Micro Switch Structure and Characteristics Explanation
1. The five components of the micro switch
(1) Transmission parts: the force or stroke from the outside to the internal mechanism. (2) Quick acting mechanism components: the use of high quality conductive spring or shrapnel, the execution of quick action. (3) Contact parts: really open or close the electrical circuit. (4) Terminal components: connection with the external circuit. (5) Housing parts: good insulation, high mechanical strength, protect the internal mechanism.
2. Quick action mechanism of the micro switch
According to the conversion time of switch from NC end to NO end and from NO end to NC end, the conversion sensitive switch is usually less than 10ms and the contact bounce time is less than 5ms. (Test speed of 0.6mm/s)
The basic function of the switch appliance is to be able to divide and close the circuit in the required short period of time, that is, the role of the so-called switch. The mechanical switch gear is to use the contacts to open the circuit current. When the circuit is opened in the atmosphere, as long as the voltage exceeds 12 to 20V, the current to be opened more than 0.25 to 1A, in the contact gap (also known as the arc gap ), usually a cloud of extremely high-temperature and near-cylindrical gas emitting a strong light is produced, which can conduct the electricity, which is the arc.
The current is not broken until the arc is extinguished and the contact gap becomes an insulating medium. The arc occurring in the micro switch equipment is referred to as the switching arc. The switching arc phenomenon, that is, the arc burning and extinguishing process, is the most important content of switch appliances. Arc is a free gas with high temperature and high conductivity, which has great destructive effect on the contact and shorten the life of the switch.
3. Micro gap of micro switch
What is a reasonable gap? Here is the definition in GB15092:
The so-called contact gap is relatively small, that is, the gap must meet the functional requirements of the switch, mainly the electrical strength and insulation resistance of the switch must meet the standard requirements, including the switch in high and low temperature, wet environment, after the assembly of guests such as wave welding conditions.
(1) Strong current switch, different current levels, use different gap levels, industry experience value is as follows:
a. For 10A/16A current grades, the gap is 0.45 to 0.70mm.
b. For 22A/26A current grades, the gap is 0.75 to 1.0mm;
c. For especially humid environment conditions, such as G5 faucet switch, switch clearance design is 1.0 to 1.5mm; Avoid water vapor entering the switch to form a current path between contacts;
d. When the switch is used in the power tool industry such as lawn mower, electric drill, etc., directly control the safety switch of the power supply. The contact gap must be greater than 3mm to prevent the formation of a path between the contacts under vibration conditions, which will affect the safety. Our G5L series belongs to this kind of switch;
(2) What damage does too small a gap do to the switch function?
When the switch is switched on, it is easy to produce "pull arc". If the gap is small, the switch contacts cannot be electrically "disconnected", then in the process of rapid conversion, the contact of switch will produce serious heat, and heat is transferred to the terminal, so that the terminal temperature rises, melting the rubber case, causing the early failure of the switch. As a result, life becomes shorter.
4. State and parameter definition of micro switch (with specified stroke and force)
Definition of action, position and force: The switch has 4 position states, 3 force manifestations and 4 action strokes.
5. Housing of micro switch
The switch housing is usually consist of a rubber case, a rubber cover and a button. The rubber case is used to fix and support the current carrier metal parts and plays an insulating and protective role. The rubber case cover usually covers the current carrier metal parts to play an insulating and protective role. The last one belongs to the operating parts and stimulates or transmits the movement of the internal mechanism.
The rubber case is used to fix the terminal in the design. The creepage distance and electrical gap of the switch should meet the requirements of GB15092.
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