限位开关是非常小的机器，使机器能够停止、启动或改变方向。它们可以确保系统安全并平稳运行，无需人工帮助。
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在本指南中，您将了解六种主要类型的限位开关以及如何选择合适的限位开关。
限位开关在工业控制系统中起着至关重要的作用。它们就像传感器一样，可以识别机器的运动或位置变化，因此作保留在航程内。
限位开关是一种小巧但功能强大的设备，用于机器和控制系统。它有助于检测机器零件何时到达特定位置。触发时，它会打开或关闭电路以发送信号。这些开关有多种设计，适用于接触式和非接触式作。
安全需要限位开关。它们能够防止机器损坏、超程并精确调节它们。由于这些开关可以自动引导机器，因此人为错误也被最小化。它们提供了额外的安全元素，有助于简化流程。
限位开关适用于许多行业。这些是制造、汽车、包装和机器人技术。您还可以在电梯、传送带、数控机床和其他类似应用中使用它们。
它们与各种设备兼容，并且由于其灵活性而在不同的环境中运行良好。当涉及到种类繁多的解决方案时，像 Xurui Switch 这样的制造商会创建特殊型号来满足他们的特定需求。
以下是 6 种类型的限位开关;
这种类型的开关有一个柱塞，当接触时，该柱塞被推入。它还广泛应用于需要直线运动检测的电梯、门和机器。柱塞激活内部触点以启动或停止功能。这些安装简单，非常适合垂直运动。
滚轮杆开关通过旋转臂进行机械作，旋转臂末端有一个轮子（滚轮）。当物体经过时，它会压在滚轮上，完成开关。它与传送带或自动化装配生产线完美配合。当需要检测侧向运动时，首选这些开关。
旋转开关检测旋转运动而不是直线运动。它们通常应用于起重机、起重机或大功率齿轮驱动组件。开关进入一个位置，表示在旋转特定次数时停止或改变。它们非常适合以控制为导向的电动设备。
这些开关包含一根又长又细的杆（类似于胡须）。轻轻触摸杆，使其弯曲并激活开关。他们擅长处理输送机上的易碎部分或轻质物体。这种类型非常适合对压力敏感的产品。
接近开关不需要接触即可工作。相反，它们使用磁性或红外光来感知物体。它们非常适合潮湿、多尘或爆炸性环境。它们提供更长的使用寿命，因为不会发生物理磨损。
微型限位开关体积小，响应速度快。它们灵敏准确，应用于电子、电器和机器人领域。他们以低力量打开，并负责重复性职责。这最适合紧凑和精密的安装。
请按照这些选择正确的;
考虑物体的运动。它是推动、滑动、转动还是按压？柱塞开关适用于制造，而旋转开关适用于旋转零件。始终将开关与机芯相匹配。不匹配可能会导致故障或磨损。
某些情况很严重。如果存在灰尘、湿气或振动，请选择密封开关。在这里，接近开关很好，因为它们不与任何东西接触。IP 级交换机在恶劣环境中更安全。
并非所有开关都能处理相同的电压或电流。检查系统的需求。确保开关在正常使用时不会过载或烧坏。查看触点配置并确保与您的控制系统兼容。
有些开关体积庞大;其他的则很小。如果空间紧张，请选择微动开关。此外，确保开关能够承受按下多远和按下多少次的力。通过正确放置安装座可以防止与振动相关的问题。
了解变化将帮助您做出更明智的决定。每种类型都有其优点和缺点。
机械开关需要物理接触。接近开关等非接触式开关不通过接触方式运行。您所接触的环境越干净、越安全，决策就越好。机械开关的维护可能会增加。
根据任务的大小及其敏感性做出决策。精密驱动系统中也有灵敏度。
开关的使用寿命更长，因为它们采用非接触式设计，不会磨损。机械部件可能需要提前清洁和更换。然而，它们往往更便宜。想想长期储蓄。考虑价格和更换它的可能性。
以下是要避免的事项以及如何纠正它;
机械开关会随着时间的推移而磨损。这可能会导致接触不良或火花（电弧）。吸引优质零件并持续监控它们将帮助您避免事故。如果电弧是经常遇到的问题，请切换到非接触式或密封版本。
当开关未正确插入时，它可能无法正常工作。或者更糟糕的是，它可能会在错误的时刻自行激活。确保其正确安装并且不会随着时间的推移而漂移。安全的安装和校准可以防止这种情况发生。
每个开关都不是为了抵抗灰尘或湿气而设计的。请务必记住查看 IP（入口保护）等级。举个例子，等级为 IP67 的开关据称是防尘防水的。如果您的预算较低，请购买保护套。
作不正确的开关可能会导致故障或人员伤亡。购买前查看规格。考虑负载、速度和移动类型。应始终识别制造商信息并查阅制造商的数据表。
这些做法使您的设备使用寿命更长。
使用正确的螺钉和支架安装交换机。将其与移动部件对齐。对其进行几次测试以确认它在正确的时间启动。校准使其准确。
注意是否有任何磨损、生锈或松动的电线。五分钟的检查可以节省数小时的维修时间。将其置于每周或每月的维护程序中。维护检查簿。
当您的开关有移动部件时，请经常清洁它们。使用吸水毛巾或低气流。使用少量润滑剂后，应涂抹少量润滑剂，以防止吸引灰尘。过度使用润滑剂可能会导致堆积。
使用正确的电线并避免电路过载。识别标签。它使安全诊断和维护系统变得更加简单。利用接线图。
以下是不同类型在多个行业的使用方式。
经常使用滚轮杆和柱塞开关。它们会在物品经过时检测它们，并帮助引导或停止传送带。它们提高了效率并减少了人为错误。通过正确的对齐可以避免停机。
CNC 机器需要精确的开关。微型开关和接近开关效果最佳。它们帮助机器在切割或雕刻过程中确定其精确位置。快速响应时间是这里的关键。
旋转开关是电梯的标准配置。柱塞类型在包装系统中工作，以检测物品何时到达下一阶段。这些有助于保持安全和顺畅的流动。
接近开关是最好的，因为它们保持清洁和安全。即使被灰尘或油覆盖，它们也能工作。如果密封良好，机械开关也可以工作。根据耐用性和危险风险进行选择。
限位开关可能很小，但它们是巨大的贡献者。他们监控工厂系统、家用电器，并使一切安全、智能和高效。始终使用正确的柱塞、旋转或接近类型，具体取决于您的具体需求。
了解您的需求，审视您的空间，并从长远考虑。通过这种方式，您的机器将保持有效和安全。如果维护得当并使用正确的开关，您应该会提高生产率并减少故障。
A limit switch is an electro-mechanical device used to send an electrical signal based on a physical interaction. Limit Switches are used to detect the presence of objects, thus allowing the system to take desired action.
Limit Switches can be found in a number of everyday devices:
Countless limit switches are found in manufacturing. They are used as control devices and safety devices for machinery and personnel. In all cases, the limit switches will send a digital signal to the control system. Based on the hardware and software tied to said switches, the system is able to take appropriate action.
Limit switches are an inexpensive way to create a link between the physical and electrical domains. They have been developed a number of decades ago and the mass adoption of their use significantly lowered their cost for the end user. They thus play an important role in manufacturing due to their simplicity and low cost.
Limit switches can be classified into four main types based on the type of actuator:
In addition to the type of actuator, limit switches can also be classified by their electrical configuration. The two most common electrical configurations are:
Some limit switches also have a double throw (DPDT) electrical configuration, which means that they have two sets of electrical contacts, one NO and one NC. When the actuator is activated, the NO contacts close and the NC contacts open.
Limit switches are available in a wide variety of sizes, shapes, and materials to meet the specific needs of different applications. They are also available in a variety of electrical ratings, so that they can be used to control a wide range of loads.
Here are some examples of how different types of limit switches are used in real-world applications:
Limit switches are a versatile and reliable way to control and monitor machines and processes. They are used in a wide variety of industries, including manufacturing, construction, agriculture, and transportation.
As discussed above, a limit switch is used to translate a change in mechanical state into an electrical signal. How does the device actually accomplish that?
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A limit switch is a simple device. The lever is used to close a contact within the switch. When the contact is closed, it allows the electrical signal to go through. The mechanical operation is similar to that of a light switch. However, a spring is added to return the limit switch into its original position.
The critical parameter of a limit switch is at which point it closes the contact within. This parameter will vary between switch types as well as brands. It is important to verify the datasheet to confirm this position. It will influence the system design that will utilize the limit switch.
As discussed previously, once the actuator is displaced a certain distance, the switch is made. At this point, it needs to transmit a signal to an electrical device which may be a Programmable Logic Controller (PLC), relay, control circuit, or an additional limit switch. A limit switch is similar to a relay in the sense that it can be purchased in one of the following configurations:
There is an argument to be made for either configuration. However, when it comes to limit switches being used for safety purposes, it’s always advised to have current circulating in “resting state”. This is important as during a problem in the circuit, the safety should trigger. Should it be set to no-power in the “resting state”, the circuit may fail to prevent injury or damage.
In this section, we’re looking at the Allen Bradley 801 General Purpose Limit Switch configurations. Below, you’ll find the “Contact Arrangement” provided by the manufacturer. Let’s review each section in detail
A - Normally Open (NO) limit switch symbol.
B - Normally Closed (NC) limit switch symbol.
AC - Alternating Current Ratings for light duty limit switches at different voltage levels. It is important to remember that although your application may require a switch to operate within a 24VDC circuit, it’s possible to use these across multiple industries in which voltage level standards are different.
DC - Direct Current Ratings for light duty limit switches.
C - Normally Open (NO) and Normally Closed (NC) set of contacts on a single limit switch.
H - Dual Normally Open (NO) and Normally Closed (NC) set of contacts on a single limit switch.
N - Dual Normally Open (NO) set of contacts on a single limit switch.
O - Dual Normally Closed (NC) set of contacts on a single limit switch.
In the first example of a limit switch we had reviewed, there was a single position at which the switch would trigger the signal. In this case, there are two points at which the signals will be different. These signals can be picked up in discrete logic, but most commonly, this would be done using a PLC. A PLC programmer can utilize such a limit switch to detect a difference between a partial and a full limit switch closure.
Position of Lever = OFF
Position of Lever = Partially Closed
Position of Lever = Fully Closed
Until now, we’ve talked about limit switches that would actuate the same one way or the other. This is the case for most general purpose limit switches. However, it is possible to detect if the switch was pushed in one way or the other through the interlock present in the differential location limit switch. The operation will be as follows.
Position of Lever = OFF
Position of Lever = Closed to the Left
Position of Lever = Closed to the Right
The Normally Closed (NC) variation of the previous switch will operate as follows. The only difference is the state of the contacts in the “Off” position.
Position of Lever = OFF
Position of Lever = Closed to the Left
Position of Lever = Closed to the Right
This variation of a limit switch features four contacts. Two of these contacts can be used as Normally Open (NO) connections and two other as Normally Closed (NC).
Current ratings for regular duty limit switches. Note that these ratings are higher than the ones found in Section 1.
A limit switch is an electromechanical device that consists of an actuator mechanically linked to an electrical switch. When the actuator is moved by an object, it causes the electrical switch to open or close, depending on the type of limit switch.
There are two main types of limit switches: normally open (NO) and normally closed (NC). An NO limit switch is open when the actuator is not activated, and closes when it is activated. An NC limit switch is closed when the actuator is not activated, and opens when it is activated.
Limit switches are used in a wide variety of applications, such as:
Here is a simplified explanation of how a limit switch works:
Here is an example of how a limit switch is used in a real-world application:
A conveyor belt is used to transport products from one area of a factory to another. A limit switch is installed at the end of the conveyor belt to detect the presence of products. When a product reaches the end of the conveyor belt, it activates the limit switch. The limit switch then sends a signal to a controller, which stops the conveyor belt. This prevents the product from falling off the conveyor belt.
A limit switch used in manufacturing is rated for hundreds of thousands of cycles. However, there are various flavors of this device that aren’t as robust for other everyday applications.
Elevator systems commonly require limit switches for a variety of purposes by building codes. They are used for position detection, safety and operational state of the elevator. The types used in this application are rated for an even greater number of cycles as they constantly experience actuator movement through the life of the system.
Limit Switches are used in everyday appliances: fridges, tea kettles, mixers, washers, dryers and more. The limit switches in these appliances are the same in principle, but different in reliability. In other words, they operate the same, but may fail much faster then their manufacturing counterparts.
Using a basic ohmmeter or Digital Multimeter (DMM), it’s possible to determine whether or not a limit switch is bad. Disconnect the limit switch from the system and apply the ohmmeter leads to each terminal. If the limit switch is normally open (NO), the resistance should be very high. If it’s normally closed (NC), the resistance should be close to zero. Toggle the limit switch into the active position and measure the resistance. It should be the opposite in this setting. If the transition does not occur, the limit switch is bad.
When a limit switch fails, it can either remain stuck open (not allowing the circuit to close) or stuck closed (always completing the circuit). This can cause issues such as:
If you suspect a faulty limit switch, test it with a multimeter and replace it if needed.
No, running a furnace without a high-limit switch is dangerous. The limit switch is a safety device that prevents overheating by shutting down the burner if temperatures exceed safe levels. Removing or bypassing it could result in:
If your furnace limit switch is malfunctioning, it should be replaced rather than bypassed.
No, a limit switch is not a relay, though both control electrical circuits. The key differences:
However, in some applications, limit switches work alongside relays to control motors, actuators, and other devices.
To reset a manual furnace limit switch:
For mechanical limit switches used in automation:
The primary difference lies in function and operation:
They are often used together in industrial automation, where a limit switch detects position and a solenoid valve controls a process.
A solenoid is used instead of a mechanical switch when:
The cost of replacing a solenoid switch depends on the type and application:
If replacing a solenoid, always verify compatibility with your system to avoid additional expenses.
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