Monday, February 23, 2009

3.3V – 1.5A Compact Power Supply Unit


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.

Tuesday, February 17, 2009

Automated Telephone Remote Control – Demonstration

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.

Tuesday, February 10, 2009

Low cost and low power VIA PC-1 Series mainboards

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 interface
  • 1 PCI and 1 PCIExpress x16 Slot
  • 2 SATA Connectors
  • Realtek 6 channel audio codec

Price : Rs. 8500.00 (Sri Lanka Rupees)

During the testing phase we use PC-1000 with Fedora 9 and Windows XP, and PC-3500 with Windows Vista, Windows XP and Windows 7 Beta. Both mainboards provide excellent performance with following configurations,

  • Memory - 1GB (DDR/DDR-II)
  • Power Supply - 150W (20 pin)
  • Disk Drivers - 80GB IDE
  • Input Devices - PS/2 Keyboard and Mouse
  • Operating System - Windows XP Media Center Edition

We use PC-1000 mainboard for our control system experiments with slight modifications and it produces excellent results with following configuration,

  • Memory - 512MB DDR-I
  • Power Supply - 36V homemade PSU
  • Disk Drivers - N/A
  • Input Devices - PIC MCU base homemade Keyboard simulator
  • Operating System - Windows XP using Flash Drive (Build using BartPE)
  • USB Device - 2GB Kingston Data Traveler - USB Flash Driver.

PC-3500 is recommended for intermediate level home PCs.

Friday, February 6, 2009

Prithvi Development Studio for PIC Microcontrollers

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-Do list editor
  • User configurable programmer and tools section

Prithvi is an Open Source Free Software project and it is based on MIT Open Source License. You can download Prithvi Development Studio from http://prithvi.sourceforge.net.