This circuit detects the dial tone (DTMF Tone) from a telephone line and decodes the keypad pressed on the remote telephone. The dial tone we heard when we pick up the phone set is call Dual Tone Multi-Frequency (DTMF). The name was given because the tone that we heard over the phone is actually make up of two distinct frequency tone, hence the name dual tone. The DTMF tone is a form of one way communication between the dialer and the telephone exchange. A complete communication consist of the tone generator and the tone decoder. In this article, we are use the IC MT8870, the main component to decode the input dial tone to 5 digital output. These digital bits consists of pressed key code 4-bit and 1-bit to tell that data is available. It can be interface to a microcontroller for further application such as remote control, IVRS (Interactive voice control systems) etc. Continue reading DTMF Decoder MT8870
The keyboard matrix is the arrangement of circuit connections between the keyboard controller and all the keys on the keyboard. Each key does not have its own dedicated circuit; instead, each key is placed at the intersection of a matrix row and a matrix column. The keyboard repeatedly applies current to each column in turn, and checks to see which rows output current. From this, the keyboard can deduce which keys in that column have been depressed. The matrix takes the form of a printed circuit, either on a conventional PCB, or on membrane sheets. Continue reading Matrix Keypad Interfacing with Arduino
In this tutorial we will learn How to interface 16×2 LCD display using arduino. LCD displays available in various sizes 8×1, 16×1, 16×2, 16×4, 20 Char x 4 Lines. These all displays can be interfaced using this tutorial. We are more focusing on 16×2 LCD. It is commonly used.