Rajendra Bhatt explores a method of interfacing with a keypad via a simple 555 timer. The result is a two wire interface for 16 buttons.

There are other methods which do not require as many components, such as Jon Chandler's 10 Keys on One Port Pin. Although Rajendra's approach is not often seen and he gets good points for originality!

Attached are images of the project, including a schematic of the 555 interface.

The 555 timer has been configured as an astable multivibrator. It's output frequency varies based on the active resistance. With R1 and C as fixed components, each key has a resistor which acts as a switchable load (altering the output frequency accordingly).

The microcontroller can then read the output frequency to determine which key was pressed. The more I think about it, the better Jon's solution sounds. Still, its somewhat original. [via]

The simplest idea can sometimes be the best..

[via]

Bruno Gavand developed a PIC PAL library for displaying information on TV screens. The source code is written in MikroC, and has routines for video control, set pixel, fill screen, draw line/circle/box/character/string amongst others.

He has included plenty of example usage type programs along with circuit info and great code commenting. [via]

Johnny Chung Lee combines a cheap netbook and an iRobot Create, to create a video chat robot for around $500 that lets you move around distant places as if you were walking around. These are sometimes known as telepresence robots and cost several thousand dollars. [via]

This project resulted with a simple distance measurement tool which uses an AVR at the core along with and LCD and ultrasonic sensor.

The developer wanted a bar-graph and plain text to visualise the distance to an object, and include a "tare" function so that predefined distances could be added/subtracted to the result based on the tare distance. The source code, construction and interesting highlights are discussed in his article. [via]

This LED Clock was built by Simon Inns for his office. The display has 128 LEDs configured in a matrix configuration (16x8) and there's an onboard RTC and temperature sensor. [via]

Various project images including construction, PCB layout and the schematic.

Original MB Simon game

Simon Inns builds a MB Simon game clone using a PIC12F683 microcontroller (the original version shown right). His software supports full emulation of the original 'game 1' mode and includes the ability to select from four skill levels which control the number of colours you must repeat in a sequence in order to win the game. [via]

Alan Yates shares a possible entry for a 555 art competition. He calls the design "Araneae Junkboxius". A fun, easy project that is well suited for harnessing those soldering skills and creative touch. [link]