How to choose PLC input/output modules？
(1) Select voltage level: Depending on the voltage, there are DC 5V, 12V, 24V, 48V, 60V and AC 110V, 220V;
(2) According to the form of protection, it can be divided into two types: isolated and non isolated.
(3) Choose module density: divided into 8 points, 16 points, 32 points, and 64 points based on the number of points.
High density modules, such as 32 or 64 points, with the number of connection points depending on the input voltage and ambient temperature. Generally speaking, the number of simultaneous connection points should not exceed 70% of the total number of modules.
(4) Design considerations for backup input points
When designing the total number of input points, there is a certain margin. The allocation of these backup points should be considered separately for each input module, preferably allocated to each set of input points. For example, an input module has 32 input points, with 8 points per point forming a group. In the design, 8 points are reserved as a backup point. Once the remaining 7 points fail, the system can only be restored to normal by changing the wiring from the fault point to the backup point and modifying the corresponding address. This is beneficial for modifying system design and handling faults.
2. Selection of Digital Output Modules
(l) Selection of output mode
(2) Selection of output power
When selecting a module, be aware that the output power provided in the manual is greater than the actual power required by the load. In practical applications, if the load requires too much power, the digital output module cannot meet the demand. At this point, there are two design approaches:
Use an intermediate relay and drive the coil of the intermediate relay with a digital output.
Drive the load in parallel with multiple digital output points. At this point, it is important to pay attention to the consistency of actions across multiple output points.
(3) Load
Given the load situation, two points should be noted:
For loads such as electromagnetic brakes, although the load current is small, the number of turns is high, and the reverse voltage is very high when the power is cut off, sometimes causing the output transistor to reverse breakdown. At this point, capacitors and resistors should be connected in parallel at both ends of the load to suppress reverse voltage;
For lamp loads, pay attention to starting the pulse current. The starting current is generally 10 times the rated load current. When driving the lamp load, the corresponding output power is given in the manual.
3. Selection of Analog Input Modules
(1) The input range of simulated values.
The analog input module has various input ranges, including 0~10V, 10V, 4~20 mA, etc. Some products utilize external input range submodules to achieve various input ranges, allowing the same analog input module to adapt to different input ranges; Some products also make various modules with different input ranges into independent analog input modules.
(2) The numerical representation of analog values.
The function of the analog input module is to convert analog values into binary values. Pay attention to the conversion accuracy when selecting.
(3) Sampling cycle time.
The sampling time reflects the response time of the system in processing analog inputs.
(4) The external connection method of the analog input module.
There are various external detection components with different signal ranges and required connections. The analog input module can provide various connection methods to meet these requirements, including the connection methods of resistors, thermocouples, and various sensors. Sometimes it also includes two wire and four wire connections with compensation, which should be selected according to actual needs.
4. Selection of Analog Output Modules
(1) Output range and output type.
The analog output range includes 0~10V, 10V, and 4~20mA. The output types include voltage output and current output. There are generally two types of output for analog modules, but the connection method when connecting loads is different.
(2) Requirements for load.
The main requirement for the load is the load impedance, and the maximum load impedance is usually given in current output mode. In voltage output mode, provide the minimum load impedance.
5. Selection of Intelligent Input/Output Modules
Intelligent input and output modules are different from general input and output modules, as they have microprocessor chips, system programs, and memory. The intelligent interface module is connected to the CPU module through the system bus and works independently under the coordinated management of the CPU module, improving the processing speed of the factory and facilitating application. The general intelligent input and output module includes communication processing module, high-speed counting module, analog control module with PID regulation, valve control module, etc.
Popular models：
EA9-T15CL
3BHB030310R0001
3704Е
3504Е
CMA140 3DDE300420
P154.R4 REV 8
PCU-DPIO V4.6.3
705-1512-01
8111
3504Е
8440-1860D
5SNG015045P0301
USIO21
CI871AK01 3BSE092693R1
WRC1021D
BIPC-300047-01
8206-TI-IS-02
VT-HNC100-1-23/W-08-P-0
XV-102-D8-70TWR-10
IS420UCSBS1A
BUM60-A-SM-0110-B
CI871AK01 3BSE092693R1
IC697CPX928
PM866AK01 3BSE076939R1
EM940 M34372
JANCD-JMM01-1
SH30703P01A2000
G761-3263
G122-829-001
24765-01-01
65UV5-1000
H201Ti
PR6426-000-130
PR9268/601-000
NBRA-669C
PR6423/003-030+C0N021
HMS02.1N-W0028-A-07-NNNN
PP865 3BSE042236R1
PIB-701A
MVME162-014（3.2E版或者3.3E版本）
RET316
REL316
SPM-D11 8440-1706
BUS623-20/30-54-M-207
5275306860
