This project was designed and implemented an electronic phone directory which has a built-in automatic dialer. The electronic directory allows user to Dial, Enter, Search and Delete entries. When dialing, the Atmel 8515 microcontroller will generate the Dual Tone Multi Frequency (DTMF) signals corresponding to the phone number being dialed. To avoid building the phone circuit for the dialer, a DTMF decoder was used to detect what number is dialed by the user.
Electronic Phone Directory and DTMF Generator:[Link] - [Via]
“A metronome is any device that produces a regulated audible and/or visual pulse, usually used to establish a steady beat, or tempo, measured in beats-per-minute (BPM) for the performance of musical compositions. It is an invaluable practice tool for musicians that goes back hundreds of years.”(wikipedia about metronome)
Basically the project consists of 3 resistors, 2 capacitors, 2 led’s, a speaker and the 555 IC so its not much that can go wrong. I recommend this project to beginners, you can either fabricate a PCB for it or just assemble it on a breadboard.
It seems generating sync-ed sound and video on AVR its not that easy. AVR Atmega88 microcontroller is clocked at 20MHz and so it generates 45 full VGA display lines at almost 60Hz frame rate. Sound is generated during VGA horizontal blanking periods. That gives a sampling rate of 31496kHz which is enough for good chip-sound quality. Sound player is capable to play four sound channels. And all that beauty is programmed in pure assembly language for best performance.
Generate Sound and Video on the same AVR chip:[Link] - [Via]
This is a very small telephone exchange system with two ordinary telephones attached. Full bi-directional facility with an intercom system: when a phone is in off hook condition , the circuit will detect it & send ringing pulse to the other phone. When it will be picked up , the connection will be established between both phones. This will take place vice-versa also. This project sounds great if you need a simple and efficient communication system, like in a tree house, you place on telephone in the tree house and the other one in your house. This is just an example but there are far more applications for this system.
CMoy is a very simple and portable headphone amplifier. The amplifier was originally posted by ChuMoy on headwize.com. Headphones amplifiers are usually used when the output of a device is to low for the kind of headphones you’re using, or to get better sound quality by keeping the device on a medium volume setting and amplifying the sound with the headphone amplifier. I’ve not build this amplifier so far, so i cant tell you from my personal experience if it sounds good or bad, but from what i read on the internet, users that build it are very happy with the results. The schematic is very simple, parts are easy accessible so it should go really smooth with the building process if you decide to do it.
