Dilshan R Jayakody’s Web Log

Adjustable dual-rail power supply is an essential utility for analog electronic experiments. In this post we illustrate extremely simple, adjustable dual-rail power supply using LM317 and LM337 voltage regulators ICs. This PSU delivers 2A ±1.35V to ±18.5V output and thanks to 3 turn linear potentiometers output can be adjustable up to 2nd decimal point. Wiring diagram of dual-rail PSU The PCB of the PSU is simple to design and compact (65mm × 50mm). Both LM317 and LM337 need at least 60mm × 55mm or larger heat sinks (and both of these heat sinks need to be electrically isolated). The PCB and schematic of this PSU is available to download at here .

Intel HEX is an open file format to save machine code data. Today lot of compilers and EEPROM/Microcontroller programmers support for this file format as de facto standard. hex2file is a lightweight, command-line driven application to view and convert Intel HEX files into other file formats. I developed this application as a supporting utility for our on-going compiler/virtual machine projects. This utility supports four output formats which include CSV, plain- text, binary and numerical-text. hex2file standard numerical output in screen mode hex2file is an open source - free software and its available for both Linux and Windows operating systems. The latest version of hex2file utility is available to download at sourceforge.net – hex2file project page . The more details including project documentation are available at hex2file.sourceforge.net .

Nichrome-Wire Cutter is an essential tool for model aircraft constructions. We mainly use Nichrome-Wire Cutters to fabricate model aircraft wing assemblies, other than that Nichrom-Wire Cutters are used to cut wax, polystyrene materials and other similar kind of materials. In this project we construct electronically Controlled Nichrome-Wire Cutter. The main feature of this cutter is its (non mechanical) variable temperature controller. The temperature of the Nichrome-Wire is controlled using TL494 PWM controller. In this design TL494 is oscillated with fixed frequency and only varying factor is its duty cycle, in this given design R2 is used to control the duty cycle of the frequency. Duty cycle variation with R2 potentiometer This Nichrome-Wire Cutter requires 8V to 20V – 3A DC power source and 16.5V – 3A is recommended supply for this system. When constructing this system makes sure to solder and connect all the components properly, improper connections may cause oscillatio...

This is a quick post regarding my Commodore64 Power Supply restoration. This C64 is my first computer and two days back its power supply get burn because of some short circuit in its output connector. This is a first time I open this C64 PSU and its internal circuitry is really simple to track down. Commodore64 Power Supply Unit Main component of this PSU is its 6 terminal step-down transformer. Other than that its circuit it limited to 2 rectifier diodes, 7805 positive voltage regulator, 2 - 1W resistors and 4700 µF /16V electrolytic capacitor. In my C64 PSU, defective component is 7805 voltage regulator, once I replace it and rewire the output terminal its starts to work again (like good old days). Commodore64 Power Supply Schematic Above diagram illustrate the schematic of my C64 PSU (which I was traced using original PCB). The high resolution images of PSU, are available at my flickr photo collection .

This is an easy to build "liquid level monitor" and "automatic control system". This control system is mainly based on Microchip’s PIC16F630 8bit MCU and few combinatorial logic ICs. This system is specifically design for industries where there is a requirement of maintaining a liquid level at a particular level. The level monitoring stage of this system can capable to sense up-to 8 liquid levels and its trigger point can be programmed at anytime by using its simple 2 button user-interface. This system is design to work with 12V (or maximum of 25V) DC power source and its sensor system is capable of sensing liquids with resistance of up-to 30k to 35k. To minimize the sensor noise and output instability, the control software is equipped with simple 20-tap FIR like filter system. The output stage of this system is design to work with 12V to 24V DC relays and it is recommended to use Tyco K10 series or similar kind of relay with this system. The trigger point o...

LSI Computer System's LS7220 is a digital code lock system for automotive systems. This LS7220 integrated circuit is difficult to find in many places and because of that we design some alternative system which simulate the functionality of LS7220 code lock system. This simulated system executes on top of the PIC16F628A 8bit MCU and it release as an open hardware project. LS7220 is a "hard-wired" code-locking system, but this simulated system provides both "hard-wired" and customizable (re-programmable) code locking options. This re-programmable feature provides some higher degree of protection to the system and it allows user/administrator to change system’s code at any given time by without changing the wiring layout(s) of the system. Pinouts of Programmed MCU In this project PIC16F628A MCU use its internal 4MHz oscillator and because of that it doesn't require any external clocking source(s). This system is design to work with 5V DC power supply...

This is an easy to build high quality echo sound generator and it’s completely based on Princeton Technology’s PT2399 echo sound IC. This supplied circuit is specifically design to interface with electronic musical instruments (e.g: electronic audio synthesizers, electronic organs, etc.) and with microphone systems. This echo sound effect generator requires 12V - 25V DC power supply and it can deliver aprox. 20W output power (with 8 Ω speaker and 20V - 5A DC power supply). This given design of echo sound generator has 3 main controls, such as echo delay adjustment, echo-effect mixer and master volume control. This delay and mixing ratio is heavily depended on input source. Output of C1 note with maximum and minimum echo effects At the testing stage we test this system with lot of input sources. According to our experiments this system can product good results with slow speed music and it produce excellent results with the voices. When it comes to high speed music (with ma...