Dilshan R Jayakody’s Web Log

In this project we develop 32W hi-fi audio power amplifier using TDA2050 integrated circuit. The main objective of this project is to provide common high gain audio amplifier for DIY kind of projects. In this given PCB pattern, both the power amplifier and PSU are limited to the 53mm x 65mm printed circuit board. This circuit is design to work with 15V – 18V (AC) supply voltage and it is highly recommended to use suitable step down toroidal transformer with this system. All the PCB patterns and schematic diagrams of this project are available to download in google drive .

This DIY project happens because of some request of my family members. The ultimate goal of this project is building analog TV antenna to receive UHF and VHF channels with minimum distortion, noise, materials and time. All the building materials of this antenna are available in general electronic shops and hardware stores. I got excellent results from this antenna in my home town: Maharagama ( Colombo , Sri Lanka) with all the locally available VHF and UHF channels. Technical drawing of this antenna is available to download in here .

In this project we design low cost high performance programmable home security system using few LDR’s as an input sensors. When above sensor(s) get triggered system may dial the user specified phone number (using build-in DTMF generator) and activate the high power audio alarm and lights. All the parameters of DTMF generator, audio alarm and light interface are programmed through the RS232 serial interface. Current firmware of this system presents interactive control system through the RS232 interface. This control system consist with the menu driven configuration options, self tests, system report generators, etc. This system also contain 5W (with 4Ω speaker) audio alarm with three selectable tone configurations, which include Police siren, Fire engine siren and Ambulance siren. This system uses a Microchip’s PIC16F877A as a main controller, LM339 as sensor interface, UM3561 as a tone generator and μPC2002 as a speaker driver (audio amplifier). LM7805, LM7812 and LM317 voltage...

While designing some mechanical projects we often have need for easy to build motor speed controllers. Thanks to the SGS-THOMSON Microelectronic’s TDA7274, now we have easy to build, low voltage D.C motor speed controller. TDA7274 provides wide operating voltage range from 1.8V to 6V and in this project we use it to drive small CD-ROM ejection motors. In this project we design entire speed controller with 39.3mm × 28.9mm PCB. While at the prototyping we test this system with 5V power source and successfully control several CD-ROM ejection motors, cassette motors and toy D.C motors. You can obtain all the circuit diagrams, PCB patterns and other information of low voltage motor speed controller from google drive .

In this project we design 2 channel D.C motor controller with pulse width modulation (PWM) based speed and direction control. This module is mainly design to drive 14.4V to 18V electric D.C motors. This motor controller is design to work with 18V - 1.5A D.C power source and it can be directly interface with general microprocessor / microcontroller system (without using any voltage level shifters). While at the prototyping stages we successfully couple this module with several NIDEC D.C fans and blowers which include D1751M24B7AP, E1331K12B7AZ-00, DME37KA, CF24DM506, etc. Control interface for this module is easy to use and at the designing stages we interface it with PIC16F887 and Atmega64 MCUs. Control interface of this module is consisting with 3 inputs (please refer the J3 in the circuit diagram) and using these inputs user may be able to select the motor, apply the brakes and also change the rotational directions of the motor(s). When constructing the circuit it is recommend...

In this article we demonstrate how to processing OpenOffice.org dictionary files using Lazarus – FPC IDE. To use the OpenOffice.org dictionary first we need to extract AFF file and DIC files from the OXT (OpenOffice.org extension) file. This can be easily done using 7Zip or any other generally available file archiving utility. (Only thing we need to do is change OXT file extension to ZIP and extract the contents) To process this dictionary (DIC) file we need to use affix table defined in the AFF file. In this sample code we implement the complete AFF and DIC file processor for English (United States) dictionary of the OpenOffice.org. Our processing of this affix file in this sample application is based on the following rules, AFF file generally consist with some conditional modules as follows, SFX T N 4 SFX T 0 st e SFX T y iest [^aeiou]y SFX T 0 est [aeiou]y SFX T 0 est [^ey] In the first line " SFX " means ...

I have Panasonic DMR-E55 DVD Video Recorder and suddenly it start to get reboot when the system performs “Self Checking”. Because of this reboot problem I may not be able to record DVDs and need to put some extra effort to eject the disks. Most of the times this reboot occurs in cyclic pattern and to break this cycle I need to be eject the DVD disk manually from the system. While examine the system my primary attention moves on to the “Digital RAM card” of the system (Because it actively involves in to the DVD burning process). But after the 2 weeks of continues inspection I found that the problem is in the SMPS primary chip - STR G6535. After replacing the STR G6535, system starts to work in an order. Replacement of this chip is not a complex process but while doing that it is necessary to put some attention about the SMD components located nearby.