Abstract: DC high-voltage power supplies are used to accelerate, deflect, and extract ion beams in ion beam transmission. This paper introduces the remote control of a 10kV high-voltage DC power supply based on the Advantech ADAM-4000 series distributed module. Its control functions include remote switching operations, real-time acquisition of power supply operating status, and output high-voltage regulation. Keywords: Remote control; Distributed module; High voltage 1 Introduction DC high-voltage power supplies are used to accelerate, deflect, and extract ion beams in ion beam transmission. In practical operation, the output high-voltage value needs frequent adjustment. Using potentiometers often fails to meet the required output voltage regulation accuracy and is not easy to precisely adjust the output high-voltage value. Due to the importance of high-voltage power supplies in ion beam transmission, remote control of high-voltage power supplies is crucial. The Advantech ADAM-4000 series distributed module adopts the RS-485 bus standard and has various functional modules, including digital input/output, digital-to-analog conversion, analog-to-digital conversion, and communication modules. By designing additional circuits based on the functions of the corresponding modules, we achieved remote control of a 10kV high-voltage power supply. The main control computer enables remote power-on, power-off, and fault reset operations for the DC high-voltage power supply, real-time acquisition of the power supply's operating status, and remote control functions such as adjusting the output high voltage. 2. RS-485 Bus Overview RS-485 is a bus-type communication network that supports half-duplex and full-duplex communication modes. RS-485 transmits signals in a differential balanced manner, fundamentally eliminating the signal ground wire, possessing strong common-mode interference immunity, allowing one transmitter to drive multiple load devices on a single twisted pair, and offering low transmission line cost. A typical RS-485 half-duplex communication network is shown in Figure 1. In an RS-485 network, each station has a fixed address. Only one station can establish data communication with the host computer at any given time, sending and receiving data, while other stations can only be in receiving mode to avoid data collision errors. A maximum of 32 control nodes are allowed to connect to a standard RS-485 bus. [align=center]Figure 1. Typical RS-485 half-duplex communication network[/align] In the current field of automation, RS-485 control networks are widely used due to their simple interface, long signal transmission distance (up to 4000 feet), high transmission rate (maximum 10M), and high reliability. Simultaneously, due to the rapid development of network technology, field device control networks composed of RS-485 buses can be connected to Ethernet via gateways and other technologies to achieve networked control. 3. Functional Overview The main control computer uses digital input/output modules and corresponding internal drive circuits of the power supply to remotely operate the high-voltage power supply and collect real-time data on its operating status; it adjusts the output voltage of the high-voltage power supply through the digital-to-analog converter module; and it obtains the output high voltage and current values ​​of the power supply through analog-to-digital conversion. The ADAM-4000 series digital input/output modules, digital-to-analog converter modules, and analog-to-digital converter modules use the RS-485 standard bus, and each functional module can be set with an address. The RS-485 network uses a master-slave mode, with the main control computer acting as a master node and the remaining functional modules as slave nodes. After the control system is assembled, the main control computer accesses the addresses of each functional module and sends control command strings to achieve the corresponding control functions. An RS-232/RS-485 converter is used to convert the RS-232 level signal of the main control computer into an RS-485 bus standard signal, thereby enabling control of each functional module. The control principle of the high-voltage power supply is shown in Figure 2. The modules used in the high-voltage power supply remote control system are described below: Digital Input/Output Module ADAM4050: This module has 7 digital input channels and 8 digital output channels. Its digital input signals are TTL level or relay nodes, and the digital output is an open-collector output, capable of driving miniature relays. Through the internal control interface of the high-voltage power supply, the power-on/off operation and operating status acquisition are realized. Analog Output Module ADAM4024: This module can output 4 analog signals with a resolution of 12 bits. It has current output and voltage output modes. The output range in voltage output mode is ±10V, and its output ramp can be adjusted through programming. One analog output of this module serves as the voltage reference for remote control and regulation of the high-voltage power supply output. The analog input module ADAM4017 has 6 differential signal input channels and 2 single-ended signal input channels, with current and voltage signal input modes. The voltage signal input range is ±1V, ±5V, and ±10V. Its two differential signal input terminals respectively acquire the output voltage value of the high-voltage power supply and the load current value. The isolated RS-232/RS-485 converter ADAM4520 converts RS-232 level signals to RS-485 bus signals, with an isolation voltage of 3000VDC. The main control computer communicates with each functional module via the RS-485 bus protocol. The control software for the high-voltage power supply is developed using the Visual Basic 6.0 integrated development environment. Its control functions include: power-on, power-off, and fault reset of the high-voltage power supply; real-time acquisition of power supply operating status; adjustment of output voltage value and real-time measurement of output voltage value; and communication port detection. By designing a special timer in the control software, the main control computer can acquire the power supply's operating status and output high voltage value in real time. [align=center] Figure 2. Control principle diagram of the high voltage power supply[/align] 4 Communication Software Design The control software of the main control computer mainly includes a communication module, a control function module, and a data display and processing module. The control function module enables remote power-on, power-off, fault reset, output voltage adjustment, and power supply operating status display of the high voltage power supply. Data communication with each function module is achieved through the communication control software. When the computer sends data to the high voltage power supply, the corresponding function module installed inside the power supply returns the corresponding instruction and displays the execution result on the operation interface. Each control instruction contains an address and control data that are transmitted to the corresponding control module as a string. Each module operates accordingly based on the module address and instruction sent by the main control computer. VB6.0 provides many controls for users to choose from, among which MSComm32.OCX is a control for serial communication. The MSComm communication control has rich properties and events for serial communication, and can create full-duplex, event-driven, efficient, and practical communication programs. Microsoft Communications Control (MSComm) is an ActiveX control provided by Microsoft to simplify serial communication programming under Windows. It offers applications a convenient way to send and receive data via a serial interface. It can be used to create full-duplex, event-driven, efficient, and practical communication programs. Specifically, it provides two methods for handling communication: event-driven and polling. The event-driven method is a very effective way to handle serial port interactions. The MSComm control triggers the OnComm event when a specified amount of data is received or sent on the serial port, or when the state changes. The OnComm event can also check and handle communication errors. The advantage of this method is timely program response and high reliability. Each MSComm control corresponds to one serial port. If an application needs to access multiple serial ports, multiple MSComm controls must be used. The polling method is essentially still event-driven, but in some cases, it is more convenient. After each critical function of the program, events and communication errors can be detected by querying the values ​​of certain properties of the MSComm control, such as the CommEvent and InBufferCount properties. If the application is small and self-sustaining, this method may be preferable. Both communication methods can achieve the purpose of sending and receiving data; the choice of method depends on the actual system environment. For high-voltage power supply control communication software, a polling method is used in the design. The function of the communication subroutine is to transmit the command string sent by the master computer to the RS-485 bus. Different control modules receive the command string, and only the module with the same address information contained in the command string will execute the corresponding control function and return the execution result string. The communication software subroutine list is as follows: Private Sub sendadv(Outstring, n) MSComm1.CommPort = Comm_Port 'Select RS232 communication port MSComm1.Settings = "9600,N,8,1" 'Set baud rate, parity bit, data bit, stop bit MSComm1.InputLen = 512 'Set buffer size MSComm1.PortOpen = True 'Open serial port MSComm1.RThreshold = n MSComm1.Output = Outstring + Chr(13) 'Send the string marked with a carriage return Do Until MSComm1.InBufferCount > 0 DoEvents Error_Flag = Error_Flag + 1 If Error_Flag > 1000 Then Error_info = "Failed to send control command!" ok = MsgBox(Error_info, vbOKOnly + vbExclamation) GoTo Return1 End If Loop Instring = MSComm1.Input … … Return1: MSComm1.PortOpen = False End Sub 5 Module Initialization The ADAM-4000 series modules all have corresponding instruction sets to enable the control software to implement corresponding control functions. The instruction words of each module are in the form of ASCII characters. The control software sends the instructions to the corresponding modules in the specified instruction format to achieve the corresponding control functions. In the control software, each functional module is initialized first, including setting parameters such as the address, baud rate, input/output mode, and module type of each module. The instruction for setting the module is sent out in the form of a string, ending with a newline character. When the control software starts, each module is initialized as follows: … … Outstring = "%0101400600" 'Set the address of 4050 to 01H, I/O module, baud rate 9600. n = Len(Outstring) Call sendadv(Outstring, n) 'Call the communication subroutine Outstring = "%0202000603" 'Set the address of 4024 to 02H, the baud rate to 9600, and the output analog quantity rise slope. n = Len(Outstring) Call sendadv(Outstring, n) Outstring = "$027C0R32" 'Set the voltage output range of channel 0 of 4024 to -10V to +10V. n = Len(Outstring) Call sendadv(Outstring, n) Outstring = "%0303080600" 'Set the address of 4017 to 03H, the analog quantity input range to ±10V, and the baud rate to 9600. n = Len(Outstring) Call sendadv(Outstring, n) … … 6 Conclusion The remote control system of the DC high-voltage power supply based on distributed modules has high-resolution digital-to-analog converters and analog-to-digital converters, which meet the requirements for the output regulation accuracy of the high-voltage power supply. The system boasts strong flexibility and expandability due to its RS485 bus control method; its safety and reliability are enhanced by the use of isolated communication control. The implementation of remote control of the high-voltage power supply reduces the need for personnel to directly adjust the output at the experimental site, allowing them to monitor the power supply's operating status and output voltage via the main control computer. After repeated debugging and reliability testing, the requirements for remote power supply control have been met. The author's innovation lies in utilizing distributed modules to achieve high-precision remote control of the high-voltage DC power supply, ensuring the operational safety of physics experiment personnel and possessing significant potential for widespread application in engineering practice. References: [1] Fan Yizhi, Chen Liyuan. Visual Basic and RS-232 Serial Communication Control [M]. Beijing: Tsinghua University Press, 2002. 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