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When the countdown period has expired, the normally closed contacts of T300 become open, thus interrupting the logic continuity to the output Y400 and so Y400 is de-energised. During the countdown period, the output device Y400 remains energised by the latched path through the contacts Y400. Now, when X000 goes false, a true signal is sent to the timer to begin the countdown period. Thus, when the input X000 goes false, the output Y400 remains on, it is latched by its own contacts.
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This true state is fed back into the input to the normally closed contacts of the timer. In this example, when the input X000 is true, there is logic continuity through the normally closed timer contacts T300 to the output Y400. Upon the timer completing 10 s, the timer holding switch opens and the circuit opens, thus stopping the motor.ĩ.3.2.1 Sequential Control With Interlocks Upon passenger registering a request, the circuit gets closed, door motor starts, and timer also starts. The on delay counter is programmed for 10 s. The time required to open the lift door upon pressing the passenger request button is 10 s.
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When the counter becomes 0, parking full O/P becomes on, gate close output also becomes on, closing the gate and making the parking full flag input open, thus opening the circuit. Parking full flag, being NC, keeps the circuit closed and car entry input decrements the counter every time a car enters. Īs long as the number of cars in the parking lot is less than 50, the counter O/P is OFF.Entry of every car decrements the counter. īoth start and stop I/P switches are momentary types in actionĮxample 2: Car door open alarm generation functionĪny one or more doors getting opened (I/Ps becoming on) and car key I/P in enabled state (on), activate cabin lamp O/P and buzzer O/P (becoming on).Įxample 3: Parking full indication and closing the gate.When stop I/P switch is momentarily pressed, O/P M gets disabled (becomes OFF), resets its flag M, and gets de-latched (stays OFF). When start I/P switch is momentarily pressed, O/P M gets enabled becomes on), sets its flag M, and gets latched (stays on)