How and where to install the limit switch

Precautions for using limit switch

一. The use of switches

1, inductive load: power factor above 0.4 (AC) time constant below 7ms (DC)

2, lamp load: constant current 10 times the load of surge current. Motor load: 6 times the constant stray surge current load.

(1) Ambient temperature: 5 ~ 35℃

(2) Ambient humidity: 40~70%RH

(3) The limit switch shall be fastened on the mounting plate and mechanical equipment, and shall not shake.

(4) The position of the installation time limit switch must be accurate, otherwise it cannot reach the purpose of position control and limit.

(5) Check the limit switch regularly to avoid bad contact and reach the purpose of stroke and limit control.

Limit switch selection

(1) Select the type according to the application situation and control object.

(2) According to the force transmission and displacement relationship between the machine and the limit switch, select the appropriate operating head form.

(3) Select the series according to the rated voltage and rated current of the control circuit.

(4) Select the protection form according to the installation environment.

二, mechanical attention

Regarding operating force, stroke and contact characteristics, the figure shows the relationship between operating force → stroke → contact force. To ensure high reliability, it must be used within the proper range of contact forces. When using a normally closed circuit (NC), the operator must be set so that the drive lever can return to the free position. In addition, when using the normally open loop (NO), the pressure must be 70 to 100% of the specified value of the overrange (OT) (60 to 80% of the total stroke (TT)) to absorb small swings and · The contact may become unstable when the stroke is set near the action position (OP) and return position (RP). Also, if in the total stroke position (TTP), the drive rod and switch body may be damaged by the inertia of the operating body, so use the mounting plate and operating body to adjust the stroke. Change in force (contact force). When set near OP and RP, the contact force becomes unstable and cannot ensure high reliability.

In addition, resistance to vibration and shock is weakened.

If the drive rod is often depressed, it will cause initial failure and poor reset. Maintain and replace it regularly. As for the mechanical conditions at the time of selection, the drive rod must be selected according to the operation method. · Please confirm the running speed and frequency.

1, when the operation speed is very slow, the switch of contact will be unstable, easy to lead to poor contact or fusion welding and other problems.

2, the operation speed is very fast, the impact of the action may damage the switch. If the frequency is too high, the contact may not be switched in time, please do not exceed the specified frequency. · Do not exert excessive force on the drive rod. Damage or poor movement may occur. · Please set the travel within the appropriate range for each model. If used outside range, the switch may be damaged.

三, electrical attention

Electrical conditions for type selection

Ac and DC switch capacity is very different, please use within the rated range. In the DC case, the control capability is extremely low.

This is mainly because it does not have a zero point (current crossing) like AC. Arc once produced, it is difficult to disappear, arc time is longer. And the direction of the current is fixed, so there will be contact migration phenomenon, contact can not be broken because of uneven. ·× will produce reverse induced voltage under induction and other conditions. The higher the voltage, the greater the energy, the greater the contact loss and migration, so please use within rated conditions. · Use microloaded products in the case of microvoltages and currents. Using common silver-based contacts may reduce contact reliability