A detection switch is a type of switch connected to other circuit components to detect the parameters of the component or circuit (such as current, voltage, etc.). The detection switch has an induction function, and the main body is usually various induction switches or proximity switches, which require an external power supply to work D3C detection switch

1 Contact output type

The switch elements output are the contacts of microswitches, limit switches, and relays. The main purpose is to connect with electromagnetic switches, small motors, electromagnetic devices, etc., and can be used for switching control of several amperes of current. When connecting to electronic control equipment, attention should be paid to vibration time and minimum load current

2. Optoelectronic coupling output type

The electrical insulation of the detection circuit is used in the same way as the contact output type.

. A switch that can control a current of 10 to 50mA 3. DC 3-wire type

a When detecting the voltage output type, output a voltage signal to the load. The voltage output type is mainly manufactured for the purpose of connecting electronic control equipment composed of transistors or ICs such as electronic counters and contactless relays B Current output type

can also be referred to as open, collector output type. When the output transistor operates, there are NPN type (current absorption) for suction current and PNP type (current source) for discharge current. If a small capacity power transistor is used in the output transistor, it can switch a current of 50-200mA and directly drive loads such as electromagnetic relays, solenoid valves, DC solenoids, and display lights

4. DC 2-wire type

The proximity switch in this method has 2 wires. Therefore, when using it, attention should be paid to polarity. Not only can the use method be the same as mechanical limit switches, but the wiring is also simple, but the following conditions should be noted.

Even if the switch is in the closed state, current needs to be supplied to the detection circuit of the proximity switch. For this reason, there is a small amount of current flowing in the load. This current is called leakage current. When leakage current occurs, a "leakage current" is generated at both ends of the load × The load is also the cause of initial failures during use. The occurrence time of initial faults varies depending on the manufacturing method and cannot be generalized. Generally, they occur within one week to 10 days after the start of use

(1) Occasional faults

include faults caused by poor semiconductor components, such as broken wires, short circuits, insufficient capacity of resistors and capacitors, circuit breakage of circuit boards, and soldering materials, but the occurrence rate is extremely low.

. When the proximity switch frequently malfunctions, it can be considered as a problem with the operating environment

(2) Load short circuit and wiring error

When a load short circuit is caused by wiring error or live working, it causes a large current to flow to the detection switch and the output circuit to burn out.

. As a protective measure outside the detection switch, the method of cutting off the fast short-circuit current can be used, and the fuse can be used for protection, which not only protects the load short circuit, but also has a protective effect on the ground wire. However, due to the small residual capacity of the output transistor inside the switch, the effect of 100% cannot be achieved

(3) Damage caused by interference waves