Dilshan R Jayakody’s Web Log

Few months back I got an old Heathkit IO-12 Oscilloscope from my friend and at the time of delivery this unit is not under the working conditions. Heathkit IO-12 is Value based laboratory oscilloscope with following technical features, Frequency Response : 3 Hz to 4 MHz ≅ 5 MHz Sensitivity : 0.025V/inch Rise time: 8µS Sweep Range : 10 Hz to 500 kHz When I remove the casing of the oscilloscope I found several damaged components (specially capacitors) and wires. After making the careful observation and testings I decided to rewire the whole oscilloscope with new components except the following, 12BH7 Dual Triode 12AU7 Dual Triode 6AN8 Triode Pentode 6AB4 Triode 1V2 ½ Wave Rectifier 6X4 Full Wave Rectifier 6J6 Dual Triode Main Transformer Front end controls (including switches, potentiometers, connectors and indicator) Most of the inductors Cathode Ray Tube, etc As mentioned in the above list all the Values, transformers and some of the critical components are in good condition. Only t...

Sudoku is one of my favorite games and in this project we developed small computer program to play and solve Sudoku puzzles in Microsoft Windows operating systems. Like all of my other computer programs this project is also hosted in sourceforge.net with open source – free software license (Under the terms and conditions of GNU General Public License Version 3 ). This project is developed using Borland C++ and it had following general features, Sudoku Game Panel with multiple user profiles Support custom board styles Auto-play options for all the predefine and user specified puzzles Minimize to tray option Three game play levels (as easy, intermediate and hard) Easy to add any number of custom puzzles Latest version of Mini Sudoku is available to download at minisudoku.sourceforge.net and at Mini Sudoku Ohloh project page . To modify this project user need to use Borland C++Builder 6, NSIS (Nullsoft Scriptable Installer) and Adobe Photoshop (or any other image editor which is capabl...

In this project we design an Inverter to convert 12V DC power source to 230V AC power. This system consist 3 main stages such as oscillator, switching circuit and step up transformer stage. In oscillator we use 4047 CMOS astable multivibrator to generate nearly 60Hz oscillation. In a given configuration, f = 1/(4.4C 2 (R 1 +R 2 )) f = 1/(4.4×(0.1/10 6 )((3.3+33)×10 3 ))) f = 62.609 Hz In a switching stage we use 2SD400 NPN transistors and IRFZ44 N-channel FETs. For the step-up transformer it is recommended to use 12V-0-12V : 230V – 5A transformer. When constructing the circuit it is highly advisable to apply good heat sinks to both Q1 and Q2. If you are plan to use single heat sink to both Q1 and Q2 it is required to place good insulator between the transistors and the heat sink. During the field test we use 12V - 7Ah sealed lead acid battery (which was commonly used in general UPS) with this system and constructed prototype deliver 238V AC in no-load. To get the c...

Automated Home Security system is PIC16F877 based security system with following core features, Support automatic phone dialing using DTMF tones Support inputs from three optical sensors Control external device(s) Built-in alarm with external audio output Allow total customization to the end-users (such as program phone numbers, setup device control sequence, etc) without changing the source code. Password protected system setup In this design we use PIC16F877 8bit microcontroller as main system controller, NE556 dual timer as an alarm system and 7805 as power regulator. To miniaturize the final product we use some amount of surface mounted parts with this design. Application program(s) of PIC microcontroller is developed using C programming language and release under the terms and conditions of GNU General Public License. In this design we use some special electronic components/modules which include LCD display module, 4x4 keyboard matrix, telephone isolation transforme...

TDA2030 is most popular, high quality - low cost audio power amplifier and successive version of TDA2006. Typically TDA2030 deliver 14W in 24V with 4&#8486 output load and 8W in 8&#8486 output load. Because of it’s wider power bandwidth (10Hz to 140 kHz) and extremely small amount of distortion (0.1% - 0.5%), TDA2030 deliver excellent sound quality with higher performance. In this project we design basic version of TDA2030 mono power amplifier for general use and its design to work with 9V – 24V (500mA) Power Supply Unit. When building the circuit it is recommended to use PCB design and its important to attach suitable heat-sink to the TDA2030. In this design it is not necessary to have electrical isolation between the IC and the heat-sink. To get the complete circuit diagrams and PCB designs (Eagle) please check the google drive .

In this project we design high current, high accuracy single rail variable power supply unit using Micrel’s MIC29152 voltage regulator IC. Thanks to the Micrel’s Super Beta PNP fabrication process this regulator has 80mV to 600mV dropout at the full load. With the given values of R1, R2 and TR1, this unit delivers 1.3V to 20V with maximum of 1.5A current. This power supply unit is ideal for most of the analog electronic experiments, as a simple battery charger, as laboratory power supply, etc. Complete circuit diagram, PCB pattern and Eagle source files of this project are available to download in here . When building the circuit make sure to install suitable heat-sink to the MIC29152 chip. This circuit use 230V AC power source, so make sure to apply all the safety precautions while at the designing and testing phases.

In this design we use AT89S52 microcontroller to build inexpensive revs-per-minute meter. This meter can measure speed in the range of 1 to 9999 rev/min. This design was originally developed to measure the speed of brushless motors, but it can use for any application where the speed is in above mentioned range. In the given design input pulses are generated using Allegro A1203 Hall-effect bipolar switch and it can be replaced with any other Hall-effect sensor or IR detector. Current version of RPM counter is based on Atmel’s AT89S52 8bit MCU and control software is developed using MikroC 8051 compiler. At the time of implementation and testing we use Allegro A1203, A3517 and A3056 (for gear-tooth sensor operations) Hall-effect bipolar switches with this system and all these sensors produce excellent results with it. AT89S52 source code and complete circuit diagram of this project are available to download at google drive

In one of my project I need to access PC hardware ports using PHP. Standard distribution of PHP (PHP for Windows) may not have facilities to access PC/Server hardware ports, and finally I developed lightweight PHP extension to access server hardware ports. Current version of PHPhD (version 1.0.0.20) support for PHP 5.2.x (tested with PHP 5.2.1) and distributed under the terms and conditions of Mozilla Public License version 1.1. This PHP extension is available to download at http://elect.wikispaces.com/Downloads Using PHPhD users can access server hardware ports with minimum amount of coding and complexity. Example PHP source code which was based on PHPhD is listed in below, //Initialize and open hardware device driver if(!phphd_open_driver()) { die("Unable to open PHP hardware port access device driver"); } //read printer (LPT) port and get the curent port value $lpt_port_val = phphd_read_port(0x378+1); echo("LPT port value [0x378+1] : ". $lpt_po...

In this project we build CXA1619BS base high performance FM stereo radio receiver using low cost and readily available electronic components. In this design we use CXA1619 as FM radio receiver and BA1320 as FM stereo decoder and LA4108 as power amplifier. When building the circuit it is highly recommended to build it using the print circuit board (PCB) and take some necessary steps to reduce the effects of external interferences. In this design we use BA1320 as stereo decode and user can also use BA1330 with this circuit with some less amount of input voltage. (For example: +5V) We use BA1320 for this design because of its low cost, low complexity, higher channel separation and higher availability. In current design we use LA4108 as power amplifier and it delivers 6W x 2 output power at 8ohm load. While assembling the circuit make sure to apply suitable heat-sinks to both 7805 voltage regulator and LA4108 power amplifier. At the testing stages this circuit produces excellen...

After the 2 weeks of continues development we finally design suitable RC remote control system for cars. This RC system has, Battery eliminator circuit (BEC) Control System 433MHz transmitter and receiver module Motor driver and servo controller In this design both transmitter and receiver modules are based on seeed studio’s 433MHz RF link kit and control systems are based on microchip’s PIC16F84A MCU. At the design time we test this circuit with Futaba, Airtronics, JR-Radios, HiTec and "Mystery" (available in eBay) micro-servo units. This circuit may support standard electric motors (brushed DC motors) and during the testing stages we drive RC helicopter motors and RC airplane motors successfully with this system. To drive this circuit we use 7.2V 500mAh Li-Po batter pack. During the circuit assembling and testing, make sure to take necessary actions (e.g: shielding) to prevent/minimize the EM interferences which was generated by the motors. Most of the time t...

Most of the times finding the electronic parts in Sri Lanka is ( extremely ) difficult process. Lots of electronic part suppliers have fast-moving electronic parts only. (such as general resistors, capacitors, semiconductor devices related to the Hi-Fis, TVs and general consumer electronic products, etc.) For my electronic experiments I'm getting most of these “uncommon” electronic parts from following suppliers, Farnell : Farnell is my "number one" choice for most of the “uncommon” electronic parts and instruments, specially semiconductor devices and test instruments. Compared with other suppliers there prices are bit high but also had a nice service and higher reliability. Most (all ?) of there parts are coming from reliable and popular vendors. Most interesting thing is “There are no minimum order quantity levels in there orders”, which means I can order 1 unit of electronic part from them. Orel Corporation (Pvt.) Ltd. Bay: 12-13.Trace Expert City, Tripoli Squar...

Logic probe is an essential item for digital electronic fault findings and constructions. In this project we design compact and simple logic probe with digital pulse generator. This circuit is based on 4069 logic inverter and 7805 voltage regulator. In this design we use 4069 invert module to drive the LED of logic probe and to build the oscillator circuit. We use TO-92 style of 7805 regulator to drive the 4069 chip and entire circuit can be build around 2.5cm x 12cm PCB (if you need to reduce the size in to more, use the SMD version of 4069 and 7805) All the resistors are 1/8w and SMD versions are also acceptable. To change the period of pulser modify C1 or/and R2. Complete schematic of digital logic probe with pulser is available to download in here .

In this project we developed 1.5A, 3V to 27V adjustable power supply unit based on LM723 voltage regulator IC. In this project we add some additional options to standard LM723 PSU circuit (available from National Semiconductors) to improve the safety and performance. When assembling the circuit it is necessary to attach suitable heat sinks to both 2N3055 transistors. Single heat sink for both 2N3055 are also acceptable. According to the initial design R8 must be 0.39ohms (5W), but most of the people say it is bit difficult to get 0.39ohms locally (Sri Lanka) so I change value of R8 to 0.47ohms (5W) and it is available in local market. During the testings and usage this system produce an excellent results for us. Complete circuit diagram of the power supply unit is available to download in here .

This is simple PIC microcontroller base project to generate Morse codes using standard PS/2 keyboard. This project based on Microchip’s PIC16F73 microcontroller and National semiconductor’s LM386 audio power amplifier. Software for PIC microcontroller is written using MikroC and all the source codes, schematic diagrams and other documents are available to download at here . In this project we choose PIC16F73 because of it’s 4KW (KWords) program memory, it is possible to replace this MCU with any suitable MCU which having 4KW (or more) flash memory. (For example Atmel AT89C4051-24SJ with different source code, Microchip PIC16F648 with some minor changes in source code, etc) Audio power amplifier of this project is based on National Semiconductor’s LM386. We choose LM386 because of its lower power consumption and compactness. User may also replace this module with suitable power amplifier (for example Philips TDA7052, TDA8551, National’s LM4906, etc.) PIC16F73 software is develop...

In this project we developed user programmable automatic night light using Microchip's 8bit MCU – PIC12F675. In this design user may be able to program and store the time duration of the master light. Compared with other designs this circuit use transformerless power supply, and TRIAC to control the master light. Complete MCU software source code, operating guides and circuit diagram of this project is available to download at here . To get more information about transformerless power supply please refer the Microchip application note AN954 , and ST application note AN438 for MCU and TRIAC interfacing.

3.3V is now widely used in electronic circuit projects (especially in digital electronics). These days several MCUs, CPUs and Digital interfaces (e.g: USB, Ethernet) uses 3.3V and in this project we developed suitable compact power supply unit for these projects. This project is mainly based on National Semiconductors LM1086-(3.3) power regulator. With the suitable transformer this circuit may capable to deliver 3.3V (during the testing stages we get 3.29V) with 1.5A of maximum current. If you need more current please use LM1085 (3A) or LM1084 (5A) instead of LM1086 (U1). All the circuit diagrams and PCB patters for this project are located in here . To get the maximum performance, replace C2 and C3 with 10MFD/25V tantalum capacitors. Please note that it is necessary to install good heatsink to the LM1086-3.3 (U1) regulator.

In this project we develop automated telephone remote control system to demonstrate the functionality of MT8870 DTMF decoder. This project mainly based on MT8870 DTMF decoder and ATtiny2313 MCU. When this system connects to the phone line it monitor the status of the phone line and take the control of phone line when it detects the ringer, after that user may be able to control specified I/O port using appropriate keys. Finally user can issue predefine key combination to shutdown the phone line. Schematic diagram, source codes for ATMEL ATtiny2313 are available in here and all the source codes are developed using WinAVR (with Atmel AVR Studio 4). Please note that this project is developed for demonstration purposes only, some of the system states may not handled with the given source code.

These days we are working with VIA Technologies PC-1 series mainboards and compared with standard main boards these boards have special features and advantages. Main advantage is, its lower price and low power consumption . Like most modern motherboards these boards also have built-in Sound cards, Network adapters, SATA Support and build-in Video interface. VIA PC-1 series is specially design for low power computing and users may be able to run this mainboard with 150W power supply. There are several PC-1 mainboards are available and we are mainly worked with following units, PC-1000 Mainboard Powered by VIA C3 – 800MHz microprocessor 100/133 MHz FSB DDR-I Memory up to 1GB. VGA up to 64MB 4 USB 2.0 ports 10/100 LAN interface 1 PCI Slot Realtek AC97 audio codec Mini ATX form factor (170mm x 170mm) Price : Rs. 5000.00 (Sri Lanka Rupees) PC-3500 Mainboard Powered by VIA C7-D – 1800MHz microprocessor 400/800 MHz FSB DDR-II Memory up to 2GB VGA up to 256MB 6 USB 2.0 ports 10/100 LAN inte...

Prithvi Development Studio is my new project to build an IDE for GCBASIC – PIC Programming language. Prithvi is developed using Borland Delphi 7 programming language and currently it supports over 300 PIC Microcontroller devices. This IDE is based on GCBasic, and GPUtils, so users can directly produce hex files from Basic source code without using any 3rd party tools. (e.g: without using Microchip’s MPLAB - ASM). Current version of Prithvi Development Studio supports wide range of PIC 10F, 12x, 16x and 18x devices and Prithvi Development Studio also ship with wide range of GCBasic support libraries such as X10, LCD, ADC, RS232, USART, EEPROM, etc. Current version of Prithvi Development Studio has following features, Source code editor with syntax highlighting Intermediate code (Assembler), Hex code viewer Automatic completion, suggestions and parameter information Installable library system Project manager and source explorer to speed up the development process Inbuilt help viewer To-D...

In this project we decide to implement simple ATMEL AVR microcontroller programmer for our hobby electronic purposes. We get ideas for this project from http://www.electronics-diy.com and http://www.societyofrobots.com . All the credits of this project go to them and creator of the ISP Programmer - Adam Dybkowski. You can get complete circuit diagram from here Entire project is based on the 7408 - Quad AND gate chip and it is possible to use any (CMOS/TTL) AND gate chip with this project. During the testing phase we use CD4071 and 7409 quad AND gate chips without any circuit modifications. During the assembly process make sure to install proper heat-sink to the 7805 voltage regulator. After constructing the circuit download and install ISP Programmer and follow these steps, Open ISP Programmer software package and press "Setup" button to setup the programmer. Select "AEC ISP" as a "ISP Cable Pinout" and press OK Connect MCU to the programmer and power on...