Questions about PLC control, two questions about PLC?

There is a program written inside the PLC, which is pre-written, and when the input meets the program writing conditions, the output signal is sent to the output to realize the control of the field device. The normally open contact of the thermal protection switch is the PLC input signal terminal, which should be an alarm signal, when the thermal relay is closed, it means overload, but it depends on the PLC's internal programming to know that it is output to that point.

The coil end of the contactor is measured with a pen, and the live signal is connected to the live wire when we press the switch, whether the bolt is issued by the PLC to connect with the neutral line, and the contactor is connected after the circuit is connected, and the load is energized?

It doesn't have to be the output of the PLC to be contactor closed. It's just that the load is energized and the contactor is engaged.

The PLC determines the output signal according to the internal programThe PLC outputs only a switching signal, and there is no electricity!

There are two commonly used types of PLC output ports: 1. Relay unit, which is the same as the output of ordinary relays, which is equivalent to a contact of the relay, and the connection method is flexible, which is not certain; 2. Transistor unit, the connection method is generally the open collector output, as you said, the "live wire" (to be exact, it should be low-voltage positive electricity, generally 24V) passes through the coil of the contactor, and connects it to the ground when the PLC outputs.

PLC is programmable logic control, which is a kind of controller that can be programmed using a computer.

Designing a conventional circuit requires buttons, takes time relays, intermediate relays. To design complex circuits, analog controllers and intelligent controllers are also required. After using PLC, these problems can be easily solved, eliminating the need to design complex external circuits, and can also easily realize the control of the equipment on the touch screen and computer.

PLC can control lights, cylinders, solenoid valves, motors, servos, steppers, encoders, etc., which are widely used in industrial control.

1. About the granary conveyor belt system:

io Allocation Table Design:

io address.

Type Io.

Description. Enter the Start button.

Enter the Stop button.

Output M1 motor start quiet signal.

Zheng lead slag outputs M1 motor stop signal.

Output M2 motor start signal to answer.

Output M2 motor stop signal.

Note: When the start button is pressed, the state is 1, the PLC enters the program, the M1 motor starts, and the output is 1;

After a delay of 5 seconds, the M2 motor starts and outputs 1;

When the stop button is pressed, the state is 1, and the M2 motor stops, and the output is 1;

After 5 seconds of delay, the M1 motor stops and outputs 1;

If the start button is pressed again, the program starts again.

2. About the parking lot:

Input Output signal name.

Signal type. Signal description.

Start button Input When the start button is pressed, the parking lot starts to run the stop button Input When the stop button is pressed, only the entrance and exit of the parking lot are allowed Vehicle detector Input Detects whether there is a vehicle arriving at the entrance.

Exit Vehicle Detector Input Detects if a vehicle has arrived at the exit.

Entrance Railing Control Outputs Controls the raising and lowering of the entrance railing.

Exit Railing Control Output Controls the raising and lowering of the railing at the exit.

Green light at the entrance Output Controls the green light at the entrance.

Entrance Red Light Output Controls the turn of the red light at the entrance.

I only gave the I o allocation table here.,I don't have time for the rest for the time being.,I'll have time to make up for you.。

What is PLC?

What are the applications?

Summary. Hello dear, as follows:

1. Fault modeling. Specifically, it refers to the gradual establishment of a mathematical model of system faults according to the relationship between prior information and input and output, and uses this as the basis for fault detection and diagnosis.

2. Fault detection. Fault detection can be used to determine whether a running system will fail from a range of measurable or unmeasurable estimated variables, and if a problem occurs in the system, an appropriate alert will be issued.

3. Separation of faults. When a system fails, the first choice is to give the location of the source of the fault, and then distinguish whether the cause of the fault comes from the actuator, sensor or the controlled object.

4. Fault classification, evaluation and decision-making. When the fault is accurately judged, it is necessary to deeply analyze the severity of the fault, the impact of the system and the trend of development, and take different measures through different situations.

Why is PLC control happening.

Hello dear, as follows: 1. Fault modeling. Specifically, it refers to the gradual establishment of a mathematical model of system failure according to the relationship between prior information and input and output, and takes this as the basis for fault detection and diagnosis.

2. Fault detection. Fault detection can try to determine whether the running system will fail from the measurable or unmeasurable estimated variables, and if the system has a problem, it will issue a corresponding alarm. 3. Separation of faults.

When a system fails, the first choice is to give the location of the source of the fault, and then distinguish whether the cause of the fault comes from the actuator, sensor or the controlled precursor object. 4. Fault classification, evaluation and decision-making. When the fault is accurately judged, it is necessary to deeply analyze the severity of the fault, the impact of the system and the trend of development, and take different measures through different situations.

1. CPU abnormality: When the CPU is abnormal and the CPU alarms the ant, you should check all the devices connected to the internal bus of the CPU unit. The specific method is to replace the units that may cause failures in turn, find out the faulty units, and deal with them accordingly.

2. Memory abnormality: When the memory is abnormal alarm, if it is a problem with the program memory, the fault will be reproduced after reprogramming. In this case, it may be that the interference of noise causes a change in the program, otherwise the memory should be replaced.

3. Abnormal input and output units, abnormal expansion units: when this kind of alarm occurs, the insertion state of the input and output unit and the connector of the extension unit should be checked first, the cable connection state, and a unit after determining the fault occurs, and then replace the unit. 4. Do not execute the procedure

The input check is identified by an input LED indicator or by an input monitor consisting of a writer. When the input LED is not lit, it can be preliminarily determined that the external input system is faulty, and then cooperate with the multimeter to check the object.