I. Advantages and disadvantages of reed relay Advantage Fully sealed contacts, strong environmental adaptability The reed is sealed in a nitrogen-filled glass tube, which is dustproof, moisture-proof, corrosion-proof, not easy to oxidize, and stable for long-term working contact of humid and dusty equipment. Very low drive power consumption The power of the coil is only 0. 1 ~ 0.5 W, and the I/O port of the microcontroller can be directly driven without the need for transistor amplification. The action speed is fast Pull-in time is 0.1 ~ 1ms, suitable for high frequency and high speed signal switching. Strong weak signal switching capability Gold-plated contacts, stable contact resistance, micro-ampere level small voltage/small current signal will not appear poor contact, mostly used for precision measuring instruments. The insulation performance is excellent High withstand voltage between coil and contact, very small leakage current, suitable for insulation detection, high voltage quarantine scenarios. Compact size Under the same voltage specification, the size is smaller, and there is a SMD micro model, which saves PCB space. Extremely long mechanical life Without complex mechanical transmission, the mechanical life can reach 1 billion times. Shortcoming The current carrying capacity of the contact is poor Normally, it can only switch 0.1 ~ 2A small current, and can not control high-power loads such as lamps, solenoid valves, motors and so on. Weak shock and impact resistance Violent vibration can easily cause contact misconnection and misdisconnection. Susceptible to external magnetic field interference The surrounding magnet and high-power coil will cause misoperation, so the layout should be far away from the magnetic device. Very poor arc resistance Power failure with inductive load is easy to produce arc, which can easily cause permanent damage of contact adhesion. Hysteresis of reed The strength of the magnetic field will affect the pull-in and release thresholds, so the voltage margin should be reserved in the design. II. Advantages and disadvantages of conventional electromagnetic relay Advantage The load capacity is strong It can achieve 5A, 10 A, 16 A or even larger current, and can directly drive lamps, heaters, solenoid valves and small motors. Better vibration resistance and external magnetic field resistance With iron core shielding and independent spring transmission structure, it is not easy to malfunction in industrial vibration environment. Greater resistance to arc The size of the contact is large, and the inductive load and the AC load are not easy to adhere and burn. The specifications are complete There are DC, AC, high-power, high-voltage, multi-contact and other rich models, with strong versatility. Cost advantage (high-power scenario) When controlling large current, the cost performance is much higher than that of the reed relay. Shortcoming The contact is exposed and easy to oxidize Contacts exposed to the air, humid, dusty environment will be blackened for a long time, and small signals are prone to poor contact. Slow motion Pull-in 5 ~ 20 ms, cannot be used for high frequency fast switching. Coil power consumption is too high Generally 0.5 ~ 2 W, most of them need to be driven by triode/optocoupler, and can not be directly connected to the pins of MCU. Weak signal switching difference After contact oxidation, the micro-current circuit is prone to open circuit and signal instability. Complex mechanical structure and short service life Relying on the linkage of armature, bracket and spring, the electrical life is generally tens of millions of times, which is much lower than that of dry spring. Larger volume at the same power The internal transmission mechanism occupies space, and the miniaturization is not as good as the dry spring.