A matrix keypad uses rows and column arrangement of keys to reduce the required number of I/O pins for interfacing with a microcontroller. This article shows how you can use a 555 Timer IC to interface a keypad with just 2 connections. The 555 timer is configured in astable multivibrator where the output frequency changes with each key press. Based on how many times the Timer module overflows, the information about the pressed key is determined.
2-Wire Keypad Interface with a 555 Timer – [Link]
The story of the triple nickel. Jeri writes – [via]
In this video I go over some of the history of the www.555contest.com and how it grew from a few random events. I also demonstrate an AM transmitter that broadcasts tones depending on the temperature of a thermistor.
The Story of the 555 contest and Temperature to Tone Transmitter – [Link]
All AVR microcontrollers have internal watchdog timer that can be successfully used in your projects. Atmega328 and other modern AVR microcontrollers have so called Enhanced Watchdog Timer (WDT). It has few very useful features including: separate 128kHz clock source, ability to reset microcontroller and generate interrupt.
Using watchdog timer in your projects - [Link]
There is a 555 contest happening that was conceived by Jeri Ellsworth and Chris Gammell. Check it out. [via]
This contest came about in mid-January 2011 on Twitter. Jeri began talking about 555 timers and excitement built up enough to start doing something about it! The organizers of the contest have no monetary interest, only interest in seeing new designs and creativity blossom. Vendors/sponsors did not prompt this contest, though they are helping organize and providing prizes. Really we’re just looking to have fun and see new designs, so be sure to submit yours!
555 contest up and running – [Link]
Jimmy Proton writes:
In this instructable i will teach you every thing you would ever need to know about the 555 timer IC. If you already know about the chip you could check out my slide show titled “47 projects to do with a 555” it will teach you every basic project to use a 555 with, its great for beginners!
Learn about the 555 – [Link]
When teamed up with an oscilloscope, this simple circuit provides a means of measuring capacitor ESR. A 555 timer (IC1) configured as a 2.3kHz free-running oscillator acts as the timebase. It provides narrow (7.7µs) pulses to the capacitor under test via a NAND Schmitt trigger (IC2) and transistor Q1. A 100Ω resistor in series with Q1 limits current flow to about 50mA. Therefore, an ESR of 1Ω will produce pulses across the test capacitor of 50mV, which means that an oscilloscope with a vertical sensitivity of 5mV can measure ESR down to 0.1Ω or less.
Oscilloscope ESR Tester - [Link]
This is a timed digital switch. It uses a 16F84A PIC microcontroller to control the relay and it’s timming.
Timed digital switch – [Link]
Digital timers are used to operate electrical devices at specific times. This project describes how to make a programmable digital timer using PIC16F628A microcontroller. The timer has a relay switch to control an electrical appliance. The beauty of this timer is that you can set both ON and OFF time from 0 minutes to 99 hours and 59 minutes.
Digital Programmable Timer Switch – [Link]
This article discuss how to use the 16bit timer on Atmega328.
Atmega328 has one 16 bit timer which is more powerful comparing to 8 bit timers. 16 bit timer is called Timer/Counter1. Counter1 has twice more bits than 8 bit Counter0, so you get more counts leading to longer duration and more precise timings.
Programming 16 bit timer on Atmega328 - [Link]