Dilshan R Jayakody’s Web Log

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.

Logic analyzers are allowing us to monitor and /or diagnose a large number of digital signals simultaneously and these devices are essential when developing complex digital systems. In this project we design simple 8 channel USB logic analyzer with Windows version of driver software. Design of this logic analyzer is based around Future Technology Devices FT245 USB FIFO chip. With the given oscillator this system takes 14MSPS (Mega samples per second) and this system is design to work as (USB) self powered device (without any external power source). Driver part of this project is based on FTD2XX driver and GUI is developed using Delphi. Current version of driver software is design to work with Windows NT operating systems and it is highly recommended to use it with 1360 × 768 or with higher video resolutions (with aspect ratio of 16:9). This design also contains real-time logic level indicators to monitor "low frequency" signal levels and construction of that portion i...

In this project we design 8 feet C band satellite dish antenna and some of its specifications are listed in below, Diameter of the reflector : 248.0cm F/D ratio : 0.391 Focal length : 91.5cm Calculated gain (Aprox.) : 40.23 dB Materials used for reflector : Aluminum sheets and Aluminum nets Number of panels (in reflector) : 4 units Materials used for Mounting mechanism : Steel Weight (Aprox.) : 40 - 45 kg (without antenna positioning system) LNBF : Generic dual twin C band LNBF Antenna positioning system : Using D.C motorized actuator

One of my friend had Sony PlayStation 2 (SCPH-39000 series) game console and in few months back it get fail because of the internal short-circuit due to spill of some liquid over the game console. Finally he sends it to me to repair it, and I found some problems in both PSU (Power Supply Unit) and motherboard of the console. In first round of the repair I replace IC807 (78M05), PS013 fuse and all the related parts near that area (because I notice some burn marks in that location) except IC806 (NJM12904). Other than that I replace R278 (1.5k), R279 (1K + 100R), R491 to R495 (with wire links), R470 (100K), Q415 (2SC2873), Q406 (IRF7901, I got this transistor from another old PS2 game console main board, available in junk store), F001 (with some 42 S.W.G copper wire) and D404 (with 3 × 1N4148 diodes). When I replace and re-solder some of the parts as described above, I got the video signal (PS2 startup splash and main menu) from the console. But system may not produce any audio signals (i...