Push Button Switches: A Complete Overview

A push button switch is a fundamental electrical component used to control various actions in machines and processes. These switches are ubiquitous in our daily lives, found in homes, workplaces, and outdoor environments. Commonly referred to as pushbutton switches or simply push switches, they serve as simple yet effective interfaces for user interaction.

Typically constructed from durable materials like plastic or metal, push button switches can feature either flat surfaces or ergonomic designs tailored for comfortable use. They operate through basic electrical mechanisms or air switch mechanisms, allowing users to easily turn devices on or off. There is a diverse range of push button switch models available, powered by two primary action types: momentary and latching.

• Momentary switches require continuous pressure to maintain the circuit connection, while releasing the button interrupts the flow.
• Latching switches, on the other hand, maintain their state until pressed again, providing a stable on/off function.

Push button switches are integral components in many applications, from controlling home appliances to operating complex industrial machinery.

The operation of most push button switches is straightforward yet effective. When pressure is applied to the actuator (the button), it compresses an internal spring and engages electrical contacts within the switch. This action either closes or opens an electrical circuit, allowing current to flow or stopping it entirely. Repeated pressure will retract the spring, toggling the state of the switch.

Users can choose between push buttons that feature normally open (NO) or normally closed (NC) contacts:

• Normally Open (NO): The circuit is activated only when the button is pressed.
• Normally Closed (NC): The circuit remains active until the button is pressed.

This versatility makes push button switches suitable for various applications, from everyday devices like elevators and remote controls to critical safety functions in industrial environments.

The simplicity and effectiveness of push button switches make them integral to controlling electrical circuits in numerous applications, ranging from household appliances to complex industrial machinery. These switches are commonly found in devices such as calculators, push-button telephones, and a variety of domestic and workplace appliances. They serve multiple functions, including turning devices on or off and initiating specific actions, such as inputting numbers in a calculator.

To enhance usability and prevent accidental activation, many push button switches feature distinct colour coding. For instance, red buttons often signify a stop function, while green buttons typically indicate a start action. Emergency stop buttons are usually large and red for easy identification and quick access in critical situations.

Push button switches are versatile and can be found in numerous applications, including:

• Reset Switches: Often small in size, these switches can be activated using a specialised tool to reset devices or systems.
• Machinery Control: In industrial settings, distinctive push button switches are strategically placed on or near machinery to allow for immediate shutdown in emergencies.
• Household Appliances: Commonly integrated into devices like washing machines, microwaves, and dishwashers, push button switches allow users to easily manage different functions.
• Automotive Applications: Modern vehicles utilise push button switches for various functions such as engine ignition, light control, and window operation.
• Medical Equipment: In healthcare settings, these switches are vital for operating devices like infusion pumps and diagnostic equipment, ensuring precise control during critical procedures.
• Security Systems: Push button switches play a crucial role in arming or disarming alarms, controlling access points, and triggering emergency alerts.
• Lifts and Escalators: Push button switches are essential for selecting floors and operating these transportation systems efficiently.

Arduino Push Buttons

Arduino push buttons are specifically designed for integration with Arduino circuit boards, allowing users to control various devices easily. Supported by a global community of makers and developers, these buttons enable seamless interaction with a wide range of electronic projects and prototypes.

2-Position Push Button Switches

These switches have two distinct positions, on and off, allowing users to control connected devices effectively. Often encased in protective plastic, they may require a key for operation, making them suitable for applications where security is essential.

Dual Push Button Switches

Similar to 2-position switches, dual push button switches feature one button for activation (typically green) and another for deactivation (usually red). They often include LED indicators to visually signal the device's status, enhancing user experience.

Miniature Push Button Switches

Miniature or micro push button switches are compact devices commonly used in small electronic devices for functions like resetting or initiating processes. Brands like C&K offer a variety of these switches designed for tight spaces.

Push to Break Switches (Normally Closed)

Also known as normally closed (NC) switches, push to break switches allow electricity to flow until the button is pressed. This type of switch is commonly used in emergency stop applications where immediate interruption of power is necessary.

Push to Make Switches (Normally Open)

In contrast, push to make switches enable current flow only when the button is pressed. Releasing the button breaks the circuit. These switches are often found in doorbells and calculators and can sometimes feature both push-to-make and push-to-break functionality.

Circuit Board Push Button Switches

These switches are integrated directly onto printed circuit boards (PCBs), controlling electricity flow through user interaction. They are commonly used in keyboards, keypads, and control panels.

Tactile Push Button Switches

Also known as tact switches, tactile push buttons require minimal force to operate and provide tactile feedback through a clicking sound when activated. Some models feature LED illumination to indicate operational status or faults.

Panel Mounted Push Button Switches

Designed for sturdy mountings, panel-mounted push buttons require specific cut-out sizes as indicated in the technical datasheets. They are widely used in both domestic and industrial settings for powering electronic devices.

Locking Push Button Switches

Locking push button switches incorporate a mechanical locking mechanism that prevents accidental activation after release. Users must press the button again to unlock it, which was a common feature in older television sets.

Industrial Push Buttons

These robust units include an actuator, fixing collar, and contact block designed for easy installation in industrial environments where manual intervention is required for controlling heavy machinery safely.

Push to Make Door Switches

Surface-mounted push-to-make door switches facilitate electrical operations for sliding or standard doors. Typically made from durable plastic, they can accommodate various door types effectively.

When selecting a push button switch, it is crucial not to assume that a switch will be suitable simply because its current rating does not exceed the maximum circuit load. One of the most important specifications to consider is the voltage rating, which can vary significantly between alternating current (AC) and direct current (DC) applications. Understanding these differences is essential for ensuring safe and effective operation in your specific application.

Push button switches are rated for different voltages, typically ranging from 24V to 250V for both AC and DC applications. For instance, if a switch has a maximum rated voltage of 24V DC, it can safely be used in circuits operating within that voltage range. However, exceeding this rating can lead to switch failure or safety hazards.

The distinction between AC and DC ratings is critical. AC circuits experience a natural zero crossing twice per cycle, which helps extinguish any voltage arcs created when the switch opens. Conversely, in DC circuits, the current flows steadily in one direction, making it more challenging to interrupt the circuit without generating a sustained arc. This prolonged arcing can lead to contact pitting, overheating, and ultimately premature switch failure.

Another vital factor to consider is the nature of the electrical load being switched. The suitability of a push button switch depends on whether it will be controlling an inductive load (such as motors or transformers) or a resistive load (like heaters or incandescent bulbs).

• Inductive Loads: When switching inductive loads, there is often a significant inrush current at startup that can be several times greater than the steady-state current. This surge can cause high voltage spikes when the circuit is opened, leading to potential damage if the switch is not rated appropriately.
• Resistive Loads: In contrast, resistive loads typically reach their steady-state current immediately upon activation without significant inrush currents, making them easier on switches.

When selecting a push button switch, it's essential to consider several factors to ensure that you choose the most suitable type for your specific application. Here are key considerations to guide your decision:

1. Application Requirements

• Functionality: Determine the primary function of the switch. Will it be used for momentary actions (e.g., starting a machine) or latching actions (e.g., toggling a light)? Understanding the operational requirements will help you choose between momentary and latching push button switches.
• Load Type: Identify whether the switch will control resistive loads (like heaters) or inductive loads (such as motors). This distinction is crucial because inductive loads can cause arcing and require switches rated for higher inrush currents.

2. Actuator Style

• Shape and Size: Push button switches come in various shapes and sizes, including round, square, and rectangular buttons. Consider the space available for installation and the ergonomics of use.
• Illumination: Some switches feature built-in LEDs to indicate status (on/off). This can enhance user experience, especially in low-light conditions.

3. Environmental Considerations

• Ingress Protection (IP) Rating: If the switch will be used in harsh environments (e.g., outdoors, industrial settings), look for switches with high IP ratings to ensure they are dustproof and waterproof.
• Temperature Range: Consider the operating temperature range of the switch. Some applications may expose switches to extreme temperatures, requiring specialised components.

4. Mounting Options

• Panel Mount vs. PCB Mount: Decide whether you need a panel-mounted switch or one designed for direct mounting on a printed circuit board (PCB). Panel-mounted switches are typically easier to access, while PCB-mounted options are more compact.

5. Safety Features

• Emergency Stop Functionality: For industrial applications, consider switches with emergency stop capabilities. These switches are designed to be easily accessible and typically feature larger buttons for quick activation in emergencies.