Developement of Multi Interface Board for Educational Trainer Kit

Transcription

1 Journal of Engineering Technology Vol. 2(1): 1-5, 2012 ISSN UniKLBMI Developement of Multi Interface Board for Educational Trainer Kit M.R. Abdullah, Z. Zaharudin, Z. Mahmoodin, Z. Zainuddin & A. Syahril Universiti Kuala Lumpur-British Malaysian Institute Gombak, Selangor, Malaysia Corresponding Abstract: Nowadays the computer is widely used not only for documentation purpose but also as multi platform equipment for various tasks such as measurement, controls and data acquisition. A Multi Interface Board (MIB) is designed as an educational trainer kit. It support computer interfacing programming for parallel, serial and universal serial bus (USB) with interactive input/output facilities. The MIB platform consists of several interfaces section that suits with a multi protocol using single application board for: 1-Displays such as LCD, Dot Matrix, 7 segments and LEDs. 2- Motors such as DC, Servo and Stepper. 3-Digital inputs such as keypad and switches. 4-Analog inputs such as light, temperature and voltage. The final product is expected to be economical and fully satisfy the user requirement in learning and applying the real time PC based programming. Keywords: Computer, data acquisition, interface board, USB, PC based programming 1.0 INTRODUCTION In the developed world almost everybody interacts with personal computers (PC). It has been used for learning, entertainment, information and as tools to leverage our knowledge and intelligence [1]. A PC based interfacing for real time control applications had shown a high demand with the advancement in computer system [2]. Since from that day, the PC based computer system had evolve from parallel line printer port to RS232 serial and USB data communication [3]. The parallel port is packaged into data or centronic connector that is represented by 25 wires consists of status, data and control port [4]. A parallel port data transfer rated at 8 Mbps lead to its popularity by sending the data byte simultaneously [5]. A serial communication with RS232 protocol was proved to be economical than the parallel port on a long distance communication. Only 3 wires such as transmitter, receiver and signal ground was consumed either as simplex, half duplex or full duplex [6]. The emergence of USB taking the full advantages of serial and parallel protocol. An economic and enhancement factors such as speed and simplicity cause USB port was embedded in a modern PC [7]. Table 1 PC s protocol comparison Interface Format Distance Speed Typical use (bps) printer port Parallel M Printers, drivers RS232 serial K Modern,mou se, USB serial 16 (Up to 96 ft. with 5 hubs) 1.5M, 12M and 480M Mouse, Keyboard, drive, audio and printer A comparison of the PC protocols could be referred in the Table 1. A PC based control had been adapted for a data acquisition and controlling purposes [8]. A smart, adaptive and intelligent system was implemented efficiently on the assistance of PC based applications [9]. 2.0 MATERIALS AND METHODS In general, the MIB is carried with the I/O interconnections as visualized in Fig. 1. A MIB system is based on a discrete components that mimic to a conventional microprocessor system with address, control and data buses. Integrated chips such as demultiplexer, 1

2 Journal of Engineering Technology Vol.2 (1): 1-5, 2012 latches and buffers are used to support MIB as a versatile trainer board. potentiometer for the measurements of intensity, temperature and voltage. A voltage divider is used with the potentiometer and LDR to support voltage and intensity measurement. An analog temperature sensor that generating 10 mv per degree centigrade is used for a basic application of measurement and instrumentation. A single supply operational amplifier LM324 is used to satisfy an analog to digital conversion (ADC) resolution at mv and LM35DZ range from 0 C/ 10 mv~ 100 C/ 1V. It was config.d as a non-inverting amplifier with voltage gain of 5 to optimize the ADC performance in the temperature measurement. These analog inputs are multiplex on a single data bus to an ADC0804. Upon software decoding, only a selected sensor measurement will be interfaced to the ADC0804 for 8-bit analog to digital conversion. Then, the ADC0804 data is fed to a 74LS157, a nibble multiplexer for transferring data to the PC status port. Fig. 3 (a) 16 2 LCD Module (b) 7 Segments and Dot Matrix Module Fig. 1 Block Diagram of Multiple Interface Board As shown in Fig. 3, the MIB display outputs consists of Liquid Crystal Displays (LCD), 7 segments module, Dot Matrix and Light Emitting Diode (LEDs). A 16 Character x 2 Line LCD with HD44780 chipset is used in a byte mode mode data transfer. The LCD enable (E) and register select (RS) pin are connected to the control port for selecting the LCD command and data register. A character and numeric are displayed on the LCD according to the LCD CGRAM table that pointed by key ASCII event function in visual basic. Six digits common anode seven segments are available to allow various experiment such as digital clock, counter and display board. BCD decoders and latches are the components for supporting 7-segments numbers with minimal connection. For setting the 7segments BCD numbers, each of 74HC373 latch clock are connected to the PC control port. A 5 x 7 common anode dot matrix LED Display are used on MIB. Four dot matrix modules are available to deliver concept and provide exercise on an interactive running display. The dot matrix character are formed by the row and column scanning. Seven NPN Transistors are used for a row scanning and shift registers, inverters with darlington drivers for column scanning. A look table algorithm is applied for programming the dot matrix module. In this work, visual basic 6.0 software with number of active-x objects are used to evaluate the MIB functionality. The Graphical User Interface (GUI) was designed to embed a command for selecting the MIB respective devices. The MIB consists of three interface sections such as digital input, analog input and digital output. In Fig. 2, 4 4 Keypad and 8 switches are dedicated for the digital input. Fig. 2 (a) Keypad Module (b) 8 bit-slide Switch A 74C922 keypad encoder was used to encode up to four bit data in a matrix array. A 8 switches was designed as an active low mode to provide basic input programming applications. The analog inputs consist of sensors such as Light Dependent Resistor (LDR), LM35Dz, and 2

3 Journal of Engineering Technology Vol.2 (1): 1-5, 2012 Typical motors shown in Fig. 4 such as stepper, servo and DC motor are offered on the MIB trainer. A L293D is a driver used for controlling DC motor to move forward and reverse direction. A stepper motor controller is optimized with a ULN2803 darlington driver to sink current up to 500 ma. This support stepper motor operations on single, half and full stepping mode. For the servo motor, 0 ms to 2.5 ms pulse width was generated from the PC data port to control 0~180 degrees angular motion Fig. 4 (a) DC motor controller (b) Bipolar and servo motor controller Ain ADCout 2 Vref 2 n (2) As indicated in equation 3, ADC per step change is mvwhen Vref was config.d to 2.5 V. (3) Vref 2 ADCstep 2 n As a result when Vref is reduced this will enhancing the ADC sensitivity. The temperature measurement was virtually displayed on an angular gauge and calibrated as stated in equation 4. ADCout 1 Temp ADCstep (4) As illustrated in Fig. 6, an intensity measurement circuit was designed to support MIB analog input. The circuit connection cause the voltage proportional to the intensity. In Fig. 5, a computer aided design software such as EAGLE (Easily Applicable Graphical Layout Editor) was used to draw an electronic schematic and produce an autorouted layout of printed circuit board (PCB). Fig. 6 Light Intensity measurement circuit Thus, when Light Dependant Resistor (LDR) increases in a dark the Vout also increases as tabulated in Table 2. Fig. 5 Complete fabricated PCB board circuit 3.0 RESULTS AND DISCUSSION As a result in this study, low cost, small size, portable and compact MIB trainer was designed with an interactive applications in a visual basic software. The MIB focus to the development parts as discussed below:- 3.1 Hardware Development Table 2 LDR table of conversion Intensity LDR(Ω) R1 (Ω) Vout (V) Dark 1.5 MΩ 2 MΩ 2.08 V Bright 10 KΩ 2 MΩ 0.02 V The use of LM35dZ offers a linear temperature measurement as based in the equation 1 below:- y 0.1x 0 (1) Referring equation 1, given x= 100 C then y= 1 V. In equation 2, given Ain =5, Vref=2.5, n= 8 thus ADC out=256. 3

4 Journal of Engineering Technology Vol.2 (1): 1-5, 2012 In Fig. 7, MIB functional test was carried out on a display section for the LCD, Seven Segments and Dot Matrix. Fig. 9 The MIB software driver Fig. 7 Completed MIB board An interactive software modules as in Fig 9 was written for running the MIB hardware modules. These modules are invoked upon user selection via option buttons such as indicated in Fig. 11. A bipolar stepper motor as designed in Fig. 8 is programmed for single, half and full step. The stepper motor will rotate at 1.8º per step and will consume 200 step for 360º. Fig MIB software for Input/ Output module 4.0 CONCLUSION Fig. 8 Stepper motor circuit diagram The MIB trainer system enables students to enhance their programming skills on the devices software driver development. A Personal computer (PC) based interface board with various input output on a single board facilitate students to obtain hardware and software development concept via a PC based control. A native microprocessor system design was referred for designing the MIB trainer system. This include the uses of buffers and latches for multiplexing the address, control and data buses. In order to support the abundant of MIB s I/O, high current voltage regulator rated at 5V, 5A is vital to withstand the MIB s overflow current. A visual basic software was used with numbers of active-x objects to create an interactive software drivers. The MIB trainer system compact with I/O is sought as a first local based trainer designed for a multiplatform PC based interfacing programming. Further research development to assure MIB flexibility to microcontroller, serial and Universal Serial Bus (USB) interfaces will be currently held. 3.2 Software Development Fig. 9 shows an interactive software development for testing each of the hardware modules on the MIB trainer. The selection of option buttons on any input and output modules will cause MIB to decode the data, address and control buses accordingly. MIB consist of temperature measurement, 4x4 keypad control, digital clock, status readout, voltage measurement, LDR interfaces, control port tester, byte readout and motor control 4

5 Journal of Engineering Technology Vol.2 (1): 1-5, 2012 REFERENCES [1]. Trevor I. Williams, A Short History of Twentieth-Century Technology c c. 1950, Clarendon Press, [2]. Parallel Port Complete Programming, Interfacing & Using the PC s Parallel Printer Port, Jan Axelson, Lakeview Research, Madison, WI [3]. PC Ph.D. Inside PC Interfacing,Myke Predko, McGraw- Hill, ISBN [4]. Programming The Parallel Port Interfacing The PC For Data Acquisition and Process Control Dhananjay V.Gadre, Publishers Group West, ISBN [5]. Controlling The World with Your PC, Paul Bergsman, LLH Technology Publishing, ISBN [6]. Serial Port Complete Programming& Circuits for RS-232 and RS-485 Links and Networks, Jan Axelson, Lakeview Research, Madison, WI