1. Contact output type
The switch element with micro switches, limit switches, and relay contacts as output, connected to electromagnetic switches, small motors, electromagnetic devices, etc. as the main purpose, can be used for switching control of several amperes of current. When connecting with electronic control devices, attention should be paid to vibration time and minimum load current.
2. Optoelectronic coupling output formula
The method of using the detection circuit electrical insulation is the same as that of the contact output type. A switch that can control a current of 10-50mA.
3. DC 3-wire type
a. Voltage output type
When conducting testing, output a voltage signal to the load. Voltage output type is mainly manufactured for the purpose of connecting electronic control devices composed of transistors or ICs such as electronic counters and contactless relays.
b. Current output type
Also known as open, collector output type. As shown in Figure 8, when the output transistor operates, there are NPN type (current absorption) that draws in current and PNP type (current source) that discharges current. By using small capacity power transistors in the output transistor, it is possible to switch between 50-200mA current and directly drive loads such as electromagnetic relays, solenoid valves, DC solenoids, and display lights.
4. DC 2-wire type
The proximity switch of this method has 2 wires, so if polarity is taken into account during use, not only can the usage method be the same as mechanical limit switches, but the wiring is also simple. However, the following conditions should be noted.
(1) 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, a small amount of current flows in the load. This current is called leakage current. When there is leakage current, the occurrence of "leakage current x load" at both ends of the load is also a cause of initial faults during use. The 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.
(2) Occasional malfunction
This includes faults caused by defects in semiconductor components, such as broken or short circuits in resistors and capacitors, insufficient capacity, circuit board circuit breakage, and the presence of solder, but the occurrence rate is extremely low. When the proximity switch frequently malfunctions, it may be due to environmental issues. Please consult the manufacturer.
(3) Load short circuit and wiring error
When the load short circuit is caused by wiring errors or live work, a large current flows to the detection switch, causing the output circuit to burn out. As a protective measure taken outside the detection switch, the method of cutting off the fast short-circuit current can be used, which is protected by a fuse. This not only protects the load from short circuits, but also has a protective effect on the ground wire. However, due to the small residual capacity of the output transistor inside the switch, it cannot achieve a 100% effect.
(4) Damage caused by interference waves
The damage caused by interference waves is gradually formed, so it is extremely common for damage to occur one or two to three months after the start of use. Therefore, when damage occurs during this period, the cause can be determined as interference waves. The instantaneous erroneous action of the detection switch during the opening and closing of the inductive load is caused by interference waves.
