Micro switches types are essential components in sensing and control instruments. These instruments are vital in various machinery, be it industrial, agricultural, transportation, construction, etc.
Unlike devices like proximity switches, this component is quite simple. But its uniqueness lies in the ability to perform snap-action switching with precision. Because it is critical in multiple applications, here is a close-up look at the micro-switch types and other details about the device.
A micro switch is a precise snap-action change-over switch containing a tiny contact gap. Also known as a snap-action miniature switch, the snap action refers to a change-over where the breaking speed and contact-making are independent of the actuator's operating speed.
After making physical contact with an object, a micro switch's contacts change state. When the mount pin plunger switch is in the rest/released position, the NO (Normally Open) circuit opens. On the other hand, the NC circuit (Normally Closed) closes and can carry current.
However, when the plunger depresses or switches, current flows in the NO circuit, and the NC circuit opens.
A micro switch has the following features.
Building a micro switch is simple. It requires only the following parts.
These switches come in various types, including the following.
Flexible rod micro-switches can operate in any 360° direction, except the one running along the rod's center. It detects shape/direction inconsistencies effectively and has a small operating force. Additionally, the actuator absorbs the overtravel, creating a substantial leeway in object play operation.
This device features a rotating low-torque actuator. It is perfect for detecting lightweight objects such as paper currency.
With its changeable lever shape to match the operating body, this switch is suitable for low-speed, low-torque cam operation. The lever material is usually steel.
This switch is similar to a reverse operation hinged lever but with a roller attached. It is also suitable for cam operation.
This switch features a bend in the lever to create a large stroke. It is ideal for detecting moving objects, such as dogs and cams.
A powerful leaf spring gives this device a large stroke, making the actuator ideal for cylinder drives or low-speed cams. Also, it features a fixed bearing point, so the overtravel must be within the application's specifications to avoid damage.
This device is similar to a leaf spring but with a roller attached. It is ideal for dog or cam operations.
A micro switch with a hinged lever bent at the end to a curve for use as a simple roller type.
While the simulated roller lever contains a hinged lever, this one features a leaf lever. This lever has its end bent to a curve for use as a simple roller type.
Pin plungers are ideal for short & direct strokes (perfect for high-precision position detection). However, the downside is having the shortest overtravel of any actuator. Therefore, it requires a reliable stopper.
Although it has the same applications as the pin plunger, the spring pin type has a longer overtravel. Also, the plunger diameter is a bit larger, but avoid the off-center loads when using the device.
Contrary to the "short" word in its name, this switch has a long overtravel, like with the spring pin plunger. But it has a short plunger with a large diameter for easier alignment.
A hinge-lever is ideal for a low-speed, low-torque cam. Usually, the lever is steel-made, and you can alter its shape to match the operating body.
This device is a hinge lever with a roller attached and is suitable for high-speed cam operation.
Mounted to a panel by a hexagonal nut and lock nut for positional adjustment, panel mount pin plungers offer the largest overtravel of all the plunger types. You can operate the device manually or mechanically and use it with a low-speed cam.
This plunger is similar to the panel mount pin type but with a roller attached. However, it has a shorter overtravel, and you can operate it using a dog or cam. Also, you can get cross-rollers running parallel to the switch.
Consider the following factors when selecting a micro switch.
There are various actuator types. They include a push-button, roller, pin, or lever. When considering this factor, think about how long or short (big or small) you want the actuator. You have the option of picking one of the following:
Will you be using AC or DC power supply, and at what voltage? Also, what is the largest current the contacts will have to handle? Each micro switch type has current and voltage specifications, and you should ensure these match your application requirements.
Usually, micro switches contain one NC and one NO contact, but you can get more.
It is vital to note that the number of movable contacts in the switch determines how many poles you need. Similarly, the number of fixed contacts determines the required throws.
The switch's outer cover should withstand the environmental factors in its operational area. Ensure it has the necessary IP or NEMA rating to withstand explosions, water, etc.
A micro switch has the following advantages.
The contact and actuator's movement and speed are independent. Therefore, you can rely on the terminals changing state predictably unless the switch is almost at the end of its lifespan.
In other switches, the actuator's movement causes the contacts to move. However, contacts in a micro switch do not change state until the actuator gets to a specific reset/trip point.
A micro switch has high switching speeds that extinguish arcs quickly. This fast movement minimizes arcing damage to the contact surfaces.
An electrical arc
There are two ways to use a micro switch.
The switch is in NC (Normally Closed) mode with an unpressed lever. Therefore, the movable contact (lever terminal C) connects with the NC terminal, allowing the current to flow in this circuit. However, there is no contact between C and NO.
But when you press the lever, terminals C and NO connect because the lever pushes the movable contact down to touch NO. Therefore, the current will flow in this circuit, but NC will be open.
You can use the SPDT micro switch separately or simultaneously (in NC or NO mode) as per the application.
Although micro switches do not require user maintenance, you should keep them clean and paint-free, especially in the actuator area. Besides that, regularly check how secure the mounting is and monitor the switch actuator-to-actuating medium relationship.
Remember, the switching action causes arcing, so avoid installing the switch in areas with explosive gasses. Also, do not lubricate or use chemical/aqueous cleaning fluids on the device. Lastly, avoid dropping or disassembling the unit because this can cause damage, shock, or burning.
If soldering the switch, avoid overheating the insulation part. It is advisable to use a heat shunt to prevent this issue. The insulation is vital between the micro-switch and metallic plates because it increases the clearance on open terminals. But for optimum mechanical strength, wrap the conductor around the terminal's tip to avoid the occurrence of loose wire strands.
With side mounting, place the switch on a smooth, flat, firm surface and fasten it using the recommended screw size. Do not enlarge the mounting holes, and you can use epoxy resin for additional security.
The overhead panel in the airplane simulator
In short, micro switches are simple devices with numerous applications in several industries. However, they come in various types, and you should pick the one with the right features for the job. We hope this article will make it easier to choose the most suitable device, and if you have any questions or comments, leave a message in the chat/contacts section.
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