Introduction to Switches and Limit Switches

Introduction to Switches

• Switches are essential components in automated systems, allowing for the control of electrical circuits and power flow.
• Switches come in various configurations and types, each with specific functionalities.
• Different types of switches are classified by their "poles" (connections to the switch) and "throws" (possible positions of the switch).
• A double pole, double throw (DPDT) switch can connect one side to either of two contacts on the other side.
• Rotary switches are used for multiple throws.
• In automation, safety is paramount, and momentary switches are often used with a single stable, off-state.
• These momentary switches are called "emergency power off" (EPO) and commonly come in push button configurations.

Limit Switches: Mechanical Actuation

• Unlike manual switches, limit switches are actuated automatically by the system or its components.
• These switches come in countless variations, designed specifically for their application, taking into account factors like size, lever travel, force, and ruggedness.
• Limit switches are designed to be robust enough for harsh industrial environments.
• They are used extensively in robotics and automation, limiting travel, acting as interlocks, etc.
• Some common actuators for limit switches include levers, toggles, push buttons, plungers, rollers, and cat whiskers.

Proximity Switches: Sensing Without Touch

• Proximity switches differ from traditional switches by sensing the presence of an object without physical contact.
• Two major types of proximity switches include ferrous metal detectors and ferrous/nonferrous metal detectors.
• Some proximity switches utilize electromagnetic antennas that detect disruptions in the signal field, while others utilize sonar systems that transmit and receive pressure waves to sense objects.

Photoelectric Systems: Leveraging Light for Sensing

• Photoelectric systems utilize light beams to detect object presence or absence, typically using photocells.
• Photoelectric systems are versatile and reliable but can be susceptible to environmental factors like ambient light, dust, and condensate.
• Common solutions to these challenges include shielding, mirrors, air jets, overdesigning, and using retroreflective systems.

Infrared Sensors: Beyond Visible Light

• Infrared sensors operate with invisible infrared radiation, offering advantages over photoelectric systems like immunity to stray light.
• They are useful for detecting heat sources and are often employed in monitoring systems.
• Modulated infrared beams are gaining popularity for enhanced intensity and precise sensing.
• Solid-state LEDs (light-emitting diodes) are favoured over incandescent bulbs for their low power consumption and high reliability.

Fiber Optics: Guiding Light Where Needed

• Fiber optic light tubes are flexible pipes that transmit light beams, effectively bending them around corners.
• They offer high efficiency and are used in various applications, including telecommunications and automation.
• Bundles of fibers enable the transmission of images.

Lasers: Precision and Power

• Lasers produce highly concentrated and amplified beams of light, useful for precise sensing and industrial applications.
• Their long, precise beams allow for accurate detection of small objects at various distances.
• Lasers are also employed for dimensional measurements.

Analyzers: Processing Information

• Once information is sensed by an automated system, it needs to be analyzed to determine appropriate actions.
• Digital computers are the primary means of analyzing automation system inputs, offering incredible versatility and programmability.

Counters: Keeping Count

• Automated systems often require counting the number of items or events, which can be performed by counters.
• These counters can be mechanical or electronic, with electronic counters becoming increasingly common in automated systems.

Solenoids: Electromagnetism for Linear Motion

• Solenoids utilize electromagnetism to produce linear motion.
• The core of a solenoid is pulled into the coil when energized by an electrical current.
• Solenoids are widely used in automation for quick, discrete actions, like switching electrical circuits.

Relays: Electromagnetic Switching

• Relays are solenoids that actuate switches in electrical circuits.
• They are often employed in logic networks to control power circuits.
• Relays can be either latching (holding a state until released) or non-latching (requiring continuous energization).
• Relays can be configured as normally-open (circuit made when energized) or normally-closed (circuit broken when energized).

This quiz covers the fundamentals of switches, including their types, configurations, and functionalities. It explains the role of limit switches, focusing on their automatic actuation in various applications. Enhance your understanding of these essential components in automated systems.