Buttons are commonly designed as biased switches, although even some unbiased buttons incorporate a spring to return to their unpressed state. A biased switch is often referred to as a momentary switch, where pressing the button momentarily activates the circuitry to be in either the "on" state or the "off" state.
These different states of a push button are known as the "push-to-make" mechanism or the "push-to-break" mechanism:
Push-to-Make Mechanism (Normally Open): In this mechanism, the button acts like a normally open switch. When the user presses the button, it makes contact with the circuit, allowing current to flow. However, the moment the button is released, the switch breaks the current flow in the circuit. A typical example of a push-to-make mechanism is a keyboard key. When you press a key, it completes an electrical connection momentarily.
Push-to-Break Mechanism (Normally Closed): This mechanism operates in the opposite way of the push-to-make. When the button is pressed, the switch breaks contact with the circuit, interrupting the flow of current. Upon releasing the button, it makes contact with the circuit again, allowing current to flow once more.
Push-buttons find a wide range of applications across various industries and devices. Some typical uses of push-buttons include:
Calculators: Push-buttons are used in calculators for inputting numbers and performing mathematical operations.
Kitchen Appliances: Push-buttons are found in kitchen appliances like microwave ovens, where they allow users to select settings, start, stop, or pause cooking processes.
Mechanical and Electronic Devices: Push-buttons are essential components in mechanical and electronic devices, serving as user interfaces for functions like power control, mode selection, and data input.
Mechanical Locks: Some mechanical locks use push-button mechanisms for entry, requiring a specific sequence of button presses for access.
Push-Button Telephones: Traditional push-button telephones use buttons to dial numbers and initiate calls.
Emergency Buttons: Push-buttons serve as emergency stop buttons in various industrial and commercial settings, providing a quick way to halt machinery or processes in emergency situations.
In commercial and industrial environments, push-buttons can be interconnected through mechanical linkages. When one button is pressed, it can force the release of another button. This interlocking mechanism is commonly used in situations where a "start" button must be released by pressing a "stop" button. An example of this is the emergency stop button in standby generators, which ensures immediate shutdown in case of emergencies.
Color coding is often applied to push-buttons to associate specific functions with certain colors, reducing the risk of users pressing the wrong button. Common color codes include red and green, with red typically indicating a "stop" function, and green indicating a "start" function. Red push-buttons, often designed with large heads or mushroom heads, are frequently used as emergency stop buttons to enhance safety and comply with electrical regulations.
In terms of configuration and switch type functions:
Normally Open (NO): The contacts of a normally open switch are disconnected or open in their normal, unactuated position.
Normally Closed (NC): The contacts of a normally closed switch are connected or closed in their normal, unactuated position.
Switch type functions can vary:
Maintained Contact: In this type, the actuator (button) stays in the thrown position until manually reset.
Alternating Contact: This switch has an alternating action, such as a push-on and push-off functionality.
Momentary Contact: The switch must be held in the actuated position, and it returns to its normal position once the actuating force is removed. This is commonly used for functions like pressing a button to temporarily activate a device.
These push button mechanisms are fundamental in various applications where momentary electrical control is required, such as in keyboards, push-button switches, and many other control devices. They allow for precise control and are commonly used in scenarios where a simple "on" and "off" function is needed by the user.
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