What is the Principle of a Timer?
The timer is a time-keeping device. It was a patent applied for by the British surgeon Soga in 1876. The appearance of the timer has brought tremendous changes to our lives.
According to the different input conditions, the timer can be divided into five types: on-delay timer, off-delay timer, hold on-delay timer, pulse type timer and extended pulse timer. kind.
Among them, the on-delay timer is also called the SD timer, which is the most basic one in PLC (programmable logic controller); the off-delay timer is also called the SF timer. When the input condition is OFF, it will play a delay effect;
The hold type on-delay timer is also called SS type timer. When the input condition is ON, it will play a latching function. If the input condition changes from ON to OFF, the input condition is still considered to be ON to hold effect;
Pulse type timer is also called SP type timer. When the input condition is ON, it will act immediately, but the action is pulse type and can only maintain the set time of the timer. After the set time, even if the input condition is ON, The timer is also in the OFF state. If the input condition becomes OFF within the set time, the action will stop;
The extended pulse timer is also called the SE timer. It is similar to the pulse timer. The difference is only that when the input condition is ON, even if the condition turns OFF within the set time, the action will not stop. Until the set time.
When the timer input conditions meet the timing requirements, start timing, the set value register stores the set time value unchanged, the current value register stores the current time value changes with time, once the current time value increases to the same as the set time value, timing The device acts, the normally open contact is connected and the normally closed electric shock is disconnected, and the program acts on the controlled object to achieve the purpose of controlling time.
