Selection of PLC

Yes PLC The basic parameters of , The specific selection can be carried out through Siemens' selection software

Download address ：TIA Selection Tool | Fully integrated automation | Siemens CNhttps://new.siemens.com/cn/zh/products/automation/topic-areas/tia/tia-selection-tool.html

Catalog

1. Determine sensor type , Draw flow chart

2. Determine how many digital ports and analog ports are needed

3. choice PLC type ,1200 etc. 1500 etc. , Select the expansion module based on the selection tool

4. According to the numerical quantity （DI/DO） And analog quantity （AI/AO） Add corresponding expansion modules .（ Pay attention to the allowance ）

5. Choose the power supply , Memory card （ Generally, it doesn't need to be too big 4M Enough ）

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1. Determine sensor type , Draw flow chart

This step is mainly to sort out the operation mode of the system and the action process of each switch , Determine what type of sensor is needed , How many sensors are needed . How many switches and loads are needed 、

2. Determine how many digital ports and analog ports are needed

name	model	Number	what is needed I/O	Input and output	voltage	AC and DC
Speed control
System general start button		1	I1	Input	24V	Direct
The system always starts the indicator		1	O1	Output	24V	Direct
The motor 1 Start button		1	I1	Input	24V	Direct
The motor 1 Stop button		1	I1	Input	24V	Direct
The motor 1 Running indicator light		1	O1	Output	24V	Direct
The motor 1 fault （ Self detection of frequency converter ） Indicator light		1	O1	Output	24V	Direct
Flow detection
（ Two position tee ） Solenoid directional valve control button		1	I1	Input	24V	Direct
（ Two position tee ） Solenoid directional valve control relay coil		1	O1	Input	24V	Direct
（ Two position tee ） Solenoid directional valve position indicator		1	O1	Output	24V	Direct
（ Three position cross ） Solenoid directional valve control button		2	I2	Input	24V	Direct
（ Three position cross ） Solenoid directional valve control relay coil		2	O2	Input	24V	Direct
（ Three position cross ） Solenoid directional valve position indicator		2	O2	Output	24V	Direct
Proportional relief valve 1 Enable end		1	O1	Output	24V	Direct
Proportional relief valve 2 Enable end		1	O1	Output	24V	Direct
Distance adjusting oil pump 2 Start button		1	I1	Input	24V	Direct
Distance adjusting oil pump 2 Stop button		1	I1	Input	24V	Direct
Distance adjusting oil pump 2 Running indicator light		1	O1	Output	24V	Direct
Distance adjusting oil pump 2 Soft start indicator		1	O1	Output	24V	Direct
Distance adjusting oil pump 2 fault （ Thermal relay ） The signal		1	I1	Input	24V	Direct
Motor fault indicator		1	O1	Output	24V	Direct
Soft start fault signal 1、2、3		3	I3	Output	24V	Direct
pump 2 Soft start intermediate relay coil		1	O1	Output	24V	Direct
pump 2 Full voltage start intermediate relay coil		1	O1	Output	24V	Direct
Soft start intermediate relay coil		1	O1	Output	24V	Direct
High temperature alarm indicator of oil distributor		1	O1	Output	24V	Direct
Liquid level monitoring
Liquid level relay signal		1	I3	Input	24V	Direct
Liquid level indicator		3	O3	Output	24V	Direct
Oil supply pump 3 Running indicator light		1	O1	Output	24V	Direct
Oil supply pump 3 Start button		1	I1	Input	24V	Direct
Oil supply pump 3 Start relay coil		1	O1	Output	24V	Direct
Oil supply pump 3 Stop button		1	I1	Input	24V	Direct
Oil supply pump 3 fault （ Thermal relay ） The signal		1	I1	Input	24V	Direct
Oil supply pump 3 fault （ Thermal relay ） Indicator light		1	O1	Output	24V	Direct

The following parts can be found in Siemens' selection software TIA Selection Tool In the middle of , You can output reports , Contains detailed information .

3. choice PLC type ,1200 etc. 1500 etc. , Select the expansion module based on the selection tool

Siemens 1500 Type of PLC Than 1200 More expensive , It is also more powerful .

Input and output ports according to the required digital quantity DI/DQ And analog input and output ports AI/AQ Configure the device , You can use Siemens' own selection software .

 

 

4. According to the numerical quantity （DI/DO） And analog quantity （AI/AO） Add corresponding expansion modules .（ Pay attention to the allowance ）

Check the address 、 Sensor output （ voltage +-5V Or current 0-10mA）, Pay attention to the settings AI/AO The measurement type of the corresponding channel matches the output signal of the sensor . Some channels can only accept voltage signals .

As for the difference between voltage and current , It has been said in sensor selection , Strong anti-interference ability of current signal , But the wiring is more complicated , To put PLC Series incoming circuit , And the voltage signal wiring is more convenient .

For temperature sensors , Use thermistor （RTD） Or thermocouples （TC）

5. Choose the power supply , Memory card （ Generally, it doesn't need to be too big 4M Enough ）

About relay type Rly And transistor type DC Explanation ：

AC/DC/RLY, representative AC220V Power input ,DC24V I Terminal input , Relay Q Terminal output .

DC/DC/DC, representative DC24V Power input ,DC24V I Terminal input , The transistor Q Output

About

（1） The overload capacity of transistor is less than that of relay ： Generally speaking , When there is a large impulse current （ For example, light bulbs 、 Inductive load, etc ）, The overload capacity of transistors is small , More derating is needed .

（2） Under rated working conditions , The relay has action times and service life , Only aging transistors have no limit on the number of uses ： Relay is a mechanical component, so it has action life , Transistors are electronic components , Only aging , There is no limit on the number of uses . The switching times per minute of the relay are also limited , Transistors do not .

（3） Load voltage 、 Current type different load type ： Transistors can only carry DC loads , And the relay brings 、 DC load is ok . electric current ： Transistor current 0.2A-0.3A, Relay 2A. voltage ： The transistor can be connected to DC 24V（ Generally, the maximum is DC 30V about , The relay can be connected to DC 24V Or exchange 220V.

（4） Transistors respond faster than relays ： The principle of relay output type is CPU Drive relay coil , Make the contact pull , Make the external power supply drive the external load through the closed contact , Its open circuit leakage current is zero , Slow response time （ about 10ms）.

（5） Different load capacities ： The capacity of transistor with load is less than that of relay with load , When using transistors , Sometimes we need to add other things to drive a large load （ Such as relay , Solid state relay, etc ）.

The principle of transistor output type is CPU The transistor is turned on and off by optical coupling , To control the external DC load , Fast response time （ about 0.2ms Even smaller ）. Transistor output is generally used for high-speed output , Such as servo ／ Stepping, etc , For output with high action frequency ： Such as temperature ＰＩＤ control , Mainly used in stepper motor control , There is also servo control , There is also solenoid valve control （ The action frequency of the valve is high ）. Transistors are mainly used for positioning control , Use the output of the crystal to send out pulses . And the relay cannot be used to send pulses , You can't position control . If you use relays to control positioning servo or stepping, you need to add positioning modules , Economically uneconomical . And with a transistor output, you can control servo, etc .

Nowadays, customers use transistor output + There are many intermediate relay schemes .