Here I wanted to write a record of my works and how they relate to each other. I have arbitrarily started a topic stating that any electronics circuit has a signal source and power source. Here it is outlined how and what types of signal are generated in electronics circuits. We distinguish the signal in terms of shape and oscillation used. We also discuss how the signals are actually generated, what actual components are used. That is transistors, operational amplifiers, Timer IC or from microcontroller etc.
Digital Signals and Analog Signals are two fundamentals types of signals used in electronics and communication systems. Other than that you have the power supplies.
Another classification of signal would be harmonic oscillator and relaxation oscillator generated signals as explained in details in types of oscilllators. In brief the difference is that harmonic oscillator generates pure single tone sinusoidal signal while the relaxation oscillators generate rectangular or square wave signals. Rectangular signals could be for example PWM signals(see Arduino Fast PWM) that can be generated using microcontroller or microcontroller boards like Arduino. Remembering that a square wave signal consist of high number of sinusoidal signal and therefore one uses low pass filter(see Sallen Key low pass filter calculator) to block the high frequency components to convert the square wave signal to sinusoidal signal. This was illustrated in the sine wave generator arduino tutorial.
Example of harmonic oscillator are crystal colpitts oscillator, wien bridge oscillator using op-amp 741, twin t oscillator. Harmonic oscillators are used in RF circuits in analog radio communication systems such as in AM(see arduino AM radio receiver), varactor diode FM modulator circuit.
Example of relaxation oscillator includes astable multivibrators that can be designed using transistors, op-amp and timer IC 555. The circuit diagram and operation of these design methods are explained in astable multivibrator using transistors, astable multivibrator using op-amp and, astable multivibrator using 555 Timer IC.
Astable multivibrator generates square wave and therefore also called square wave generator or clock signal generators in digital electronics circuits. The frequency of such square wave signal or clock signal can be measured using do it yourself or diy Arduino frequency meter. The arduino frequency counter or meter can also be used to measure for example the square wave generated from ATmega328p CTC mode. Doing this you can exactly know whether the arduino frequency meter is accurate or not. To help you calculate the count value to be set for given desired frequency you can use the online AVR timer calculator.
