Q1: Does the PLC output not have a power supply? For example, if I want to control a 110V relay, do I need to add a power supply? How do I wire it?
A: The PLC's output port is merely a switch to drive the load; it doesn't have its own power supply. If you want to control a 110V relay, you need to add a power supply. The PLC's output is connected to the relay's coil, and the relay is also connected to a 220V AC power supply. The PLC's COM terminal is also connected to a 220V AC power supply.
Q2: Why are there no X8 or X9 addresses for the input port?
A: The input and output relays of the Maixin PLC are addressed in octal, so they can only be X0-X7, and there is no X8 or X9. The address after X7 should be X10.
Q3: Does the PLC output circuit need to be equipped with a fuse?
A: A fuse needs to be added to the PLC output circuit because if the load experiences a short circuit or fault, it can easily burn out the contacts or transistors, and also burn out the printed circuit board where the output circuit is located. Therefore, a fuse that provides short-circuit protection needs to be added to the load circuit.
Q4: How should a PNP three-wire proximity switch be connected to the input port of an MX3U PLC?
A: Connect the signal output terminal of the PNP three-wire proximity switch to the PLC's input port, such as X0. Connect the 0V terminal of the PNP proximity switch to the 0V terminal on the PLC. Also, short-circuit the S/S terminal with the 0V terminal. Connect the +24V terminal of the PNP proximity switch to the 24+ terminal on the PLC. If using an external 24V power supply, connect the signal output terminal of the PNP three-wire proximity switch to the PLC's input port, such as X0. Connect the 0V terminal of the PNP proximity switch to the negative terminal of the external 24V power supply. Also, short-circuit the S/S terminal with the negative terminal of the external 24V power supply. Connect the +24V terminal of the PNP proximity switch to the positive terminal of the external 24V power supply.
Q5: The scan cycle of a PLC is fixed. How do I know if my program exceeds the inherent scan cycle? What methods are there to find out, and how can I extend the scan cycle?
A: If you want to know the current scan cycle, you can read it directly from the PLC's special register D8010; if the PLC has a special memory that can be used to set a constant scan cycle, then you only need to set a specified value in this special memory to change the scan cycle time.
Q6: Does "MOV K0 K2Y0" mean to reset Y0-Y7? Then why does "MOV K1 K2Y0" only set Y0 instead of Y0-Y7?
A: K2Y0 in the instruction is a combination bit element, representing Y0-Y7. The MOV K0 K2Y0 instruction sends 0 to K2Y0, which actually sends a binary number. The binary number of 0 is B 0000 0000, so it resets Y0-Y7. The MOV K1 K2Y0 instruction sends 1 to K2Y0. The binary number of 1 is B 0000 0001, so it sets Y0 to 1, rather than setting all of Y0-Y7.
Q7: Why does the system display "soft component settings are incorrect" when I input T1K20 in the ladder diagram?
A: When you input T1K20 in the ladder diagram, it displays "Soft component setting incorrect" because there is no space between T1 and K20. There is no specified number of spaces, but at least one space is required. The correct input method is: OUT T1 K20. Note that there must be a space between OUT and T1, and between T1 and K20. When inputting timer instructions, also be careful not to confuse the letter O with the number 0.
Q8: For example, if X001 controls T5 and T5 has a delay of 50 seconds, does X001 need to be turned on for 50 seconds before T5 will activate? Or is it enough to just turn on the X001?
A: X001 needs to be on for 50 seconds before T5 will activate. This is because X001 is the timer's driving condition, while T5 is a general-purpose timer. When the driving condition X001 is deactivated, the timer will reset and stop counting.
Q9: I have an MX1N-40MR PLC with several COM terminals on the output side (Y side): COM1, COM2, COM3, COM4, COM5. How do I use them? Which Y terminals do they correspond to?
A: Because the output loads include contactors, relay coils, solenoid valve coils, indicator lights, horns, etc., the power supply characteristics of various loads may be different. In order to accommodate different load power supplies, the PLC divides the output terminals into several groups. The load power supply of the same group of ports is the same, and the ports of different groups can be connected to different power supplies.
The MX1N-40MR has a 4-point common terminal, meaning each of the four output points shares a common terminal. This is called a 4-point common terminal. The correspondence is as follows: COM1 is the common terminal for Y0-Y3, COM2 is the common terminal for Y4-Y7, and so on.
Q10: What is the purpose of those black dots on the input/output terminals?
A: The black dots on the input/output terminals are empty terminals left to fit the overall structure of the PLC. They are not internally wired and are useless terminals. No wiring is required. Empty terminals cannot be used as wiring terminals; doing so will interfere with the PLC.
Q11: What is the programming cable model for the MX series PLC?
A: The programming cable for the MX series PLC is either SC-09 or USB-SC09-MX. SC-09 is for connecting to the computer's serial port. USB-SC09-MX is for connecting to the computer's USB port.
Q12: What does [D<= D150 H0] mean in Maixin PLC?
A: [D<= D150 H0] is a contact comparison instruction. The "D" in front indicates that this instruction is a 32-bit contact comparison instruction. It compares whether the value of the 32-bit number (D151, D150) is less than or equal to 0. If the condition is met, the contact is closed; otherwise, the contact is opened.
Q13: What does [D<= D108 C251] mean?
A: [D<= D108 C251] is a contact comparison instruction. The "D" in front indicates that this instruction is a 32-bit contact comparison instruction. It compares whether the value of the 32-bit number (D109, D108) is less than or equal to the current value of the counter C251. If the condition is met, the contact is closed; otherwise, the contact is opened.
Q14: In Maxim PLC programming, should the set and reset instructions be used together?
A: In Maxim PLC programming, set and reset instructions do not necessarily have to be used together. Only the set instruction can appear, or only the reset instruction can appear, or they can be used in pairs.
Q15: If the external input signal X0 is input 10 times in 1 second, is it necessary to use a high-speed counter?
A: Does the need for a high-speed counter determine the PLC's scan cycle? The frequency of the counter's input pulse signal cannot be too high. If more than one pulse signal is input within a scan cycle, the remaining pulse signals will not be counted by the counter. This will cause inaccurate counting. Therefore, there are certain requirements for the frequency of the counter's input pulses. Generally, the pulse signal period should be greater than twice the scan cycle to ensure that no counts are missed.
When the external input signal X0 is input 10 times within 1 second, the PLC's scan cycle should ideally be within 50ms. If it exceeds 100ms, it is best to use a high-speed counter.
Q16: In the following program...
(MOVP K2 D0)
(MOVP K4 D1)
(DMOV D0 D2)
The program's third line, below D0 and D2, shows the number 262146. How did this number come about?
A: Because (DMOV D0 D2) is a 32-bit transfer instruction, this instruction transfers the data from (D1 D0) to (D3 D2). The result of executing the previous two transfer instructions is that D0 is K2 and D1 is K4. In fact, the internal binary number of D0 is B0000 0000 0000 0010, and the internal binary number of D1 is B0000 0000 0000 0100. Therefore, (D1 D0) is actually B0000 0000 0000 0100 0000 0000 0000 0010. The decimal number corresponding to this 32-bit binary number is 262146.
Q17: When applying the master control command MC N0 M100, how should the N0 M100 contact on the left bus be input?
A: The N0 M100 contact on the left busbar does not need to be manually entered. When the programming software is in write mode, the contact is not present on the left busbar. Simply switch the mode to read mode or monitor mode to make the contact appear automatically.
Q18: Why can't the programming software on my computer communicate with the Maexin PLC? How should I configure the communication cable port?
A: There are several reasons why communication might fail: 1. The PLC might not be powered on; 2. The project type created by the programming software might be different from the actual PLC type; 3. There might be a problem with the communication port settings; 4. A USB to RS232 cable might be used, but the driver might not be installed or might not be installed correctly. There are many possible reasons, and you need to check them one by one. There are two main types of programming cables: SC-09 and USB-SC-09. When using the SC-09, if your computer does not have an RS232 interface, you need to configure a USB/RS232 converter. When purchasing this converter, you also need to install the driver. After installing the driver, the virtual RS232 port number of the converter, such as COM4, will appear in the computer's Device Manager. You need to select this port number when downloading and uploading during programming.
Q19: How should I input the contact comparison instruction [<= D10 K100]? Why can't I input it?
A: To input the contact comparison instruction, you can directly type LD<= D10 K100 on the keyboard. Note that there is no space between LD and the <= sign, but there is a space between the <= sign and D10, and between D10 and K100. Also note that if the contact comparison instruction is a 32-bit instruction [D<= D10 K100], then you directly type LDD<= D10 K100 on the keyboard. Note that it is LD followed by D, not DMOV or other function instructions which are preceded by D.
Q20: What are K2M0 and K2Y0 in the instruction [MOV K2M0 K2Y0], and what does this instruction mean?
A: K2M0 and K2Y0 are combination bit elements. K2 represents the number of groups of combination bit elements, with K2 representing two groups. Each group is a four-bit element, so two groups are 8 bits. Therefore, K2M0 represents the eight bits M0-M7, and K2Y0 represents the eight bits Y0-Y7. The instruction [MOV K2M0 K2Y0] transfers the binary data from K2M0 to K2Y0. In fact, it controls the output state of Y0-Y7 through the binary bits of M0-M7.
Q21: Why is the ERR light on my Maison PLC always red?
A: A red LC ERR light indicates a fault, which could be a hardware or software malfunction. You can connect the PLC to the programming software and then use the "PLC Diagnostics" option in the software menu to determine the specific fault.
Q22: What load can the transistor output of a Maxim PLC drive? Can it be directly connected to a relay? Does it need a protection device? Can it directly drive a solid-state relay?
A: The maximum load capacity of a PLC with crystal output is about 0.5A. Solid-state relays can be driven by themselves. It depends on the type of relay. If it is a 24V intermediate relay, it can be driven.
Q23: Why is it said that PLC systems have high reliability and strong anti-interference capabilities?
A: In terms of PLC hardware design, to improve anti-interference performance, optocouplers are used for both digital inputs and outputs, and electrical isolation is achieved between the internal and external circuits of the PLC, effectively eliminating the impact of external electromagnetic interference on the PLC's internal circuitry. Furthermore, multiple filtering circuits, such as LC filters, RC filters, and digital filters, are designed into the PLC's power supply lines and I/O loops to reduce the impact of high-frequency interference. These hardware design features give the PLC strong anti-interference capabilities and high reliability.
Q24: What is the result of the octal number 35 + 47 in octal? What is it in decimal?
A: The result of 35 + 47 in octal is 104 in octal and 82 in decimal. Octal numbers only range from 0 to 7, and carry over to the next decimal number when they reach 8. That is to say, 10 in octal is 8 in decimal, 11 in octal is 9 in decimal, and so on.
Q25: Can the MX1S-20MT be expanded with modules? How are the input/output port numbers defined for expansion modules? For example, is X13 followed by X14?
A: Maixin MX1S series PLCs only have basic units; there are no expansion units or modules for extended I/O. The input/output port numbers after the expansion modules should be used sequentially and cannot skip numbers. X13 is followed by X20, not X14.
Q26: How do you understand 16-bit and 32-bit operations?
A: Data registers participate in operations with 16 bits. Because each data register of Maxim is 16 bits, if you want to perform 32-bit operations, you must have two adjacent data registers, such as B0 and B1, to form a 32-bit operation. It is also stipulated that B0 is the lower 16 bits, the low bits, and B1 is the higher 16 bits, the high bits. Its sign bit is in the highest position of the high bits. Bit B31 is called the sign bit. The 16 bits are in the highest bit of the 16-bit register, that is, B15 is the sign bit. 16-bit operations are 16-bit addition, subtraction, multiplication, and division, and 32-bit operations are 32-bit operations.
Q27: How do I use the END instruction for segmented debugging when debugging a program?
A: The END instruction in PLC is the end instruction. When debugging a program, you can insert the END instruction after each program segment and debug segment by segment starting from the first segment. After debugging, you must delete the END instruction in the middle of the program. This method is also very useful for debugging the program.
Q28: Are the SET and RST instructions function instructions?
A: SET and RST are basic logic control instructions, not function instructions. Basic logic instructions are mainly used for processing switch signals, while function instructions can be used for data processing, including data transmission, transformation, calculation, and program flow control. In addition, function instructions can also be used to handle data transmission and control between the PLC and external devices.
Q29: Why did "Start" appear at all XO contact positions on the ladder diagram after I annotated the XO contact with "Start"? Is it possible to annotate different positions on the XO?
A: You cannot make different annotations at different positions of XO. If "Start" is annotated at the XO contact, then the corresponding annotation for X0 is "Start". Once defined, it is equivalent to a unique annotation, so "Start" appears at all XO contact positions.
Q30: Can the comparison instruction (LD=) in Maixin PLC compare floating-point numbers?
A: No, there are specific instructions for floating-point comparison.
Q31: Can the D register of a Maixin PLC store the letters NBAG?
A: Yes, it can be stored in ASCII code.
Q32: When editing a PLC program (write mode), if I try to modify the original program, a new line keeps automatically appearing, making it impossible to edit within the original program. I have to delete the original program and rewrite it. To illustrate, if the normally open contact of X0 outputs Y0, and I click Y0, a modification menu pops up, I change it to Y1, and then click OK, it automatically outputs Y0 in parallel on the next line. The same thing happens with other function instructions; this is very cumbersome. What settings are causing this?
A: It's because "Insert mode" was used. If you've used it, just press the "Insert" key on your keyboard again to revert to the previous mode.
Q33: What if I forget my login keyword?
A: If there is a backup program, you can first clear the PLC memory and then rewrite the parameters and program.
Q34: What is the difference between file registers and general-purpose registers?
A: File registers are convenient for storing pre-determined values (such as product inspection specifications). Ordinary registers, except for their holding areas, have all their contents cleared when the PLC is powered off. Therefore, they are generally used as temporary storage areas.
Q35: Why does the solenoid valve burn out repeatedly after being connected to the PLC?
A: When a solenoid valve is connected to an inductive load, it will generate a self-induced electromotive force when it is turned off. This electromotive force will accumulate on the contacts. If the voltage across the contacts is too high, it will break down. If it is a DC solenoid valve, a freewheeling diode can be added. If it is an AC solenoid valve, a surge protector can be added.
Q36: How is the soft component (auxiliary relay state) that maintains its state during a power outage used in general applications?
A: When the PLC is running, use the initialization pulse to clear the necessary areas via the ZRST command. If you need to clear the power outage holding areas, please use M8032.
Q37: Do I need batteries when using the memory cartridge?
A: Memory modules other than RAM do not require batteries. However, batteries are needed when using clock functions, auxiliary relays, data registers, and other holding devices. Additionally, batteries are required when using special data registers and special auxiliary relays. Please refer to the programming manual for details.
Q38: During PLC operation, the power LED either goes out or flashes.
A: Disconnect the wiring at the (power supply) terminal to confirm if normal operation is restored. If normal operation is restored, it may be due to a short circuit in the load or excessive load current causing the power supply capacity to overload and trigger the protection function. If normal operation is not restored, please contact Maixin Motor's after-sales service department.
Q39: What is the register corresponding to the analog potentiometer that comes with the MX1S?
A: The MX1S programmable controller has two built-in potentiometers: VR1: D8030 and VR2: D8031.
Q40: When performing floating-point calculations, if the binary floating-point number is converted to a decimal floating-point number, the value seen in monitoring mode is different from the theoretical value calculated.
A: MX PLC CPU floating-point operations are single-precision, which has slight deviations. The results will vary depending on the CPU used.
Q41: Will the program be lost when the PLC battery is replaced?
A: If a new battery is inserted into the socket within 20 seconds of being unplugged, the program will not be lost. However, if the battery LED is left unused for an extended period after being switched on, the voltage of the battery before replacement may be lower than the specified value. In this case, the program will be lost when the PLC power is cut off.
Q42: Can the MX series programmable controller maintain the output state during RUN when it is in STOP mode?
A: When the MX series programmable controller drives the special auxiliary relay M8033, the output state during the RUN phase can be maintained after the programmable controller changes from RUN to STOP.
Q43: What are index registers (V, Z)?
A: Index registers are special registers that, in addition to being used in the same way as data registers, can also be used in conjunction with other device numbers and values in application instructions to change the device number and value within the program. Among the registers, there are two types called index (modifier) registers: V and Z. V and Z are attached to other devices as shown below: [When V0, Z0=5] D100V0=D105, C20Z0=C25 ← Device number V□ or Z□ value. Data registers and index registers can be used to indirectly specify the set values of timers and counters, and are also used in application instructions.
Q44: What are the consequences when the battery voltage of the MX3U series programmable controller drops?
A : When the battery voltage drops due to factors such as battery life, it cannot properly maintain the program (when the memory cartridge is not used) and the state of soft components and clock during power outages.
Q45: Can the MX3U series programmable controllers use power failure holding soft devices as non-power failure holding soft devices?
A: The MX3U series programmable controller allows some power-failure holding soft elements to be changed to non-power-failure holding soft elements, depending on the parameter settings. However, soft elements specifically designed for power-failure holding cannot be changed to non-power-failure holding soft elements. In this case, the holding soft element is cleared using the initialization pulse (M8002) in the program, allowing it to be used as a non-power-failure holding soft element.
Q46: What are the effective number of bits and the processing range of a binary floating-point number?
A: Significant digits: The significant digits of a binary floating-point number, when represented in decimal, are approximately 7 digits. The processing range of binary floating-point numbers is shown below.
- Minimum absolute value: 1175494 × 10⁻⁴⁴
- Maximum absolute value: 3402823 × 10³²
Q47: What is the range specified for a decimal constant?
A: [K] is the symbol for a decimal integer, mainly used to specify the set value of timers and counters, or the value in the operand of application instructions. (For example: K1234) The range of decimal constants is as follows: - When using word data (16 bits): K-32768～K32767
- When using 2 words of data (32 bits): K-2,147,483,648 to K2,147,483,647
Q48: Can a real number be specified directly on the MX3U?
A: In the MX3U series programmable controllers, [E] is the symbol for real numbers (floating-point data), mainly used to specify the operand values of application instructions. (For example: E1.234 or E1.234 3) The specified range for real numbers is -1.0×2¹²⁸ to -1.0×2⁻¹²⁶, 0, and 1.0×2⁻¹²⁶ to 1.0×2¹²⁸. In sequential control programs, real numbers can be specified in two ways: "normal representation" and "exponential representation".
- The normal representation specifies the value to be set. For example, 10.2345 is specified as E10.2345.
- The exponent indicates that the set value is specified as (value) × 10^n. For example, 1234 is specified as E1.234 3. The [3] in [E1.234 3] represents 10 to the power of n (3 is 10^3).
Q49: Can the bits of a word element be directly specified and used as bit data?
A: The bits of the specified word soft element in the MX3U series programmable controller can be used as bit data. When specifying the bits of a word soft element, please use the word soft element number and bit number (hexadecimal) for setting. (For example: D0.0 represents bit number 0 of data register D0.) Indexing cannot be performed on the soft element number or bit number. Target word soft element: Data register or special data register. Bit number: 0～F (hexadecimal). For example: LD D0.F OUT D0.3
Q50: Can the soft elements used by the LD and LDI instructions be modified using index registers (V, Z)?
A: In the MX3U series programmable controller, the soft elements used in the LD and LDI instructions can be modified using index registers (V, Z). (Status (S), special auxiliary relays (M), 32-bit counters (C), and D□.b cannot be modified).
Q51: In the soft device used by the LD and LDI instructions, can the bit of the data register (D) be specified?
A: In the MX3U series programmable controllers, the bits of the data register (D) can be directly specified in the soft devices used by the LD and LDI instructions. When executing bit-specific data register instructions, enter "." after the data register (D) number, followed by the bit number (0~F). Only 16 bits of the data register are valid. Please specify the bit numbers starting from the least significant bit in the order 0, 1, 2, ..., 9, A, B, ..., F. For example: LD D0.3 OUT Y0. The third bit of D0 determines whether the LD contact is ON (conducting) or OFF (not conducting).
Q52: Question about connecting NPN and PNP input terminals of the Maxim MX series PLC. The Maxim MX series PLC input is active low, meaning NPN photoelectric switches can be used. However, for PNP photoelectric switches (three-wire system), connecting a 470Ω resistor in series with the signal (black wire) and then reversing the logic in the program will also allow them to work.
A: PNP requires an external power supply. The MX series are all sink type, so an external NPN works fine. PNP is source type output, so it will not work if directly connected.
Q53: How can I implement automatic cycling in a Maixin PLC? Specifically, I wrote a program that picks up items from one side, places them on a conveyor belt, and stops the conveyor at a certain point. Then, the pusher motor starts, retracting the items into a basket below. The problem is that I have to press a switch to give it a pick-up command each time for it to pick up items automatically. Changing it to a normally closed switch prevents it from doing so. What instruction can I use to make it pick up items automatically, i.e., to cycle through the system?
A: The command to trigger the switch first activates M0.0, and then M0.0 activates the steps to grab the object. To achieve the automatic loop function, after the object retracts, triggering M0.0 again is equivalent to manually pressing the switch again, which will then allow you to grab the object again.
Q54: What does [DDIV D136 D140 D128] mean in the Maixin PLC program?
A: DDIV (32-bit division instruction).
D137, D136 (place the dividend).
D141, D140 (place divisors).
D129, D128 (Fang Shang).
Q55: What do rising edge contact and falling edge contact mean in Maixin PLC programming software?
A: Rising edge and falling edge contact instructions in Maixin PLC programming software. The PLS rising edge differential pulse output instruction differentiates the rising edge of the specified signal and outputs a pulse signal with a pulse width of one scan cycle. The PLF falling edge differential pulse output instruction differentiates the falling edge of the specified signal and outputs a pulse signal with a pulse width of one scan cycle. PLS and PLF are only effective when the input signal changes.
Q56: What does [= D0 K0] mean in Maixin PLC? What does MOV K0 DO mean?
A: LD M8000 [= D0 K0] OUT Y0 means that when M8000 is turned on and the data in D0 is equal to 0, Y0 is engaged. LD M8000 [＞D0 K0] OUT Y0 means that when M8000 is turned on and the data in D0 is greater than 0, Y0 is engaged. LD M8000 MOV K0 D0 means that when M8000 is turned on, the data 0 is transferred to DO.
Q57: What does it mean when the highest bit of a Maixin PLC register is the sign bit?
A: The sign bit in the register is used to indicate whether the data stored in the memory is positive or negative. If the sign bit is 1, the value is negative, and if it is 0, the value is positive.
Q58: What does T10 D8030 mean in Maixin PLC?
A: This means that the timing of T10 is adjusted by the built-in potentiometer VR1 D8030 (an integer from 0 to 255), so the maximum is 25.5 seconds.
Q59: How do I import the ladder diagram from the Maixin PLC programming software into Word?
A : You can use a printer to print the program. Install a PDF printer, and you can print the program into a document, then insert those documents into a Word document.
Q60: How to control the forward and reverse rotation of a DC motor in a Maixin PLC program?
A: Use a digital-to-analog converter to output a 0-5V signal. Then, find an external dedicated DC speed controller with a 0-5V input signal. The output voltage will provide positive feedback based on the different output voltages, corresponding to the voltage levels from low to high. The minimum is 0V, and the maximum is your motor's normal operating voltage. For detailed parameters, please refer to the specifications of the DC speed controller.
Q61: What does INCP mean in Maixin PLC?
A: INCP simply increments the register by 1, adding a condition beforehand. For example, INCP D100 only counts as one operation even if the data inside D100 is 1 and the register is continuously connected.
Q62: Mysen PLC M500 and above are power-off retention type. How to set it to non-power-off retention type?
A: 1. Click the display menu and select Project Data List. 2. Click Parameters on the left and select PLC Parameters. 3. In the MX Parameter Settings dialog box, select Soft Components. 4. Change the latch start item in the Auxiliary Relay section.
Special Note: The material in this article comes from the internet, and the copyright belongs to the original author.
