Dilshan R Jayakody’s Web Log

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 .