What is a Push Button or Push Switch?
A push button is an electromechanical component used in electronics, electricity, and/or control systems to send electrical signals or commands, either momentarily or indefinitely, to an electrical circuit by pressing a button with a finger. Generally, circuit activation or deactivation occurs only momentarily, during the action of pressing the button.
How Many Types of Push Buttons Are There?
There are two main types of push buttons, based on the action:
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Momentary Push Button or Non-Latching: The basic operation of a momentary push button involves closing or opening an electrical contact when the button is pressed, allowing the current to flow or cease flowing through the circuit. When the button is released, the contact opens again, interrupting the current. In other words, the state change (open to closed or vice versa) is momentary and depends on the pressure exerted on the button.
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Maintained Push Button with Latching: This type of push button is also manually actuated by pressing, causing the electrical signal to flow through the circuit or stop flowing. However, unlike the momentary push button, the state of the maintained push button is independent of the disappearance of the pressing action that caused the change. It would be necessary to press the button again. That's why they are called latching or maintained contact push buttons.
Push buttons are found in a variety of devices and applications, from remote controls and household appliances to industrial control panels. They can have different shapes and sizes, and some models may also have built-in lighting to indicate their state. These buttons are essential in designing user interfaces and are widely used to interact with electronic systems.
What is a Panel Push Button?
In reality, it is a push button installed on a panel. In this section, we have grouped only those push buttons designed to be mounted on a frame, chassis, or panel. There are other push buttons, such as those on printed circuits, for example, that, by functionality, would be located in the corresponding section, although the functionality is the same.
What is the Protection Rating or IP of a Push Button?
The IP proection rating of a push button, like other materials and/or components, is a classification indicating its resistance to water, dust, and other contaminants. It is measured according to the international standard IEC 60529, which uses a two-letter code to indicate the protection rating.
For example, a push button with an IP65 protection rating is protected against powerful water jets from any direction, even if the push button is in operation, and against dust entry.
The choice of a push button's protection rating is important to select the appropriate push button for a specific application. For instance, a push button to be used outdoors must have protection against water and dust.
What is an Emergency Mushroom Button?
An emergency mushroom button is a type of push button used to quickly stop a machine or process in case of an emergency. It is characterized by its mushroom shape, which facilitates its identification and operation by the operator.
These emergency buttons are used in a variety of applications, including:
- Industrial Machines: Used to stop the machine if a hazardous situation, such as a fire or explosion, occurs.
- Electrical Equipment: Used to interrupt the flow of current in case of a short circuit or electrical failure.
- Vehicles: Used in vehicles to stop the vehicle in case of an emergency.
Emergency mushroom buttons are usually designed to be operated with one hand, even with gloves. They often have a locking mechanism to prevent accidental activations.
They can be of two main types, based on their function and construction:
- Stop Mushrooms: Used to stop a machine or process.
- Disconnect Mushrooms: Used to disconnect the power supply to a machine or process.
Based on their construction, emergency mushroom buttons can be mechanical, operating through a mechanical mechanism, such as a lever or spring, or electric, operating through an electrical circuit, such as a pressure sensor or proximity switch.
Emergency mushroom buttons are an essential safety device that helps protect people and equipment in case of an emergency.
What is a piezoelectric pushbutton and what advantages or disadvantages does it have?
A piezoelectric push button is a type of switch or push button that uses the piezoelectric effect to generate an electrical signal when pressed. The piezoelectric effect is the ability of certain materials, such as quartz, to generate an electric charge when subjected to pressure.
These piezoelectric push buttons are commonly used in a variety of applications, including:
- Electronic Device Controls: Used to control the operation of electronic devices, such as TVs, radios, and computers.
- Alarms and Sensors: Used to activate alarms or sensors, such as smoke detectors or motion detectors.
- Musical Instruments: Used in musical instruments, such as guitars and pianos.
- Industrial Controls: Used in industrial applications, such as machines and equipment.
Piezoelectric push buttons have several advantages over other types of switches, including:
- Wear Resistance: They are highly resistant to wear, making them ideal for applications requiring a large number of actuation cycles.
- Corrosion Resistance: They are resistant to corrosion, making them suitable for applications in hostile environments.
- Small Size: They are very compact, making them ideal for applications where space is limited.
The operation of these buttons involves the following process:
- When the button is pressed, the pressure is transmitted to a piezoelectric element, such as a quartz plate.
- The piezoelectric element generates an electric charge in response to the pressure.
- The electric charge is sent to an electrical circuit, activating an output.
The output of the piezoelectric push button can be a digital signal, such as a voltage pulse, or an analog signal, such as a current or voltage signal.
These push buttons are available in different sizes, shapes, and colors and may also include features such as water, dust, and corrosion resistance.
Advantages and Disadvantages:
Piezoelectric push buttons have several advantages over conventional push buttons:
- Wear Resistance: They are highly resistant to wear, making them ideal for applications requiring a large number of actuation cycles. A conventional push button may wear out over time and stop functioning correctly, while a piezoelectric push button can last a long time.
- Corrosion Resistance: They are resistant to corrosion, making them suitable for applications in humid or corrosive environments. A conventional push button may corrode over time and stop functioning correctly, while a piezoelectric push button can last a long time, even in adverse environments.
- Small Size: They are very compact, making them ideal for applications where space is limited. A conventional push button may be large and bulky, making installation in confined spaces challenging.
However, piezoelectric push buttons also have some disadvantages, including:
- Cost: They are generally more expensive than conventional push buttons.
- Sensitivity: They can be sensitive to vibrations or shocks, leading to false activations.
- Temperature Resistance: They can be sensitive to temperature, causing operational issues in environments with extreme temperatures.
Overall, piezoelectric push buttons are a good choice for applications requiring a high number of actuation cycles, wear resistance, corrosion resistance, or a small size. However, they are more expensive than conventional push buttons and can be sensitive to vibrations, shocks, and extreme temperatures.
What are bounces in the electrical contacts of an electromechanical pushbutton and how to reduce them?
Bounces in the electrical contacts of an electromechanical pushbutton are undesirable phenomena that occur when the button is pressed or released. These bounces are rapid and uncontrolled fluctuations in the electrical connection that can generate multiple activation or deactivation signals in a short period.
When you press an electromechanical pushbutton, the switch contacts may close and open several times very quickly before stabilizing in a position. Similarly, when releasing the button, the contacts may bounce before settling in an open position. These bounces can cause issues in digital circuits, especially in applications where a clean and stable state transition is expected.
To reduce or eliminate bounces in the contacts of an electromechanical pushbutton, you can implement several techniques:
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Decoupling Capacitors: Adding a capacitor in parallel to the contacts can help smooth out transitions and reduce bounces. This capacitor can filter voltage fluctuations caused by bounces.
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Pull-Up/Pull-Down Resistors: Using pull-up or pull-down resistors on the button contacts can help stabilize the signal. These resistors connect the button contact to a known voltage level when not activated, preventing the signal from floating.
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Software Filtering: At the software level, you can implement algorithms that ignore state changes occurring in a very short time interval. This prevents bounces from having a significant impact on the system logic.
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Low-Bounce Switches: You can use buttons specifically designed to reduce bounces. These switches typically incorporate internal mechanisms or circuits to minimize bounces.
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Debounce Circuit: Implementing a debounce circuit can automatically filter out bounces. These circuits can be integrated into the electronic design to detect and eliminate unwanted transitions in the button signal.
The combination of several of these techniques can provide an effective solution to reduce or eliminate bounces in the electrical contacts of an electromechanical pushbutton, ensuring more reliable operation in electronic applications.