Dilshan R Jayakody’s Web Log

This post describes our initial attempt to design an automatic Zener diode tester. This tester is designed using well-known ICs such as MC34063 and PIC16F88 . Output for 5.1V Zener diode. This unit is capable of identifying Zener diodes up to 27.5V. Apart from that, it can be used to recognize leads of the diodes / Zeners and detect damaged diodes. For this project, we use components that are already in our inventory. Most of these components can be replaced with more accurate and modern substitutes. This unit provides approximately 5% to 15% accurate readings. Based on our observations, the accuracy of this unit can increase by using resistors with 1% tolerance, stable booster circuit, accurate sampling method(s), and with a more optimized PCB layout. Prototype version of Zener diode tester The schematic, PCB design and firmware of this project are available to download at github.com .

The main objective of this project is to design a maintenance free and low-cost light which automatically turns on and off at the predetermined time of the day. To meet the above requirement I designed this controller using ATmega8 MCU and DS1307 RTC. The driver stage of this light controller is intended to work with commonly available 7W LED modules. PCB of the programmable light controller. The core component of this programmable light is ATmega8 low power CMOS microcontroller. The main reason to select this microcontroller is it’s lower cost and higher availability. Except for the above two reasons this microcontroller also bundled with a rich set of peripherals which including 23 GPIOs, 3 independent timers, Two-wire serial interface, EEPROM, etc. Apart from ATmega8 microcontroller, this system uses DS1307 real time clock to maintain system time. Like ATmega8, DS1307 is also a very popular RTC in the market. This controller is designed to work with a 24V DC power supp...

This project is about USB port base true hardware random number generator and it is design around the avalanche noise which occurred in reversed biased P-N junction. This random number generator is design using commonly available electronic components. The core component of this system is Microchip’s PIC18F2550 microcontroller. The noise source is 2N3904 (Q1) transistor and LM386 low voltage power amplifier is used to amplify the incoming noise signals. This peripheral is design to work as a self-powered USB HID device. Cumulative distribution graph of random number sample In this design we use 2N3904 as a noise source because it give more noise amplitude than any another transistors which we tested. Theoretically this transistor (Q1) can be replaced with any other suitable NPN transistor like BC548, BC107, 2SC945, etc. The control software of this system is available for Linux and it’s compiled as x86 - 32bit binary file. This controller application required libusb driver ...

In this project we develop easy to build Microchip PIC development board for widerange of PIC Microcontrollers (which include 40pin Microchip PIC16 and PIC18 devices). This development board contain only the switching regulator (to generate +5V DC from the input power source) and RS232 serial port interface. The switching regulator of this development board may support input voltage of +8V to +25V DC. RS232 Serial interface of this development board is based on Maxim's MAX232 driver/receiver IC. This given design have 6 two-way jumpers to select crytal osciliator, MCLR and RS232 Tx/Rx terminals. While at the protyping stages we test this board successfully with PIC16F887, PIC16F877/A, PIC18F452, PIC18F4550 and PIC18F4620 MCUs. Diamensions of this PIC Development Board is 110×85mm. Schematic, PCB design and some of the related documents of this project are available to download at google drive .