Key word: RS-485 Fuel cell PIC16F873 Monolithic voltage
1 introduction
The fuel cell is one of the 21st century most hopeful substitution present automobile fuel oil internal combustion engine’s new power systems, it is one kind transforms directly H2 and the O2 chemical energy through the electrode reaction the electrical energy the installment. A fuel voltaic pile is connects many piece of battery pieces the constitution, the entire voltaic pile’s performance and the monolithic battery voltage has the very big relations. Therefore has under the essential gathering dissimilar condition in fuel cell’s development the monolithic battery’s voltage value, discovers H2 and between the O2 response environment and the monolithic battery voltage relations through the analysis. What this article needs to introduce is the author unit in the 25kW fuel cell passenger vehicle project which carries on, the fuel cell monolithic voltage inspects the test, the analysis system’s design. This system’s superior machine software uses the VB6.0 programming language to carry on the development, this language function is formidable, has object-oriented and the visualization programming, the contact surface is friendly, is suitable for specially under the Windows environment the graphical interface and the user program establishment, the data acquisition completes by many take 8 PIC monolithic integrated circuits as the core data acquisition module.
2 system compositions and principle of work
This system by the superior machine, the master control monolithic integrated circuit and certain data acquisition module is composed, as shown in Figure 1. The superior machine is an industrial control computer, its major function is realizes through the RS-232 serial port with the master control monolithic integrated circuit’s correspondence, the receive gathering data and the transmission control command; Real time display monolithic battery’s voltage value and plan identical frequently monolithic voltage change trend curve; The metrical data classification will preserve the database, and has to the measurement result carries on many kinds of mathematical analyses the function.
Master control monolithic receive from superior machine control command
Figure 1 System constitutional diagram
Realizes to each data module control, and the data which sends in each module through the RS-232 serial port repeater gives the superior machine. The master control monolithic integrated circuit and each data acquisition module uses the RS-485 main line to carry on the correspondence, and supposes Cheng Zhucong the structure, the master control monolithic integrated circuit supposes for the main engine, each data acquisition module for from machine. The master control monolithic integrated circuit after receiving the superior machine examination starts the order, according to the wheel follows the way in turn to give each data acquisition module to send the gathering order, after issues a gathering order every time waited for that receives this gathering module the gathering data, if in the standby period adduction to the gathering module sending back’s gathering data, gives the data pack repeater the superior machine; If the waiting overtime had still not received the data directly to send the gathering order to the next gathering module, continue the recycle like this.
Various data acquisition module’s software and hardware constitution is completely same, and realizes through the RS-485 main line with the master control monolithic integrated circuit’s correspondence. Each data acquisition module in receives starts 16 piece of battery voltage value which after the master control monolithic integrated circuit’s test order is responsible for it to test to carry on the sampling, then transmits together the sampling obtained 16 piece of battery voltage value pack for the master control monolithic integrated circuit. Each data acquisition module can gather 16 piece of monolithic battery’s voltages, may fluctuate the data acquisition module correspondingly according to the battery piece total quantity.
3 data acquisition module design
In this inspects in the system monolithic battery voltage value gathering is completes by each data module. The data acquisition module is mainly adds some peripheral circuit constitution as shown in Figure take the PIC16F873 monolithic integrated circuit as the core 2. The PIC16F873 monolithic integrated circuit is section of simplification set of instructions (RISC) which Microchip Corporation produces, the Harvard double main line and two level of command system running water line structure high performance-to-price ratio 8 embedded controllers, has the integration rate to be high, the speed is quick, the working voltage is low, the power loss is low, the I/O direct drive, the instruction simple easy to study characteristics and so on Yi Yong. Its built-in 8k×14 Flash memory, 1 10 four input channel A/D switch, with UART. And may online serial program (ICSP), the development and the use is very convenient, needs the periphery expansion component to be few. The multi-channel simulated signal’s input is chooses in the data acquisition module through 16 group analog switch CD4067, the monolithic integrated circuit chooses the concrete that group input through I/O mouth RC1~RC4. Because the monolithic battery voltage is quite generally low in 0.5V~1.2V, this voltage in CD4067 approval scope, therefore has not added the isolating circuit in the CD4067 input port. Because data acquisition module and between the master control monolithic integrated circuit is through 485 main line correspondences, therefore monolithic integrated circuit’s serial port input/output must carries on the level switch after MAX485 be able to receive on 485 main lines. The sampling speed may control by the master control monolithic integrated circuit. Because the length limited lower position machine software design has not mentioned in this.
Figure 2 Data acquisition module schematic diagram
4 superior machine signal procedure design
In application VB6.0 inlays MSComm to control, so long as through the simple establishment and the programming, can realize the serial data transmission and the receive. MSComm controlled to provide has a series of sealed the good standard serial communication the attribute and the method, used it to be possible to establish the application procedure and the serial port connection, completed the serial data the transmission and the receive. Its initialization attribute establishment is as follows:
If MSComm1.PortOpen=True Then
MSComm1.PortOpen=False
End If
MSComm1.CommPort=CommNum `serial port number
‘9600 bauds, non-parity check, 8 bit data, a stop position.
MSComm1.Settings= ” 9600, N,8,1 “
MSComm1.InputLen=0
MSComm1.RThreshold=20 `receive data threshold
MSComm1.SThreshold=0 the `transmission cannot complete lives the event
MSComm1.InputMode=comInputModeBinary
`correspondence for binary pattern
MSComm1.PortOpen=True `opens the serial port
MSComm1.InBufferCount=0 `clear spatial receive buffer
MSComm1.OutBufferCount=0 `clear spatial transmission buffer
The lower position machine to superior machine transmission’s data frame form as shown in Figure 3:
Figure 3 Receive data frame type
Each data is composed of 20 bytes, is in turn: A byte’s frame beginning of tape is FF; A byte data set number; 16 byte data; A byte’s verification and, the verification and is the group number and 16 byte data different or result; Last byte for the frame end mark was FD. in 16 byte’s data each byte expressed that a piece of battery’s voltage value, is a 0~255 integer, divides this number 100 and obtains the voltage actual value, generally monolithic battery voltage in 0.5V~1.2V. Carries on when the serial communication receive data with MSComm may select two methods to realize, one kind inquires the way, another kind is the event triggering way. Chooses what in this system is the event triggering way, when in the receive buffer the data byte count arrives at 20 triggers a receive event. The receive signal procedure is as follows:
Private Sub MSComm1_OnComm()
Dim InputData() As Byte
Dim strSum As Byte
Dim i As Integer
Dim Volvalue (0 To 18) As Single
With MSComm1
Select Case .CommEvent ‘judgment correspondence event
comEvReceive: ’receives 20 bytes data
InputData =. Input `reads the receive buffer
If InputData(0) = 253 And InputData(18) = 237 Then the `judgment receives frame form correct otherwise
For i = 1 To 17 Step 1
Volvalue(i) = InputData(i)
Next I
strSum = InputData(1)
For i = 2 To 17 `computation verification sum
strSum = InputData(i) Xor strSum
Next I `will accept the data check and with the transmission verification and different or
If strSum = “0″ Then `, if the receive data is correct
Volvalue(N) = InputData(i)/100
the `conversion obtains the voltage actual value
…………Data processing
Case Else
MSComm1.InBufferCount = 0 `clear spatial receive buffer
MsgBox “serial port correspondence mistake”
Exit Sub
End Sub
In this must pay attention a spot is when reads the data from the buffer, array InputData() must certainly define the Byte type not to be able to be Integer or Single, because the receive pattern establishes as the binary system. The superior machine transmission’s instruction also is very little simple in this does not have the careful analysis.
5 concluding remark
The fuel cell one kind which favors as the 21st century prospect comparison new, the pure energy, concerns its each technology research to be helpful in impels it to further develop to the practical stage. This article has done some work in the monolithic voltage’s examination and in the analysis system’s design. Although is faces the fuel cell, but may also profit from other similar multi-spot examination and control system’s design.
