Application of AND circuit and NOT circuit
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Application of AND circuit and NOT circuit

Posted Date: 2024-02-04

1. Working principle of subway door signal lights

When the subway arrives at a station, the doors on one side of the platform open at the same time, and the door signals light up at the same time. After getting in and out of the car and the bell stops, the door is closed. At this time, the door signal lights of the compartments whose doors are not completely closed are still on. When all the doors are completely closed and the door signal lights go out, the confirmation indicator light on the driver's console lights up. This is a scene we often see in the subway.

The picture shows the structure diagram of the subway door signal light.

There is contact a on one side of the door. When the door is opened, contact a is disconnected and contact b on the other side is connected, lighting the door signal light. After the door is closed, the door signal light goes out and the main circuit is connected. In this way, the door closing confirmation indicator light on the driver's console will light up only when all the doors are closed.

For the series contact circuit shown in the figure, the input status of switches A and B and the on and off status of the indicator light can be summarized in Table 1. The circuit that completes this action is called a logic and (operation) circuit or an AND circuit.

Action Input Output A B L a 0 0 0 b 0 1 0 c 1 0 0 d 1 1 1

The relationship between the subway door switch and the door closing confirmation indicator light on the driver's console forms a complete AND circuit.

2. The relationship between the car door and the interior lights

The interior light of a car is composed of three circuits: ① turn off the light, ② keep the light on, and ③ flash. Here we introduce the flashing circuit.

When the door is opened, the push rod installed at the corner of the door pops out, forming a closed circuit and lighting up the interior lights. The interior lights come on regardless of which door is open or when both doors are open. On the contrary, as long as all the doors are not closed, the interior lights will not go out.

It can be seen from the figure that when switch A is turned off, the coil of the electromagnetic relay is not excited, so the contact X- of the electromagnetic relay is closed, so the lamp is lit. When switch A is closed, the electromagnetic relay is energized and excited, contact X is disconnected, and the light goes out.

The circuit that completes this action is called a NOT (arithmetic) circuit or NOT circuit. The table is the truth table of the NOT circuit. The relationship between the car door switch and the interior light is an application of the NOT circuit.

Action Input Output A B a 0 1 b 1 0 Review Editor: Huang Fei
#Application #circuit #circuit