Pushing the Limits: A Comprehensive Guide to Push Button Switches

What is a push button switch?

A push button switch is an electrical switch that is activated by pressing a button or a small plunger. It is a type of momentary switch, which means that it only maintains contact while the button is being pressed, and as soon as the button is released, the switch returns to its normal position, breaking the circuit. Push button switches are commonly used in a variety of electronic devices and appliances, such as doorbells, calculators, and computers, where they are used to initiate a specific function or action. They are available in a range of sizes, shapes, and configurations, including momentary or latching types, illuminated or non-illuminated, and with different contact arrangements.

Fig 1. Push Button Switches 101

How does the push button switch work?

Push button switches work by creating a connection between two electrical contacts when the button is pressed, and breaking that connection when the button is released. The switch has a plunger or button that, when pressed, moves a set of contacts together, completing an electrical circuit. When the button is released, a spring or other mechanism returns the contacts to their original position, breaking the circuit.

In a momentary push button switch, the electrical connection is only maintained as long as the button is pressed. This type of switch is commonly used as a momentary contact switch to trigger a specific action, such as turning on a light or activating a motor.

In a latching push button switch, the contacts remain connected even after the button is released until the switch is pressed again to break the connection. This type of switch is commonly used as an on/off switch, such as in a power tool or a light switch.

Push button switches can also come in a variety of configurations and with additional features, such as illumination, tactile feedback, or anti-vandal protection, depending on the application and requirements.

Fig 2. Push button operation

What are the types of push button switches?

Push button switches are either usually normally open (NO) or normally closed (NC). When activated, normally open ("OFF") switches complete the circuit, whereas normally closed ("ON") switches break the circuit. Push button switches' functionality can be further defined within this group by the switching circuit they use. Single pole, single throw (SPST), single pole, double throw(SPDT), double pole, single throw (DPST), or double pole, double throw (DPDT) are the most popular of these switching circuits.

Normally Open

An electrical switch is generally an open switch. A normally open switch remains off if it is not compressed. This is due to the electrical connections on the inside. When a normally open switch is turned off, the contacts are open. This indicates that the electrical connection has been severed, and the switch is off. The contacts of normally closed switches are closed, which connects to the switch, and when they are not compressed, they are switched on. Momentary normally open switches and latching normally open switches are both available options.

Fig 3. Normally open

A momentary switch must be continuously compressed, whereas a latching switch just needs to be pressed once to change state. The vast majority of switches are generally turned on. Here are a few examples:

Light Switch– Light switches are normally open-latching switches. They are open until squeezed, at which point they close until pressed again and switched off.

Medical Bed Controls – Medical bed controls can be footswitches or hand controllers, and are often open momentary switches. When they are not compressed, the switch remains open, requiring the user to continuously press the switch for the bed to move to the desired height; once the compression is removed, the switch closes and the bed stops moving.

Medical and Industrial Equipment – Much equipment in medical and industrial settings use normally open switches, notably footswitches which provide operators with the ability to still use their hands. When the footswitch is pressed, the circuit is closed, allowing the machinery to operate. Examples of this application type are as follows:

• Sewing machines
• Medical machinery
• Metal cutting machines
• Metal bending machines
• Tattoo machines
• Optical instruments
• Hair removal devices

Normally Closed

A normally closed contact remains closed in the absence of any force, energy, or involvement with the switch. The normally closed contact can only be opened by applying some type of energy, either mechanical or electrical. As a result of the delivered energy, the force that actuates the switch is created, and the normally closed contact changes its state to an open one.

Fig 4. Normally closed

The switch's contact is known as normally closed contact when it is closed without the application of any force, energy, or participation with the switch. A normally closed switch's primary application would be an emergency stop. When the switch is not pressed, the circuit remains closed. When pressed, it opens, causing the circuit to short and the power to be cut.

Single Pole, Single Throw

The single pole, single throw switch has one input and one output. A single input is directly coupled to a single output in this case. This switch's primary function is to control the circuit by turning ON/OFF. When the switch in the circuit is closed, the circuit is switched ON; if the switch is not closed or open, the circuit is turned OFF.

Fig 5. Single Pole, Single Throw

This switch has two types of connections: normally open (NO) and common (C). The circuit is closed when the switch gets on. The current will pass from the common (C) terminal to the ordinarily open (NO) terminal. When the switch is turned off, the circuit becomes an open circuit, with no current flowing through it. This switch acts as a one-way switch to turn the circuit on and off. When a user presses the switch button, the switch plates are connected. As a result, current begins to flow throughout the circuit. This switch, for example, is commonly used to control the light in the room. When the switch is turned OFF, the circuit is broken, and the light is turned off. Similarly, when the switch is switched on, the light is turned on.

The following are some of the benefits of the SPST switch:

• Simple circuit design
• Simple wiring
• Reduced cabling
• Lower costs
• Increased ability to function with high voltages & currents
• Reliability

The drawbacks of the SPST switch include:

• Possible confusion in its usage
• Lack of durability

Single Pole, Double Throw Switch

The single pole, double throw switch allows two distinct circuits to be controlled by a single common input. This switch can be operated manually or automatically through an electromagnetic coil. The output terminal relays of an ACS 550 or 800 VFD are the best example of a single pole, double throw switch. In this case, the relay switch can be configured as one input with two distinct outputs.

Fig 6.Single Pole, Double Throw Switch

The SPDT switch is just an ON/OFF switch that connects or disconnects two terminals. When the switch is closed, two terminals are connected, allowing current to flow between them. Similarly, when the switch is opened, the two terminals are not connected, and so no current is supplied. Based on how they operate, single pole double throw switches are classified into two types: BBM-type switches (Break Before Make) and MBB-type switches (Make Before Break).

Break Before Make (BBM) Type Switch

Transfer switches are designed to rapidly transition electrical power. An open transition is referred to as a break before making (BBM) the transfer, where the transfer switch breaks its connection to one power source before it connects to another power source. During the disconnection and connection, no power is provided to the downstream load.

A BBM SPDT switch is connected to the closed throw circuit and disconnected from the open throw circuit by default. When the BBM switch is actuated, it disconnects from the closed circuit and then connects to the open circuit.

When the signal path is altered by the input control logic in devices with the BBM function, the link between two multiplexed pathways is never electrically connected. In most multiplexed applications, it is ideal to provide isolation between the two multiplexed pathways to avoid signal distortion while moving a signal from one channel to another.

Make Before Break (MBB) Type Switch

Another form of transition is a make-before-break switch, where the switch bridges between two positions. In this configuration, the second connection is made before the first connection is broken. The blade of the switch is coupled to a selector switch control where the blade is placed in a connection to the first power source position and a second position to load the electrical contact. T-shaped and V-shaped blades are used for this type of switch.

The pole of the MBB SPDT switch is connected to the NC throw circuit by default and disconnected from the normally open throw circuit. When the MBB switch is triggered, it first connects to the normally open circuit and then detaches from the normally closed circuit.

The MBB feature makes sure that when the signal path being picked is altered by the input control logic, the link between two multiplexed paths is never electrically severed. In cases where a feedback node needs a load to always be present, this will stop any cases of a high impedance output from ever being present.

Double Pole, Single Throw

The DPST switch is a switch with two inputs and two outputs, where each input has one corresponding output. Every terminal in this switch can be set to either ON or OFF. In this type of switch, “pole” refers to the number of circuits controlled by the switch, and “throw” refers to the actuator's extreme position. Double pole switches essentially regulate two independent circuits through a single throw switch that controls both circuits simultaneously.

Fig 7. Double Pole, Single Throw

The working idea of a DPST (double pole, single throw) switch is to control two distinct circuits at the same time; either both circuits are OFF or ON using a single actuator such as a push button, toggle, or similar device. These switches have four terminals, two inputs, and two outputs. However, multiple voltages from separate sources can be coupled to a single DPST switch. This switch receives two inputs and can drive two separate outputs in a circuit. These are fundamentally two SPST switches joined together that affect distinct circuits but are actuated by the same actuator.

The DPST switch has the following pros:

• Two unrelated circuits can be opened or closed at the same time.
• There is the usage of two independent circuits.
• There is a simultaneous function of the input-output pair.

The drawbacks of the DPST switch include:

• The switching work of both circuits must simultaneously be ON or OFF.
• The DPST switch is a more sophisticated, but more expensive ON/OFF switch as it connects or disconnects two circuits at the same time.

Double Pole, Double Throw

A DPDT (double-pole, double-throw) switch is an electromechanical switch constructed by adding a pole to an SPDT switch. This is very simple to install because it comes with a locking system that allows you to lock and unlock the switch directly in a remote cabinet without the use of any nuts, bolts, or screws. A DPDT switch has two inputs and four outputs, with each input having two equivalent outputs. Because each terminal in this switch can be in one of two places, it is extremely adaptable. This switch's inputs can be connected to four separate outputs, allowing it to switch a circuit between two modes of operation. This switch is a hybrid of two SPDT switches.

Fig 8. Double Pole, Double Throw

DPDT switches will break or split the two conductors attached to two independent circuits. DP switches regulate two distinct circuits in this switch, whereas DT switches close a circuit in the up and down positions. These switches have six terminals, two inputs, and four outputs, and are available in momentary or maintained contact configurations. The SPDT features are used to create this dual ON-ON switch. In general, this switch has two (ON-ON) or three (ON-OFF-ON) settings. The DPDT switch essentially allows two SPDT switches to communicate with one another via four circuits with two distinct circuit systems. These circuits can all be turned on at the same time.

As a result, once the switch is turned on, two appliances on identical circuits will be powered. Meanwhile, only two of the four circuits within a DPDT switch can be active at the same time. This switch uses polarity reversal to alternate between two powered circuits at the same time.

The DPDT switch has the following pros:

• The DPDT switch conveys two unrelated signals.
• It can function with high voltages & currents.
• They provide failover capabilities for computers.
• It can work on drive motors, pumps, and control relays because of its high current capabilities.
• The DPDT switch can be used in numerous areas.
• They provide a user the ability to control multiple appliances with the push or flick of a single button.
• The DPDT is economical when compared to installing multiple switches where each one only controls a single operation.
• This switch weighs less in comparison to multiple switches.

The drawbacks of the DPDT switch include:

• The switch is expensive compared to bridges.
• It is hard to trace network connectivity issues with the DPDT switch.
• Broadcast traffic is difficult.

What is the usage of the push button switch?

Push button switches are used in a variety of applications where a simple on/off or momentary contact switch is required. Some common uses of push button switches include:

1. Industrial controls: Push button switches are used in industrial machinery and equipment to control the start, stop, and operation of various functions.
2. Electrical circuits: Push button switches are used in electrical circuits to turn on/off lighting, fans, and other appliances.
3. Automotive industry: Push button switches are used in vehicles for starting the engine, operating lights, and other accessories.
4. Appliances: Push button switches are used in appliances such as coffee makers, blenders, and toasters to control the operation of the appliance.
5. Gaming: Push button switches are used in gaming controllers for controlling gameplay.
6. Medical equipment: Push button switches are used in medical equipment such as ECG machines, ultrasound machines, and monitors for controlling various functions.
7. Security systems: Push button switches are used in security systems to arm/disarm alarms or control access to restricted areas.

These are just a few examples of the many applications of push button switches. Their simplicity, reliability, and ease of use make them a popular choice in a wide range of industries and products.

Fig 9. Examples of different push button actuator heights

Pros and cons of the push-button switch

Push button switches have several advantages and disadvantages that are important to consider when selecting a switch for a particular application. Here are some of the pros and cons of push button switches:

Pros

1. Simplicity: Push button switches are simple to use and operate, making them user-friendly and easy to incorporate into designs.
2. Durability: Many push-button switches are designed to be robust and can withstand repeated use and abuse, making them ideal for industrial and outdoor applications.
3. Versatility: Push button switches are available in a wide range of styles, sizes, and configurations, making them suitable for a variety of applications.
4. Tactile feedback: Some push button switches provide tactile feedback, giving users confirmation that the switch has been activated.
5. Low power consumption: Push button switches generally require very little power to operate, making them suitable for battery-powered devices.

Cons

1. Limited functionality: Push button switches typically only provide a simple on/off or momentary contact function, which may not be suitable for more complex applications.
2. Limited control: Push button switches do not provide variable control, which may be required in some applications.
3. Wear and tear: The contacts in a push button switch can wear out over time, which can lead to the failure of the switch.
4. Sensitivity to environmental factors: Some push button switches may be sensitive to environmental factors such as moisture or dust, which can affect their performance.
5. Cost: High-quality push button switches can be expensive, which may not be suitable for cost-sensitive applications.

These are some of the advantages and disadvantages of push button switches that are important to consider when selecting a switch for a particular application.

Conclusion

Push button switches are simple and reliable devices that are used in a wide range of applications, from industrial machinery to household appliances. They work by creating a connection between two electrical contacts when the button is pressed, and breaking that connection when the button is released. There are different types of push-button switches available, including momentary and latching switches, which can be used for different purposes.

Push button switches have several advantages, including simplicity, durability, versatility, tactile feedback, and low power consumption. However, they also have some disadvantages, such as limited functionality, wear and tear, sensitivity to environmental factors, and cost.

Overall, push-button switches are a popular choice for many applications due to their ease of use, reliability, and versatility. When selecting a push button switch, it is important to consider the specific requirements of the application to ensure that the switch chosen is suitable for the task.

To recap

Here are some frequently asked questions (FAQs) about push button switches:

1.What is a push button switch?

A push button switch is a type of electrical switch that is activated by pressing a button or plunger. It is used to make or break an electrical circuit, typically to control a device or equipment.

2.What are the types of push button switches?

There are two main types of push button switches: momentary switches and latching switches. Momentary switches only remain closed as long as the button is pressed while latching switches remain closed even after the button is released until the switch is pressed again.

3.What are push button switches used for?

Push button switches are used for a variety of applications, such as controlling lights, fans, motors, and other electrical devices. They are commonly found in industrial machinery, household appliances, gaming controllers, medical equipment, and security systems.

4.What are the advantages of push button switches?

The advantages of push-button switches include their simplicity, durability, versatility, tactile feedback, and low power consumption.

5.What are the disadvantages of push button switches?

The disadvantages of push button switches include their limited functionality, wear and tear, sensitivity to environmental factors, and cost.

6.How do you wire a push button switch?

Wiring a push button switch involves connecting the switch to a power source and the device or equipment that it is controlling. The specific wiring diagram depends on the type of switch and the application and should be followed carefully to ensure proper operation.

7.Can push button switches be illuminated?

Yes, many push-button switches are available with built-in illumination, which can be useful for indicating the status of the switch or providing visual feedback in low-light conditions.

8.Are push-button switches waterproof?

Some push-button switches are designed to be waterproof or water-resistant, making them suitable for use in outdoor or wet environments. However, not all push-button switches are waterproof, so it is important to check the specifications before selecting a switch for a particular application.