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Theory of Matrix Keypad

Posted on February 13, 2011 by R-B One comment

Tact switches are widely used as digital input devices. Normally one tact switch requires one digital I/P pin of a microcontroller but if you want to interface a matrix of such switches (say a 16 digit keypad), assigning a digital I/O pin for each key won’t be a good idea. You need to think about the way to minimize the required number of digital I/O pins of microcontroller. A very popular method is a keypad matrix where the keys are arranged into rows and columns so that a 4×4 (16) tact switches can be interfaced to a microcontroller using only

MikroC Pro for PIC : Installation and Setup

Posted on February 12, 2011 by R-B 5 comments

My PIC tutorials and projects use MikroC compiler for firmware development. But I don’t think I ever posted anything on its installation and setup. Today, I am going to show how to install MikroC Pro for PIC (v4.60) on a Windows PC. First of all, download the zipped installation file from here, unzip it and run the setup program. Installation is straightforward. When you first start the MikroC compiler, it opens a LED blinking example project. You can close this project by clicking on ‘Close Project’ under Project menu.

Open source color video game development system based on AVR

Posted on February 10, 2011 by R-B Leave a comment

This project describes an open source color game development platform based on an AVR microcontroller. You can code a color, high resolution, smooth video game, like Super Mario Bros or Commander Keen on this system. All video processing is done by software in background using interrupts, with no external active components. You only need to connect the AVR to a RGB monitor. AVRs don’t have enough RAM for direct video memory, and therefore a TILE based graphics driver is used. In TILE, the display screen is divided into X*Y tiles and each tile graphic is addressed from reference table located in

A contact-less digital tachometer based on optical sensors

Posted on February 10, 2011 by R-B Leave a comment

A tachometer is use to measure the rotations per minute (RPM) of a moving shaft or a motor. An example is a digital tachometer in a car that gives the RPM of the engine. This tutorial shows how to build a digital tachometer using a microcontroller and optical sensors. The sensor unit consists of an IR LED that transmits infrared light and a photo diode that receives the light. This project uses a computer fan to demonstrate the technique. The fan is placed between the IR LED and the photo diode so that the blades of the moving fan interrupts

Heart rate measurement from fingertip

Posted on February 5, 2011 by R-B 841 comments

Introduction Heart rate measurement indicates the soundness of the human cardiovascular system. This project demonstrates a technique to measure the heart rate by sensing the variation of the blood volume inside a finger artery, which is caused by the pumping action of the heart. It consists of an infrared LED that transmits an IR signal through the fingertip of the subject. A part of this infrared light is reflected by the blood cells. The reflected signal is detected by a photo diode sensor. The changing blood volume with heartbeat results in a train of pulses at the output of the photo diode,

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