03 - Actuators and Sensors

1. 03 - Actuators and Sensors

2. The intent of this presentation is to present enough information to provide the reader with a fundamental knowledge of actuators and sensors used within Michelin and to better understand basic system and equipment operations.

3. Actuators and Sensors This Presentation consists of six modules. The following is a brief description of the information presented in each module. Module 1 – Pushbuttons Module 2 – Limit Switches Module 3 – Inductive Proximity Detectors Module 4 – Ultrasonic Proximity Detectors Module 5 – Capacitive Proximity Detectors Module 6 – Photo Detectors Appendix – Terms and Definitions

4. Module 1: Push Buttons Module 1 Push Buttons

5. Module 1: Push Buttons Pushbutton Control Stations A pushbutton station is a device that can provide control of a motor with the pressing of the appropriate pushbutton. With pushbutton stations a motor can be controlled from any one of several locations while only using one magnetic starter. The start, forward, reverse, fast, slow and stop operations of a motor may be controlled by pushbuttons. Auxiliary pushbuttons are used to control the motor from remote points. The auxiliary control may be a simple stop or start pushbutton or the same controls as the main station. Industrial pushbuttons are used in control circuits to actuate magnetic contactors or remote-operated controllers which handle power circuits. Pushbuttons are pilot devices and must be ruggedly constructed to withstand operator and mechanical abuse. They are frequently exposed to oils, coolants, chemicals, dusts, and various foreign elements. Heavy electrical loads are sometimes carried by the contacts of the pushbutton because of the high inrush current drawn by larger contactors. Pushbuttons are classified as standard-duty or heavy-duty, according to their current handling capabilities. Heavy-duty oil tight, and multi-light-control oil-tight are classified according to their ability to withstand these conditions. The terms standard-duty and heavy-duty describe only the contact capacity of the pushbutton in its making and breaking ability. These designations have no reference to the service conditions or frequency of operation.

6. Module 1: Push Buttons Standard Duty Pushbuttons Most systems use standard duty pushbutton stations to control A-C or D-C starters. General-purpose pushbutton stations are designed for operating flexibility and ease of wiring. Padlocking attachments are sometimes added to the pushbutton stations. These padlocking attachments are added to lock the "stop" button in the depressed position. Single Contact Ratings Standard-duty units have contacts rated for pilot duty, typically as follows: AC 3.0 Amperes, 120 volts 1.5 Amperes, 240 volts 0.75 Ampere, 480 volts 0.6 Ampere, 600 volts

7. Module 1: Push Buttons Heavy Duty Pushbuttons Heavy-duty pushbutton stations are found in many industrial applications. They have approximately twice the current rating of the standard-duty station. They come with any combination of pushbuttons, selector switches, jogging buttons, and pilot lights. Pushbuttons are available with flush, extended, or mushroom heads. They may have either momentary or maintained contacts. Heavy-duty pushbutton units have double-break contacts rated for pilot duty, typically as follows: ACDC 6 Amps, 120 Volts1.1 Amps, 120 Volts 3 Amps, 240 Volts 0.55 Amps, 230 Volts 1.5 Amps, 480 Volts 0.2 Amps, 550 Volts 1.2 Amps, 600 Volts

8. Module 1: Push Buttons Pushbutton Station Descriptions General-purposestations have steel bases and steel wraparound covers that fit tightly to exclude dirt and dust, as illustrated below. Watertight and dust tight stations have a stainless steel enclosure with a gasket between the cover and base. Water tight, corrosion-resistant stations are intended for applications where they are subject to corrosive fumes or liquids. The enclosure is made of nonmetallic material, and synthetic rubber boots protects the pushbuttons. This is illustrated below.

9. Module 1: Push Buttons Pushbutton Station Descriptions Pushbutton stations for hazardous locations are suitable for hazardous gas and hazardous dust locations. A machined surface is provided between the cover and base. Oil tight pushbutton control stations are used wherever there is presence of oil, coolant, and other non-corrosive industrial liquids. These control stations may be the surface mounted, flush mounted or pendant types. These stations have an enclosure that is sealed with a neoprene gasket. One or more neoprene washers tightly seal individual oil tight units. All these control units may include momentary or maintained contact pushbuttons. The contacts are usually the double-break type. These contact blocks can be assembled in numerous contact arrangements.

10. Module 1: Push Buttons Pushbutton Station Descriptions Single and double circuit constructed contact blocks are frequently used in any combination of "normally open" or "normally closed" circuits. Double circuit blocks have an individually operated contact plunger for each circuit made from high strength phenolic to resist cracking and warping. Several contact blocks can be stacked behind the pushbutton operator, as illustrated below. Each unit usually consists of two parts, the operator and the contact block. The bodies of the operators are die-castings, the operating buttons are molded plastic, and the locking rings are usually aluminum. One or more synthetic rubber washers provide the oil tight seal between the panel and operator.

11. Module 1: Push Buttons Pushbutton Station Descriptions Accessories Some types of pushbutton stations may be supplied with a padlocking attachment that locks the stop button in the depressed position. Some pushbutton stations may have pilot lights on them that indicate their particular function. Pushbutton stations usually use mushroom heads as an E-stop button.

12. Module 1: Push Buttons Pushbutton Station Descriptions Pushbutton Operators Different types of pushbutton and cylinder lock operators are used. Some of these are flush button, extended button, mushroom head, and jumbo mushroom head. The buttons are a solid color usually made of molded plastic. The cylinder lock type pushbutton can be locked in various positions and the key can be removed from the lock. A keyhole "dust cover" prevents dirt and other foreign matter from entering. Key operators may be used with identical locks, dissimilar locks, or with dissimilar locks having a master key system.

13. Module 1: Push Buttons Pushbutton Station Descriptions Pushbutton Schematic Symbols Pushbutton operators come in various types and configurations. Below the common types are illustrated: Stop Pushbutton Stop Pushbutton with multiple contacts Emergency Stop Emergency Stop with multiple contacts Start Pushbutton Start Pushbutton with multiple contacts

14. Module 1: Push Buttons Selector Switch Operators Selector Switches can be obtained in two, three, four, and etc. position types. Cams in the operator sleeve actuate the contact blocks. These selector switches can provide maintained or spring return contact operation. Many circuit combinations can be made since there is a number of different operating cams available and a variety of contact blocks. Selector Switch Schematic Symbols Selector switch operators come in various types and configurations. Below the common types are illustrated: Selector switch 2 position 2 contacts Selector switch 3 position 3 contacts

15. Module 1: Push Buttons Key Operated Selector Switch Key operated selector switches work just like normal selector switches plus a key locking feature to prevent unauthorized change or accidental tripping from a selected position. These switches also provide maintained or spring return momentary cam action on the contact plungers. Key Operated Selector Switch Schematic Symbols Key operated Selector switch 2 position 2 contacts

16. Module 1: Push Buttons Illuminated Pushbuttons These devices combine the functions of both a pushbutton operator and an indicating light in a single unit and require only half the space of two separate units. The light unit may be either a resistor type or an encapsulated transformer. These units are usually designed to give illumination from all angles. The contact blocks can still be used for circuit control as before. A rubber diaphragm in the operator, a rubber lens gasket, and a rubber panel gasket can provide oil tight assembly.

17. Module 1: Push Buttons Pushbutton Safety 1. Pushbuttons are pilot devices and must be ruggedly constructed to withstand operator and mechanical abuse. They are frequently exposed to oils, coolants, chemicals, dust and various foreign elements. This is why all pushbuttons, selector switches, indicating lights, and control stations shall be of the oil tight type. 2. All control stations shall be mounted in a reasonably clean and dry location. 3. Pushbuttons shall be mounted on a surface that is not less than 45 degrees from the horizontal plane. This is to help prevent dust or dirt from falling into them that could cause sticking. 4. All start pushbuttons shall be mounted above or to the left of their associated stop pushbuttons. 5. Stoppushbuttons shall be red in color, and the red color shall not be used to identify pushbuttons having other functions. They shall be the unguarded types, so they can be activated easily with the palm of a hand or other parts of the body.

18. Module 1: Push Buttons Pushbutton Safety 6. Start pushbuttons shall be of the fully guarded type, so they cannot be activated accidentally. There should be a definite intent to push the button before the machine can start. 7. Pushbuttons shall retain their color identification throughout their life. The buttons should also never be painted to change their function.

19. Module 1: Push Buttons End of Module 1 Push Buttons

20. Module 2: Limit Switches Module 2 Limit Switches

21. Module 2: Limit Switches Limit switches are devices used for interlocking a mechanical motion or position with an electrical circuit. The selection of a limit switch involves both electrical application requirements and mechanical placement. Limit switches are normally in the control circuit and can start a machine in motion or stop its motion. They can also restrict the travel of a machine between two points or possibly initiate a separate action at a pre-determined point of machine travel. Limit switches are also often used in safety devices for the protection of both personnel and equipment. Types of Limit Switches The function performed by limit switches is similar no matter how complex the design of the electrical circuit. The main differences are the mechanical design and the means by which the switch is actuated. Actuators An actuator is the external linkage that detects the mechanical movement of the machine. This actuates an internal mechanism that results in contacts opening or closing.

22. Module 2: Limit Switches Examples of Actuators

23. Module 2: Limit Switches Limit Switch Schematic Symbols Normally open limit switchNormally open held closed limit switch (N.O.) (N.O.H.C.) Normally closed limit switchNormally closed held open limit switch (N.C.) (N.C.H.O.)

24. Module 2: Limit Switches Common Detector Symbols Pressure Switch N.O. Pressure Switch N.C. Float Switch N.O. Float Switch N.C. Flow Switch N.O. Flow Switch N.C. Thermal Switch N.O. Thermal Switch N.C. Foot Switch N.O. Foot Switch N.C.

25. Module 2: Limit Switches End of Module 2 Limit Switches

26. Module 3: Inductive Proximity detectors Module 3 Inductive Proximity Detectors

27. Technical Mathematics Module 3: Inductive Proximity Detectors Inductive Proximity Detectors These devices can fulfill the same functions as the mechanical limit switch contacts, and have the following advantages: - Rapid speed of operation - Insensitive to humid or damp surroundings Principles of Operation Inductive proximity sensors are designed to operate by generating an electromagnetic field and detecting the eddy current losses generated when ferrous and nonferrous metal target objects enter the field. The sensor consists of a coil on a ferrite core, an oscillator, a trigger-signal level detector and an output circuit.

28. Module 3: Inductive Proximity Detectors As a metal object advances into the field, eddy currents are induced in the target. The result is a loss of energy and a smaller amplitude of oscillation. The detector circuit then recognizes a specific change in amplitude and generates a signal which will turn the solid-state output “ON” or “OFF.”

29. Module 3: Inductive Proximity Detectors The active face of an inductive proximity switch is the surface where a high-frequency electro-magnetic field emerges. A standard target is a mild steel square, one mm thick, with side lengths equal to the diameter of the active face or three times the nominal switching distance, whichever is greater.

30. Module 3: Inductive Proximity Detectors To determine the sensing distance for materials other than the standard mild steel, a correction factor is used. The composition of the target has a large effect on sensing distance of inductive proximity sensors. If a target constructed from one of the materials listed is used, multiply the nominal sensing distance by the correction factor listed in order to determine the nominal sensing distance for that target. Note that ferrous-selective sensors will not detect brass, aluminum or copper, while nonferrous selective sensors will not detect steel or ferrous-type stainless steels.

31. Module 3: Inductive Proximity Detectors The difference between the On and Off points is called hysteresis or differential travel. The amount of target travel required for release after operation must be accounted for when selecting target and sensor locations. Hysteresis is needed to help prevent chattering (turning on and off rapidly) when the sensor is subjected to shock and vibration or when the target is stationary at the nominal sensing distance.

32. Module 3: Inductive Proximity Detectors The switching frequency is the maximum speed at which a sensor will deliver discrete individual pulses as the target enters and leaves the sensing field. This value is always dependent on target size, distance from sensing face, speed of target and switch type. This indicates the maximum possible number of switching operations per second. Sensors can be connected in series with a load. For proper operation, the load voltage must be less than or equal to the minimum supply voltage minus the voltage drops across the series connected proximity sensors.

33. Module 3: Inductive Proximity Detectors Sensors can be connected in parallel to energize a load. To determine the maximum allowable number of sensors for an application, for an application, the sum of the maximum leakage current of the sensors connected in parallel must be less than the maximum OFF-state current of the load device.

34. Module 3: Inductive Proximity Detectors TTL Wiring

35. Module 3: Inductive Proximity Detectors Wiring Configurations Cable Style Proximity Switch

36. Module 3: Inductive Proximity Detectors Wiring Configurations Micro Style Proximity Switch

37. Module 3: Inductive Proximity Detectors Wiring Configurations Pico Style Proximity Switch

38. Module 3: Inductive Proximity Detectors Wiring Configurations AC Limit Style Proximity Switch

39. Module 3: Inductive Proximity Detectors Various Styles of Proximity Detectors Miniature Flat Pack Series Power and Gripper Applications

40. Module 3: Inductive Proximity Detectors Various Styles of Proximity Detectors Cylinder PositionSeries Ring and Slot Applications

41. Module 3: Inductive Proximity Detectors This concludes Module 3 Inductive Proximity Detectors

42. Module 4: Ultrasonic Proximity Detectors Module 4 Ultrasonic Proximity Detectors

43. Module 4: Ultrasonic Proximity Detectors Ultrasonic sensors operate by emitting and receiving high-frequency sound waves. The frequency is usually in the order of 200 kHz, which is too high for the human ear to hear. There are two basic modes of operation: opposed mode and diffuse (echo) mode. In opposed mode, one sensor emits the sound wave and another, mounted opposite the emitter, receives the sound wave. In diffuse mode, the same sensor emits the sound wave and then listens for the echo that bounces off an object.

44. Module 4: Ultrasonic Proximity Detectors The sensing range is the distance within which the ultrasonic sensor will detect a target under fluctuations of temperature and voltage. Ultrasonic sensors have an inherent blind zone located at the sensing face. The size of the blind zone depends on the frequency of the transducer. Objects located within the blind spot can not be reliably detected. Certain characteristic of targets must be considered when using ultrasonic sensors. These include target shape, material, temperature, size and positioning. Soft materials such as fabric or foam rubber are difficult to detect by diffuse ultrasonic technology because they are not sound-reflective.

45. Module 4: Ultrasonic Proximity Detectors Various Types of Ultrasonic Proximity Detectors by Allen Bradley

46. Module 4: Ultrasonic Proximity Detectors For normal operation do not connect the control pin. Hold and synchronize features can be used for special applications. To inhibit sensor operation and hold the output to its present state connect the control pin (2) to 0V DC. The sensor will not transmit or receive ultrasonic pulses until this voltage is removed from the control pin. Switching output models will be latched and analog output models will hold their value during this period. To synchronize the transmission of ultrasonic pulses between several sensors connect the control pins together. This feature reduces the potential for sensor crosstalk between models that are mounted in close proximity to one another.

47. Module 4: Ultrasonic Proximity Detectors Typical Beam Pattern Analog Output Styles

48. Module 4: Ultrasonic Proximity Detectors Discrete and Analog Output Styles

49. Module 4: Ultrasonic Proximity Detectors This Concludes Module 4 Ultrasonic Proximity Detectors

50. Module 5: Capacitive Proximity Detectors Module 5 Capacitive Proximity Detectors