What are Microswitches?
These are inexpensive parts that can function for a very long time, with some of them being rated to endure as many as 10 million cycles before they break down. The switches are used in a variety of different applications, but their main characteristics being easily actuated and incredibly durable make them common in consumer devices, industrial applications and other uses where they endure many cycles over their lifespan.
These switches are very commonly employed as safety devices, as they are reliable, inexpensive and can open up a circuit when needed, preventing a machine from being turned on or a door from closing when someone is in the way.
How Do Microswitches Function?
Essentially, in any application where the amount of voltage that a load is receiving needs to be varied on the fly, a variable transformer is likely employed.
What are the physical principles applied within a variable transformer?
Many microswitches have a construction that employs a wheel stationed above a push-button actuator. The actuator is depressed, lifting a lever that move the contacts into the desired position. Most of these switches are momentary switches. This means that, once the actuator is released, the switch returns to its normal state. This is accomplished by way of springs. The springs keep the actuator in position and the contacts in their normally closed or opened position. When depressed, a weaker flat spring in the device moves the contacts, but is moved back into place when the switch is released.
Microswitches make a distinctive clicking noise when they are actuated, This can provide tactile feedback for testing the switch. The internal mechanisms are simple enough, and secure enough in their casings, that they can be installed in very demanding environments and still function reliably. To further guarantee performance, specific materials may be chosen for the contacts and the switches can be chosen based on their ability to repel the intrusion of environmental hazards, which is described below.
These switches are usually provided with a couple of holes on the case that are used to fasten them to whatever surface or appliance is required. The switches are commonly small, rectangular components, completely self-contained, that require no maintenance. Their low cost makes it easy enough to replace them when they wear out, which happens rarely, at best.
Microswitches will be differentiated by their normal state, the number of poles and throws that they have and the type of case that they are situated in. There are designs that are intended to be used on printed circuit boards and designs that can be fastened into place with a hex nut. The compact size and reliability of these components means that there are many varieties, as there are many uses for microswitches.
Microswitches are also differentiated by their electrical characteristics. These are small devices and generally only designed to carry low current and voltages. There are designs that are intended to be used in more demanding applications, however.
What Are the Characteristics of Microswitches?
Microswitches are very common electrical components and there are many variations on the design. Depending upon their use and what type of conditions they will endure during use, various characteristics have to be taken into account.
What Type of Applications Need Microswitches?
Microswitches are very common devices. They are used in consumer devices, industrial equipment and more.
One of the most common applications for these devices is in door interlocks. These are common in consumer devices, notably in microwave ovens, where the door has to be shut before the power to the device will turn on.
Microswitches are also used in leveling devices, such as those used on vending machines. In an elevator, these devices are used in the door as a safety switch. The devices are also used to detect whether paper is jammed in a copier and for myriad other purposes.
Microswitches can be designed to be very sensitive. Such designs can be used in very precise equipment, such as that which measures the flow of air or other gasses through a system. They can also be used to detect pressure and temperature.
These devices are used extensively in industry, often in control circuits. They are sometimes employed as the direct means of turning equipment on and off, as well.
What Are the Characteristics of Microswitches?
Microswitches are very common electrical components and there are many variations on the design. Depending upon their use and what type of conditions they will endure during use, various characteristics have to be taken into account.
Actuator Type
This is simply the type of actuator that actually throws the contacts in the device. There are many different types. Button actuators are very popular, as are lever types. There are variations on the broad types, such as long hinge levers, long leaf levers and long straight levers being variations on lever actuators. There are also roller designs, spring designs and more.
Contact Configuration
The contact configurations for these switches are like any other switch. They include normally open and normally closed designs with various pole and throw configurations available.
Contact Current Rating
This is a measure of the amperage that the contacts can carry. While most of these switches are used at lower current levels, there are designs that are intended to be used in higher current applications, such as for the actual controller for an electric motor or another device.
Terminal Type
Microswitches offer flexible installation options and, owing to their size, they can be used on printed circuit boards. The terminal type options are appropriately broad. They include lugs, PCB mounts in various angles, screws and more. Some of the mounts are designed to be soldered into place.
IP Rating
IP Rating stands for Ingress Protection Rating. This is a measure of how well the device is protected from intrusion. The ratings apply to everything from body parts to specific substances, such as water and other chemicals. This rating system is designed to be a bit more specific than just saying that a switch is weatherproof or describing it with some other vague term.
For example, the liquid ingress protection on a device can be specified as being appropriate for conditions where there is dripping, splashing, spraying or jetted water. This allows the designer to be sure that the device they're selecting is suitable for the conditions under which it will operate.
FAQ on Microswitches
- What is the operating force? This is usually measured in Newtons. It describes the amount of force required to actuate the switch.
- What is the release force? This is the force the switch exerts when releasing, also measured in Newtons.
- What are the contact materials? The contact material on microswitches can be chosen based on durability requirements or any other requirements that drive the decision. Materials include gold, silver, brass, nickel and various alloys of the above. There are also options for different materials to be used in the stationary and moving parts, as well as options as to whether the material is double clad.
- What is their operating life? Where microswitches are concerned, the operating life of the equipment is generally very high, being measured in millions of cycles, in most cases. Consumer products generally have lighter-duty microswitches than industrial products, but the low cost of these parts makes it easy enough to upgrade to higher mechanical life expectancies when required or when it's simply beneficial to do so.
- What is the case material? Microswitches are durable, in part, because their cases can be made out of very sturdy materials. Fiberglass and other materials are common for the construction of these switches. Specialty materials such as Nitrile can be used in applications where it is required. In areas where shock and vibration may be an issue, materials such as rubber can be selected. Materials such as steel and zinc are also widely available, though most of the manmade materials are durable enough for most applications.
- What are Microswicth Actuators? The actuator is the means by which mechanical force is applied to the switch to make it change state. These come in many different designs, from buttons to levers and more. These are generally chosen based on what type of actuator will work best with the appliance or machinery to which the switch is attached. For instance, on a car door, a button actuator works well, as the closed door can depress the button and change the state of the microswitch so that an alarm is switched off and so forth.
- What Are Microswitch Boots? A switch boot is placed over the actuator and other parts of the switch to prevent the ingress of materials or for identification purposes. They can be color-coded to indicate that the switch is part of a specific circuit or system. They can also be outfitted with colored boots to make the switch easier to locate.
- What Are Microswitch Caps? A switch cap is much like a boot. It goes over the top of the actuator, providing protection and an easy means of identifying the switch.
- What Are Microswitch Hex Nuts? Hex nuts are threaded onto the microswitch to hold it in place. They are particularly good solutions for switches that are mounted below a surface with the actuator protruding above. They provide an easy means of securing the switch and, when needed, they are easily removed.
- What Are Microswitch Levers? The lever on a microswitch is used to trigger the actuator. They are available in various designs and sizes, so they can be used in most any application where the switch needs to be made easier to trigger.
- What Are Microswitch Terminal Covers? Terminal covers provide a means of insulating the switch against being exposed to potential contaminants. They also provide a means to protect the terminals from being accidentally shorted and from accidently coming into contact with operators, potentially causing a shock.
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