You might find yourself needing a low power H bridge for driving a motor like I once did. The 555 IC can drive a load up to 200mA, source or sink, which might make is usable as a driver, if one can control the output as desired.
555 / 556 H bridge – [Link]
A certain knock at the door may tell you if the person behind it is the one expected or just somebody else. Each knock on the door itself cannot tell you too much, it can be lighter or stronger and that’s all about it, there’s no information on pitch here. But a certain sequence of knocks can be an actual secret code. The secret knock is encoded in the actual timings of the knocks, the time between each knock creating a distinguished pattern.
Secret knock detector with 555 – [Link]
One of the applications of 555 timers is a class D amplifier. In its most simplistic form it can be built with a single 555 and the 200mA current capability is enough to drive a small speaker, making it a good replacement for a low power amplifier. But I wanted more; I wanted to use it to build an amplifier that had enough power to allow listening to music in a small room. Adding a high power stage to a classical 555 class D amplifier was too easy, so I decided to build my own high power 555.
555 class D amplifier - [Link]
This entry for the 555 timer contest is from Andrew Smith who built a motion activated switch for a digital camera. The 555 timer is operating in monostable mode which is triggered by a PIR sensor when motion is detected. The monostable output of 555 then activates the camera through a remote.
555 Contest Entry: Motion activated camera – [Link]
555 timer based AM radio receiver published on Tube Time is one of many entries for the currently running 555 contest. This project uses a 555 timer as AM demodulator plus amplifier to drive the speaker. The radio signal is tuned with an LC tank circuit. The 555 timer is configured as a PWM where a ramp signal is created with a capacitor and a potentiometer. The radio signal picked by the LC circuit is superimposed on the ramp signal which varies the duty cycle of the output PWM wave. The variation in the duty cycle corresponds to the audio signal in the radio waves.
555 Contest Entry: AM radio – [Link]
In this Countdown Timer project, a 555 IC, a counter IC and a transistor switch to activate a relay either ON/OFF(mode selected by a jumper) as soon as the counting period is over. The circuit consists of an oscillator, a ripple counter and two switching transistors.
Simple Count Down timer Project – [Link]
Makerdino shared his light controlled screamer with 555 chips. [via]
Here’s a fun project to make with the 555 chip. It can be built as a stand alone circuit or you can put it inside a doll, toy or whatever! I’m entering this one in the 555 Contest in the Art category.
Light controlled screamer with 555s - [Link]
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]