Electronic Basics #17: Oscillators || RC, LC, Crystal

if you've ever tried to find out just how fast your my controller can switch things on and off you might have thought to yourself where does this limitation come from or you might have thoughts what determines how fast my clock is ticking or what determines how often my multimeter refreshes its display values the answer to such timing related questions are so called oscillators basically an electronic circuit that can create periodic alternating voltage signals like a square triangle or side wave these are then used as a clock signal for device or as a carrier wave for radio communication or other data exchange through the air so in this video let's talk about the most popular oscillator types which you can also easily build at home let's get started first off relaxation circuits especially with RC components this a stable multi vibrator is a classic and rather simple example the main principle is about using two capacitors c1 and c2 which get charged alternating full resistor to a certain threshold voltage of the transistor in this case around 0.3 volts this way the transistor becomes conductive and discharges capacitor c1 while the other one c2 gets charged one c2 then reaches the threshold voltage the cycle repeats with the other transistor and we successfully have created a rectangle waveform which is visualized by the LEDs if you would decrease the resistance or capacitance the charging and discharging process would get shorter and the frequency of the rectangle wave increases an icy year which also implements the same core idea is the always popular 555 timer these consists of two comparators 2 logic ends and more logic or gates and the rs flip-flop so not that easy to explain right now but on the other hand super easy to use by connecting a 100 nano farad capacitor a 680 ohm resistor and 150 kilo ohm potentiometer we can create a stable and variable rectangle wave again by charging and discharging the capacitor periodically in this case though the threshold values are 66 and 33 percent of the supply voltage and of course you can increase the frequency again up to a certain degree but eventually at some point it is not that pleasant to look at that is where we use LC resonators aka LC tank circuits to create very high frequencies but before going into detail about those I recommend that you should watch my videos about capacitors and inductors firstly the capacitor gets charged up to the maximum voltage and has its maximum electrostatic energy stored after disconnecting the power supply the capacitor slowly discharges through the inductor and since the current tuned inductor cannot change instantly it also slowly builds up until the coil has reached its maximum of stored magnetic energy this energy then converts back into the electrostatic energy of the capacitor by charging it up in Reverse and the cycle repeats again simultaneously we also created a sine voltage and current along the way but in reality here this oscillation does not last that long because parasitic resistance is everywhere and converts some of the power into heat we also see here that the tank circuit oscillated with a specific frequency which is called the resonant frequency this occurs when the reactance of the coil and capacitor are the same and cancel each other out as a consequence the voltage or current in an LC circuit can exceed the initial applied values of the power supply but only near the resonant frequency but that is not the main point right now we still need to find a way to feed the circuit energy at the right time so that the oscillation does not stop this can be achieved by connecting the outputs of the tank circuits to the input of an amplifier like this NPN transistor by choosing the amplification factor just right the output of the amplifier delivers a stable megahertz sine wave but as a side notes building such oscillators on a breadboard is not recommended due to rather loose connections and parasitic capacitance just like the RC methods we can change the inductance and capacitance to create all kinds of different frequencies necessary for different tasks but if we need even more stable frequencies we can also use a crystal oscillator it acts just like an LC resonator but also uses the mechanical vibrations of a piezo crystal and creates in this case a stable 16 megahertz signal the necessary amplifier circuits is very similar to the one before and you often see such crystals next to my controller to set its processing speeds and with that being said you already know quite a bit about oscillators I hope you learned something new if so don't forget to like share and subscribe that would be awesome consider supporting me through my patreon campaign to keep such videos coming stay creative and I will see you next time

Channel: GreatScott!

Views: 731,578

Rating: 4.9213018 out of 5

Keywords: Electronic Oscillator, RC Circuit, LC Circuit, RC Oscillator, Electronics (Field Of Study), tutorial, oscillator, electronics, electronic, how to, crystal, crystal oscillator, lc tank, LC tank, greatscott!, greatscott, circuit, astable multivibrator, 555 timer, 555, resonator, lc resonator

Id: eYVOdlK15Og

Length: 6min 1sec (361 seconds)

Published: Sun Nov 22 2015

Reddit Comments

[u/notHooptieJ]

I grew up with an EE dad in the 80s.. i wish videos like this had been around then.. its crazy now to watch one video and immediately unlock a whole slew of knowledge i didnt know i had locked away.

[u/brewderr]

just in time for my test tomorrow, thanks!