Control Devices 211
Control Devices 211 covers the fundamental components of motor controls, devices that control the flow of current in circuits. Dangers of electric shock and other safety risks are significantly heightened when working with control devices. Control devices can be manual, mechanical, or automatic and are used in a variety of ways. Control devices include different types of buttons and switches, all of which serve differing purposes. It is necessary for those working with motor controls to understand control devices and apply their knowledge to appropriately select and operate these items according to application. After taking this course, students will be able to describe the design and function of commonly used mechanical control devices, along with applications appropriate for each device.
Number of Lessons 22
- Control Devices
- Types of Control Devices
- Types of Operators
- Control Devices and Pushbuttons Review
- Selector Switches
- Limit Switches
- Limit Switches in Operation
- Limit Switch Actuators
- Pressure Switches
- Selector, Limit, and Pressure Switches Review
- Pressure Sensing Devices
- Temperature Switches
- Temperature Sensing Devices
- Flow Switches
- Pressure, Temperature, and Flow Sensing Devices and Switches Review
- Level Switches
- Proximity Switches
- Photoelectric Sensors
- Troubleshooting Control Devices
- Level, Proximity, and Photoelectric Switches and Troubleshooting Review
- Define control devices.
- Describe the different types of inputs.
- Describe the different types of control devices.
- Describe the different parts of pushbuttons.
- Describe common pushbutton operators.
- Describe selector switches.
- Describe limit switches.
- Describe limit switches.
- Describe limit switch actuators.
- Describe pressure switches.
- Describe pressure sensing devices.
- Describe temperature switches.
- Describe the different types of temperature sensing devices.
- Describe flow switches.
- Describe level switches.
- Describe proximity switches.
- Describe photoelectric sensors.
- Describe control device troubleshooting practices.
To make a device or machine operate. Selector switches actuate contacts.
Makes a device operate or run. Pushbutton operators actuate electrical contacts.
The part of a limit switch that comes into contact with an object and triggers the switch. Limit switch actuators come in different styles: rotary levers, forks, plungers, flexible loops, and spring rods.
A component that pressurizes ambient air. Air compressors direct pressurized air into pneumatic systems.
A control device that runs independently of an operator. Automatic control devices receive signals from other devices that tell them when to start a process.
A control device that is set to determine and manage each step in a process independently. Automatic inputs include pressure switches, flow switches, and temperature switches.
A cylindrical device with several deep folds that expand or contract in response to pressure. Bellows are usually used at medium pressure.
Also known as a bimetallic strip, a sensor made of two unlike bonded metals that expand at different rates when heated. Bimetallic sensors provide a physical signal that the sensor converts into an electrical signal.
Also known as a bimetallic sensor, a sensor made of two unlike bonded metals that expand at different rates when heated. Bimetallic strips provide a physical signal that the sensor converts into an electrical signal.
capacitive proximity switches
A control device that is triggered when it detects either conductive or nonconductive substances. Capacitive proximity switches are able to detect both solid and liquid materials.
capillary tube sensor
A sensor that changes internal pressure when temperature changes. Capillary tube sensors use temperature sensitive liquid.
The occasional unwanted vibration between components. Chatter decreases machining productivity, negatively impacts surface quality, and increases tool wear.
The different options that selector switches allow technicians to choose. Circuit conditions may include options such as "left/right," "up/down," "manual/automatic," and "on/off."
Computer numerical control machine. A machine controlled by a computer that performs a series of operations. CNC machines contain control devices such as switches to help them function safely.
Wire that is wrapped around a magnetic core. Coils conduct electrical current in a circuit.
The end of a thermocouple that provides a reference point. The cold junction is held at a constant temperature.
A conductive metal part that opens or closes a circuit by separating from or touching a matching part. Contacts are components of electrical circuits.
Pushbutton components that hold contacts and are activated when pushbuttons are pressed. The most common contact block has one normally open (NO) and one normally closed (NC) contact.
A device that uses a small control current to energize or de-energize a load. Contactors can handle high amounts of current and are also combined with overload relays to create motor starters.
Any input device that controls the flow of current in a circuit. Control devices determine when loads are energized or de-energized.
An electrical switch that opens and closes a circuit. Relays can open or close one or many sets of contacts.
A passage through which cooling fluid is circulated. Cooling lines assist in maintaining the desired temperature in a system.
The flow of electricity through a circuit. Current in a circuit can be controlled by control devices.
The amount of pressure that must change before pressure switch contacts reset after actuation. Deadband pressure is also referred to as differential pressure.
A spring-loaded valve mechanism that moves in response to variations in pressure in a pneumatic system. The diaphragm is a flexible membrane that responds to pressure changes.
DMM. A device that can measure voltage, current, or resistance. A digital multimeter is the most versatile and common meter used today for electrical maintenance.
A magnetic current created by sensor vibration. Eddy currents flow out and around the head of a sensor.
A controlled path that contains electrical current. Electrical circuits are controlled by control devices.
electrical control devices
A type of control device that senses the presence of an object without touching it. Electrical control devices include proximity switches and photoelectric switches.
E-stop. A switch or button that brings a machine to a safe, rapid stop. Emergency stops are often mushroom button operators.
extended button operator
A pushbutton operator whose button extends beyond its guard. Extended button operators are used in situations where accidental startup is not dangerous.
A device used in switches that floats on liquid. Floats rise or fall based on the level of the liquid.
A mechanical device that is used to move liquids or gases. Fluid pumps are used in hydraulic and pneumatic systems.
flush button operator
A pushbutton operator that has a guard ring that sits at the same level as the operator. Flush button operators are used in situations where accidental startup is dangerous.
The piece of circular material surrounding a flush button operator. Guard rings prevent unintentional starting of an operation or machine.
The end of a thermocouple that measures temperature. The hot junction is exposed to the elements.
A system that uses liquids to transmit power. Hydraulic systems rely on fluid force to run different systems.
A device that lights up to signal something. Indicator lights may flash when normally open (NO) contacts close.
inductive proximity switches
A control device that is triggered when it detects a conductive substance. Inductive proximity switches operate using eddy currents.
A device that enters in and contributes to a process. Inputs are a type of control device.
A common circuit condition that lets a technician run a machine intermittently, power it down, or run it consistently. "Jog/off/run" is a common circuit condition on a three-position selector switch.
Circuit conditions that allow a technician to make a machine function intermittently or consistently. The "jog/run" choice of conditions is the most common set of conditions on a two-position selector switch.
The part of a switch that displays the function of the switch's operation. Legend plates surround pushbuttons.
A device that detects the height of a liquid or solid in a tank or another type of vessel. The most common type of level switch is the mechanical level switch.
A device that emits beam of light received by a photosensor. Light sources are used to trigger photoelectric sensors.
limit switch actuator
The part of a limit switch that contacts an object and triggers the switch to perform an action. Limit switch actuators come in two different categories: rotary and plunger.
A switch that detects the presence an object by physically touching it. Limit switches have a variety of actuators that come into contact with an object.
A device that converts electricity into light, heat, or mechanical motion. Loads are components of electrical circuits.
lower set level
The minimum level at which a technician has set a pressure switch to operate. Once pressure has reached the lower set level, contacts will close or open and remain in that condition until pressure rises.
A control device that requires an operator to activate or deactivate it. Manual control devices include pushbuttons.
A control device that requires individuals to press a button or turn a switch. Manual inputs include pushbuttons and selector switches.
A device that must make physical contact with an object to operate. Mechanical control devices include limit switches.
mechanical control devices
A device that physically contacts objects. Mechanical control devices include limit switches, flow switches, and level switches.
A control device that must touch an object in order to detect it. Mechanical inputs include limit switches.
mechanical level switch
A device that uses a float to trigger electrical contacts. Mechanical level switches are used to detect liquid levels when they reach a set height.
An electrically operated switch that uses magnetic induction to provide the startup current for a motor.
mushroom button operator
A pushbutton operator that extends beyond its guard. Mushroom button operators have large, rounded heads and can be easily accessed.
Normally closed contacts. Electrical devices that allow electricity to flow. When an NC contacts open, electricity stops flowing.
Normally open contacts. Electrical devices that prevent electricity from flowing. When NO contacts close, electricity starts flowing.
NC. An electrical contact that allows electricity to flow. If an NC contact opens, electricity stops flowing.
NO. An electrical contact that does not allow electricity to flow. If an NO contact closes, a circuit may be formed.
The part of a switch that is pressed, pulled, or turned by an individual operating the circuit. Operators come in a variety of styles and sizes.
An activity or result of a process. Outputs triggered by contacts closing can range from the flashing of an indicator light to the sounding of a warning bell.
A hinged actuator used in many types of flow switches. The flow of fluid deflects the paddle, actuating the flow switch contacts.
A control device, also known as a photoelectric switch, that detects the presence of an object through the use of a beam of light. When the beam of light is interrupted, the sensor sends a signal through the circuit that affects the operation of the machine in a specific way.
A control device that detects light. Photosensors detect the presence of an object using a beam of light.
A piece of metal that moves up and down inside a hollow cylinder in response to a pressure change in pneumatic and hydraulic systems. Pistons may be used to transfer motion to brake components.
A limit switch actuator in the form of a button that is depressed to activate the switch. Plunger actuators come in three basic styles.
A system that uses gases to transmit power. Pneumatic systems rely on gas to run a system.
A device that generates electricity. Power sources are components of electrical circuits.
pressure sensing devices
A control device that is designed to detect a range of pressures in motor control systems. Pressure sensing devices include diaphragms, bellows, and pistons.
A control device, also called a proximity switch, that uses an electronic sensing field to sense the presence of an object without touching it. Proximity sensors can detect the presence of almost any liquid or solid.
A manual control device that opens or closes a circuit when pressed. Pushbuttons can be normally open or normally closed.
Manual control devices that open or close a circuit when pressed. Pushbuttons can be normally open or normally closed.
A mechanism designed to receive light. When receivers do not receive light from the photosensor, an object or person is in its path.
An electrically controlled mechanical device that controls one circuit by opening or closing contacts in another circuit. Relays can open or close one or many sets of contacts.
The opposition to current flow. Electricity flows in the path of least resistance.
A device that restricts current flow. Resistors produce work, such as heat or light.
A limit switch actuator with a handle that directs force in a circular motion. Rotary actuators come in a range of styles and sizes to be used in a variety of applications.
A device that can be turned to different positions to make a connection with contacts in that particular position. Selector switches allow technicians to operate machines under different conditions.
A switch that can be turned to different positions to make connections with the contacts in that particular position. Selector switches can allow technicians to operate machines under different conditions.
A circuit where current takes a shorter, unintended path between two conductors. Shorts, also known as short circuits, cause excess current flow.
A metal guard plate connected to a limit switch that prevents damage to the switch. Stop plates keep limit switches from being forced beyond their travel limit.
A machine that uses a rotating wheel to wear away precise amounts of a flat workpiece surface. Surface grinders rely on limit switches to keep them from being damaged.
A control device that can make or break a circuit by closing or opening. Switches can be manual, mechanical, or automatic.
A switch that reacts to different heat intensities and activates electrical contacts when the temperature rises above or drops below a set level. Temperature switches are often used in heating and cooling systems.
A resistor that is temperature sensitive. As the temperature changes, the resistance of a thermistor changes.
A temperature sensor that measures heat at a hot junction and outputs voltage at a cold junction. Thermocouples output voltage that is proportional to the measured temperature.
A selector switch that allows you to select one of three circuit conditions. The third position is usually "off," as in "forward/reverse/off."
A selector switch that allows a technician to select one of two circuit conditions. Common two-position selector switches are "on/off" and "forward/reverse."
upper set level
The maximum level at which a technician has set a pressure switch to operate. Once pressure has reached the upper set level, contacts will close or open and remain in that condition until pressure falls.
A part that is worked on during manufacturing processes. Workpieces may be subjected to cutting, welding, forming, or other operations.
A switch that detects the movement of any fluid, such as liquid, gas, or air, in a system. Flow switches are commonly used in fluid pumps and air compressors.
A switch that detects the movement of any fluid, such as liquid, gas, or air, in a system. Flow switches are commonly used in fluid pumps and compressors.
A control device, also known as a photoelectric sensor, that detects the presence of an object through the use of a beam of light. When the beam of light is interrupted, the switch sends a signal through the circuit that affects the operation of the machine in a specific way.
A switch that uses a light beam to detect the presence of an object without touching it. Photoelectric switches can detect lightweight objects, heavy objects, or objects that are too hot.
A device that detects a certain amount of force and activates electrical contacts when the force is reached. Pressure switches have different sensing devices that detect pressure changes.
A switch that detects a certain amount of force and activates electrical contacts when the force is reached. Pressure switches have different sensing devices that detect pressure changes.
A control device, also called a proximity sensor, that uses an electronic sensing field to sense the presence of an object without touching it. Proximity switches can detect the presence of almost any liquid or solid.
A switch that uses an electronic sensing field to sense the presence of an object without touching it. Proximity switches can detect the presence of almost any liquid or solid.