Revolution (PPR): The # of quadrature state changes per 360° rotation of the shaft </li></ul><ul><li>Cycles Per Revolution (CPR): The number of full quadrature cycles per 360° shaft rotation (four pulses per one cycle) </li></ul><ul><li>Resolution : The number of Pulses Per Revolution (PPRs) or Cycles Per Revolution (CPRs) in a specific encoder’s output For example: encoders with low PPRs (4-32) are “low resolution encoders” </li></ul>one cycle OUTPUT A OUTPUT A OUTPUT B ONE PULSE ONE PULSE ONE PULSE ONE PULSE POSITION 1 2 3 4 5 7 6
  6. 6. Common Characteristics of Encoders <ul><li>Long life </li></ul><ul><ul><li>1,000,000 to 300,000,000 cycle reliability, no mechanical contacts </li></ul></ul><ul><li>Require power source </li></ul><ul><ul><li>Typically at 5V </li></ul></ul><ul><ul><li>Can be customized (3.3V, 12V, 18V) </li></ul></ul><ul><li>Cable and connector options </li></ul><ul><li>Sealed versions available </li></ul><ul><li>Customizations available </li></ul><ul><ul><li>Shaft size / configuration </li></ul></ul><ul><ul><li>Detent / rotational feel </li></ul></ul><ul><ul><li>Terminations </li></ul></ul><ul><ul><li>Bushings </li></ul></ul><ul><ul><li>Output codes </li></ul></ul>
  7. 7. Human Interface Encoders <ul><li>Typical Features of Human Interface Encoders </li></ul><ul><li>Low Resolution: </li></ul><ul><ul><li>Specified in Pulses Per Revolution (PPRs) </li></ul></ul><ul><li>Detents: </li></ul><ul><ul><li>The place where the shaft “clicks” into position while rotated </li></ul></ul><ul><li>Pushbutton Feature </li></ul>
  8. 8. Human Interface Products <ul><li>Grayhill offers four general purpose optical encoders suitable for human interface applications </li></ul><ul><li>It includes 61B , 61C, 62A and 62S products </li></ul><ul><li>The 62S is the latest offering. It is the smallest package size encoder available </li></ul>
  9. 9. Human Interface Applications <ul><li>Medical applications: </li></ul><ul><ul><li>Ultrasound equipment, patient monitoring device </li></ul></ul><ul><ul><li>Defibrillators, X-ray equipment </li></ul></ul><ul><li>Automotive applications: </li></ul><ul><ul><li>Navigation systems climate controls </li></ul></ul><ul><li>Industrial application: </li></ul><ul><ul><li>Machine tools, process controls, factory automation </li></ul></ul><ul><li>Communication equipment, handheld tablets - voting machine, lab instruments, avionics </li></ul>
  10. 10. Advantages of Human Interface Encoder <ul><li>Compared to a mouse: </li></ul><ul><ul><li>An encoder can be mounted on the front panel of the device. This results in a self contained assembly that does not require additional space or surfaces for a mouse pad. </li></ul></ul><ul><li>Compared to keypads: </li></ul><ul><ul><li>Optical encoders require less panel space. </li></ul></ul><ul><ul><li>Operators do not have to look directly at the encoder while scrolling through menus or inputting data. </li></ul></ul><ul><li>Compared to potentiometers: </li></ul><ul><ul><li>Optical encoders output digital signals that are more compatible with today’s digital devices vs. the analog output of a potentiometer. </li></ul></ul><ul><li>Compared to trackballs: </li></ul><ul><ul><li>Optical encoders allow incorporation of “push to enter” pushbutton functionality. </li></ul></ul><ul><ul><li>Optical encoders resist collecting dust and are therefore lower maintenance than trackballs. </li></ul></ul>
  11. 11. General Purpose Optical Encoders <ul><li>Grayhill offers four general purpose optical encoders suitable for human interface applications </li></ul><ul><li>It includes 61B 61C, 62A and 62S products </li></ul><ul><li>The 62S is the latest offering. It is smallest package size encoder </li></ul>
  12. 12. Special Function Products <ul><li>Encoders with Joysticks - Series 60A and 60C: </li></ul><ul><li>The 60A and 60C joystick encoders incorporate an 8-way mechanical joystick </li></ul><ul><li>The 60C separates the pushbutton and joystick from the encoder on concentric shafts </li></ul><ul><li>The joystick provides added functionality in a single package </li></ul><ul><li>Its applications include automotive, avionics, commercial </li></ul><ul><li>Concentric Shaft Optical Encoders – Series 62C: </li></ul><ul><li>A concentric shaft encoder with a non-rotating inside shaft </li></ul><ul><ul><li>Insures against accidental actuation </li></ul></ul><ul><ul><li>Insures proper orientation of any legends printed on knob </li></ul></ul>
  13. 13. Special Function Products <ul><li>High Torque Family: </li></ul><ul><li>Products with high torque detent systems. </li></ul><ul><li>Required when application calls for positive tactile feedback. </li></ul><ul><ul><li>Avionics, pilots desire a positive detent feeling. </li></ul></ul><ul><li>Any application where an operator is likely to be wearing gloves. </li></ul><ul><li>These products require two to four times more rotational force to actuate compared to standard encoders. </li></ul>
  14. 14. Special Circuitry <ul><li>Low Power - 62V: </li></ul><ul><li>Operates at lower voltage (3.3V) </li></ul><ul><ul><li>Ideal for battery operated devices </li></ul></ul><ul><ul><li>Lower voltage also reduces risk in explosive environments </li></ul></ul><ul><li>Circuitry-Lighted Shaft-Series 62F : </li></ul><ul><li>An optical encoder with integrated LED and light pipe </li></ul><ul><li>Simplifies panel design </li></ul><ul><li>Redundant Circuits – 62R : </li></ul><ul><li>Ideal for critical applications </li></ul><ul><li>Target industries: Avionics </li></ul><ul><li>Originally designed for a helicopter ground avoidance system </li></ul><ul><li>62P Human Interface 16 Detent Positions </li></ul><ul><li>Introduced as a low price optical encoder to compete against low price mechanical encoders </li></ul><ul><li>Life: 500,000 cycles </li></ul>
  15. 15. Higher Resolution Encoders <ul><li>Grayhill offers three higher resolution encoders suitable for human interface applications </li></ul><ul><li>Ideal for human interface applications where fine adjustment, greater accuracy and smooth continuous rotational feel is required </li></ul><ul><li>61K and 61R encoders have 256 cycle per revolution product </li></ul><ul><li>Grayhill uses a special chip instead of photo detectors in 61S family in order to achieve the reduced package size </li></ul>
  16. 16. Applications of Higher Resolution Encoders <ul><li>Electric welding machines. </li></ul><ul><ul><li>Medical ventilator </li></ul></ul><ul><ul><li>Test equipment </li></ul></ul><ul><ul><li>Audio mixing consoles </li></ul></ul><ul><ul><li>High end amplifier </li></ul></ul>
  17. 17. Machine Interface Encoders <ul><li>Encoder is used as a feedback device in a motion control system. </li></ul><ul><li>Installed with moving equipment, not turned by hand. </li></ul><ul><ul><li>High resolution (specified in cycles per revolution). </li></ul></ul><ul><ul><li>No detents. </li></ul></ul><ul><ul><li>No push button feature. </li></ul></ul><ul><ul><li>May incorporate ball bearings to withstand high RPMs and shaft loads </li></ul></ul>
  18. 18. Machine Interface Encoders <ul><li>Series 63A: </li></ul><ul><ul><li>Absolute code output, 20mm package </li></ul></ul><ul><ul><li>256 Cycles Per Revolution (CPR), 8-bit code </li></ul></ul><ul><ul><li>Suitable when application requires discrete position detection at power-up </li></ul></ul><ul><li>Series 63Q </li></ul><ul><ul><li>20mm package </li></ul></ul><ul><ul><li>1024 Cycles Per Revolution (CPR). </li></ul></ul><ul><li>Series 63T </li></ul><ul><ul><li>Hollow shaft-mounts to end of motor or rotating shafts up to .375” </li></ul></ul><ul><ul><li>Metric sizes available </li></ul></ul><ul><ul><li>Up to 1024 Cycles Per Revolution (CPR) </li></ul></ul>
  19. 19. Applications of Machine Interface Encoders <ul><li>Motor shafts </li></ul><ul><li>Conveyor belts </li></ul><ul><li>Machine tools </li></ul><ul><li>Robots </li></ul><ul><li>Factory automation </li></ul><ul><li>Office printer / copier mechanisms </li></ul><ul><li>Antennas and telescopes </li></ul><ul><li>Elevators </li></ul><ul><li>Printing equipment </li></ul><ul><li>Smartcard fabricating equipment </li></ul>
  20. 20. Additional Resource <ul><li>For ordering Grayhill Optical Encoder, please click the part list or </li></ul><ul><li>Call our sales hotline </li></ul><ul><li>For more product information go to </li></ul><ul><ul><li>http:// </li></ul></ul><ul><li>Visit Element 14 to post your question </li></ul><ul><ul><li> </li></ul></ul><ul><li>For additional inquires contact our technical service hotline or even use our “Live Technical Chat” online facility </li></ul>