Tone generator

Summary

The tone generator's function is to produce different frequency sine wave for each digital word applied to its input. This project allows the computer to sweep the instrument under test through the desired frequency range. It can be adapted to create a Morse code circuit, by adding a switch to the output. The circuit here is based upon 555 as a free running multivibrator. Shown below is internal structure of a multivibrator IC and its circuitry.
NE555

Description

 

 This tone generator circuit is based on 555 timers, working as a free running oscillator. The frequency or pitch of the tone is set by the resistors and capacitors situated in the left side of the circuit. The capacitor is used to reduce noise or undesired signals for smooth operation of potentiometer.

 

The tone generator overturns and buffers 8 data lines from the computer. By the use of a D/A (digital to analog) converter and a current to voltage converter, the digital word is converted to a D.C. voltage. An 8-bit frequency control word is used here as it allows 256 frequencies to be selected.
 
Here we are presenting some Morse code for the reference so as to generate it just by adding a switch to circuit described above.
Tone Generation

Circuit Diagram

Components
Resistor Image
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 Resistor

Resistor is a passive component used to control current in a circuit. Its resistance is given by the ratio of voltage applied across its terminals to the current passing through it. Thus a particular value of resistor, for fixed voltage, limits the current through it. They are omnipresent in electronic circuits.

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Capacitor image
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 Capacitor

 

 

Capacitor is a passive component used to store charge. The charge (q) stored in a capacitor is the product of its capacitance (C) value and the voltage (V) applied to it. Capacitors offer infinite reactance to zero frequency so they are used for blocking DC components or bypassing the AC signals. The capacitor undergoes through a recursive cycl...

Speaker Image
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 Speaker
A loudspeaker (or "speaker") is a transducer that converts electrical energy into acoustical energy. When an electric signal is applied to the input pin of speaker, it generates sound waves. The other pin is connected to ground. A speaker is commonly used to produce sound in response to a sensor output. For example, in an...
555 Timer | IC 555 | NE555
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 555 Timer IC

555 is a very commonly used IC for generating accurate timing pulses. It is an 8pin timer IC and has mainly two modes of operation: monostable and astable. In monostable mode time delay of the pulses can be precisely controlled by an external resistor and a capacitor whereas in astable mode the frequency & duty cycle are controlled by two external resistors and a...

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