Types and Functions of Limit Switches
Sun, Mar 28 by ATO.com
- Introduction of limit switch
Limit switch is a kind of sensor to detect and control the mechanical movement beyond the limit displacement. For example, the position limiter of electric rolling shutter gate ensures that the motor will stop working when the gate is opened or closed to the specified position, so as to ensure that the motor and mechanical components will not be damaged due to excessive work. The commonly used limit switches include all kinds of travel switches, micro switches, and photoelectric switches. In short, as long as the corresponding detection device is equipped and the functional requirements are completed, they can be used as limit switches.
- Application function of limit switch
Limit switch is widely used in all kinds of machine tools and lifting machinery to control its travel and carry out terminal limit protection. In the control circuit of the elevator, the travel switch is used to control the speed of opening and closing the car door, the limit of automatic opening and closing the door, and the upper and lower limit protection of the car. There are many applications of limit switch and many electrical appliances have its shadow. So what can such a simple switch do? It mainly plays the role of interlock protection. The most common example is its application in washing machines and tape recorders.
- The speed of the washing machine is very high in the process of dehydration (drying). If someone inadvertently opens the door or cover of the washing machine and then reaches in, it is easy to cause harm to people. In order to avoid this kind of accident, an electric contact is installed on the door or cover of the washing machine. Once someone opens the door or cover of the washing machine, it will automatically cut off the power of the motor, and even make the door or cover open by mechanical linkage, and immediately "brake" to force the rotating parts to stop, so as to avoid personal injury.
- In tape recorders and video recorders, we often use fast forward or rewind. The tape rotates rapidly, but it stops automatically when it reaches the end of the tape. Here, the travel switch is working again, but this time it is not caused by collision but by the sudden increase of the tension of the tape. The limit switch is mainly used to change the mechanical into electrical signal, so that the running state of the motor can be changed, so as to control the mechanical action or as program control.
- The real use of limit switch is in industry, where it cooperates with other equipment to form more complex automation equipment. There are many such limit switches on the machine tool, which can control the movement of work piece or the stroke of automatic feed to avoid collision accidents Sometimes limit switch is used to make the controlled object automatically change direction between two specified positions, so as to obtain continuous reciprocating motion. For example, when the automatic material transportation car reaches the terminal, it touches the limit switch and turns on the dumper mechanism, then it overturns the materials in the car and returns to the starting point. After arriving at the starting point, it touches the travel switch of the starting point to connect the circuit of the charging mechanism and start the automatic loading. If it goes on like this, it becomes a set of automatic production line, which needs no human management and works day and night, saving people's physical labor.
- There are various limit switches for you to choose from ATO
- There is a waterproof limit switch for industrial occasions requiring oil resistance, water resistance and dust prevention. There are different types of actuator for waterproof limit switch, such as roller plunger, roller lever, top plunger and coil spring. It contains two contact switches 1NO+ 1NC and can be used in the environment temperature -25~+70℃ (-13~+158℉). Waterproof limit switches apply to AC-15, 5A/250VAC, 3A/125VAC. Other rated current/voltage is customizable, such as 0.4A/125VDC, 0.2A/250VDC, etc.
- At present, it is widely used in large transport machinery, loading and unloading machinery and other heavy equipment. It is a heavy limit switch with detachable roller rod, cast steel shell and 1nc contact switch. Heavy duty limit switch can be used in the automation control system with voltage AC 0-500V/25~60Hz or DC 0-440V, and environment temperature -30~+120℃ (-22~+248℉).
- All kinds of high temperature limit switches: high temperature limit switch with roller lever, high temperature limit switch with adjustable roller lever, high temperature limit switch with roller plunger, high temperature limit switch with top plunger, high temperature limit switch with coil spring, high temperature limit switch with adjustable rod and high temperature limit switch with fork lever.
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