Let's make a Voltage Controlled Oscillator (VCO)

Let's make a Voltage Controlled Oscillator (VCO)
In this video we create a voltage controlled oscillator with a 555 timer chip, two capacitors, a 33k resistor, and a 10k potentiometer.
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FAQ:
Me: Paul, 49 from USA
Education: United States Navy, University of California at San Diego B.S. E.E., University of Pittsburgh M.S. E.E.
Experience: United States Navy STS, Bayer Intnl Process Engineer, C.C.A.C AP of EE
Current: Retired
Health: BAD (Congestive Heart Failure)
Hobbies: Electronics, flying, amateur radio, music (classic rock)
Low cost, professional PCB's: www.pcbway.com

[@ph0enixr]

On the schematic you have the 33K resistor bridging 6 and 2, but in your actual circuit it bridges 6 and 3.

[@RavenLuni]

Its not 33K either - more like 18 ohms!

[@georgechambers3197]

I love 555 timers, have a whole bag and use them all the time. I really like the oscillator videos Hope your weekend was good!

[@mikeoliver3254]

Nice I'm going to have to dig out a 555 and play with this today.

[@junksmith_wizard]

ABSOLUTELY AMAZING I HAVE SAT HERE ALL DAY WITH NO LUCK AND THEN.... A MAN WITH A PIECE OF PAPER SHOWED ME THE WAY. THANK YOU DUDE!

[@learnelectronics]

Glad it helped

[@acestudioscouk-Ace-G0ACE]

Just what I needed to learn. Your style is such that I feel I'm sitting next to you and you are showing me one to one.

[@TigerClawTV]

I think I have watched this video like 3 times now. Fascinating stuff. Would love to have seen this circuit hooked to a speaker.

[@RickNuthman]

I was wondering the same thing - how to hook it up to a speaker

[@niklas2052]

​@@RickNuthman You can take the signal from pin 3 (the one he's showing on the oscilloscope) and feed it into an audio amplifier. Best to do this via another potentiometer, so you can vary the voltage going into the amplifier (start at 0 and turn it up until you hear something). Please note though that the schematic in the video is wrong (as others have commented here as well). As far as I can tell at least: 33k resistor should connect pin 6 and 3 (instead of 6 and 2), and pin 2 connects to ground only via the capacitor, not directly.

[@Linguae_Music]

@@RickNuthman just plug + into the output and put - to ground If its a small speaker should work :P Pull one out of an alarm clock or something :P This is the simple way lol

[@MichaelEckl]

I'd love to get into the math for this!

[@alfredtambunan8961]

You teach it very beautifully easy! My highest thanks to you!

[@davidglynnguitars8119]

Enjoy whatever time you can spend recharging!! Thanks for another great video!!

[@learnelectronics]

Thanks

[@matttodd9424]

Hi great video, going to make the circuit asap ,thanks Everyday 's a school day .

[@hhhgdgb5205]

A great demonstration , thank you really 555 is a magic ic

[@MalagasOnFire]

The 555 still reliable and simple, multipurpose time and that configuration also gives 50% dutty cycle at certain frequency range. About calculations yeah bring up to remember the integration / primitives and also electronics.

[@jeremycole3008]

i enjoyed watchin even though his schematic had two problems. but still a thumbs up

[@jamest.5001]

Great video. I discovered the 555 when I had the crazy idea if building a DC motor controller! For a big DC motor. Like for electric vehicles! I guess they need to be a bit more complex . than just a 555 and a ton of MOSFETs! I heard they will work. Just not likely for long. They need safty shut offs and current sensing. To keep from frying something! Keep up the good work,

[@cwebs1000]

I believe your drawing is wrong on pin 2. You have both legs of the cap going to ground

[@learnelectronics]

Cap between pin 2 and ground

[@sayantanmaiti2513]

Carl is right..actually it was a slight mistake. 2 will go to gnd via the cap..not directly

[@Egorleningrad]

Спасибо мужик!

[@CoolDudeClem]

Ah the humble 555 and it's many uses! If I had a penny for every time I've used one of these ... well you know. Must say that's an unusual way of wiring a 555, I haven't seen it done that way before but hey, it works!

[@davidglynnguitars8119]

If you had a penny for everytime you used one of these, you'd have to buy more with the pennies!! LOL!!

[@georgegates526]

Love the 555 IC's !!

[@tonyd1149]

Thank you for your videos.

[@melplishka5978]

As always ty my friend your knowledge is well received lol.

[@hebitsukai9830]

cool dude, best class, easy to understand, clear, magnificent, :D coolest grandpa in da world

[@VaansWorld]

Subscribed!! Thanks dude. You rock

[@Neffers_UK]

Those little pots are hellish in breadboard. The 555 is such a venerable chip. Since being a kid I have been aware of its virtues and I still cannot get my head round the lil fella properly. It did introduce the timing theory (using a capacitor and a resistor as a delay) though. I'm still stupid despite what I am aware of, trying my best to learn though, and even though the 555 has a billion pages on the internet it always good to see people like yourself continue to show it off. The algebra, yeah that really screws me up, but I don't think that a decent walk through would be detrimental, unless your older viewers (I'm new) oppose. Been watching your vids quite a bit, enjoyable.

[@RoryFrenn]

3:11 1/-The integral goes from -infinity to t 2/- f(t) = f0+k * Vin(t) not f(t) = f0+k - Vin(t) 3/-The s variable in the Laplace domain is complex frequency and not time in seconds. 4/-Laplace is pronounced /ləˈplɑs/

[@theredparty4853]

Clearly, he's not an Engineer.

[@agustinferrari1645]

Minute 6:51 - your capacitor is with both terminals to ground. You should change that schematic.

[@byronwatkins2565]

The 's' in a Laplace transform is NOT seconds; it is a complex variable analog of frequency.

[@teh60]

Any video with the 555 timer is interesting. Nice job Paul.

[@learnelectronics]

Thank you

[@woosix7735]

I know that this is a very simple circuit, but it would be pretty useful to make it so that changing the frequency doesn't change the duty cycle

[@SimpleEnough2k9]

Thanks Paul for the intro on 555 based VCO. I think there's a mistake in your schematic at 06:43 as both ends of the timing capacitor are connected to ground. Obviously you didn't reproduce the error on the breadboard otherwise it wouldn't have worked too well. Keep up with the good work !

[@learnelectronics]

Cap between pin 2 and ground

[@Sarahbuildsstepsequencers]

What is the value of the cap you changed before switching to the 2.2uF, please? Would be cool to see this hooked up to a cd4017 and some pots to make a musical sequencer. ☺️

[@roccorid]

Can we see some more VCO types? Thank you for your time.

[@NGinuity]

Yes, THIS.

[@roccorid]

?

[@NGinuity]

Rocco Rid Like you, I want more VCO videos

[@roccorid]

Yes!

[@alicekichlu215]

MAY I SUGGEST VIDEO PRESENTATION ON PLL.

[@IvanColmenero]

Hello! I just saw this video, very interesting. But, I have a question or comment; in your draw you "connect" pin 6 to a 33k resistor and to the resistor to pin 2. But, on the circuit I saw 33k resistor connect to pin 3 of 555 timer. I make a mistake what i saw...? or you can make the circuit in two different configurations? Thank's for the answer Mr. Paul, and sorry if i'm wrong.

[@nigeladams8321]

hell yeah brother!

[@payamreisi5591]

Was the Schematic ok ? Timing cap both leads to gnd?

[@3deeguy]

Thanks. I gotta build this circuit. I wrote a program for a 433Mhz module that was stable until I connected it to a DC motor. Commutator noise? I actually want to hear the instability when I connect the motor to it.

[@roccorid]

Just hook up a speaker and we are back to some nice synth experiments!! Can you expand on relaxaxion and harmonic concepts?

[@HazeAnderson]

Thanks for this video. If want more cool things to do with VCOs ... how about using one 555 VCO to drive another? Aka the Atari Punk Console with a 556 chip. Cheers!

[@danielwalker5682]

lovely.

[@Deatan76]

So to get lets say between 1kHz and 10kHz output frequency what should be the values of my resistor and capacitor?

[@auratone25]

How would I turn that to audio? Would it just be connected to the output of the voltage? Is there any good software to practice and learn with?

[@RoboMiller570]

Excuse me, @learnelectronics, I'm using a membrane potentiometer for my VCO. It has three male connectors going into F17, 18, and 19. Could I connect J17 and 19 into ground instead of A17 and 19 like how you have it? I'm afraid my potentiometer doesn't connect across the gap to E17 and 19 like yours. I'm new to circuit bending; thank you!

[@mu8502]

hey is there any way control vco with very low voltages like microvolts increasing the frequency ??????????

[@MrMattberry1]

Nice video thanks. Was there a mistake in the schematic though? I think it shows pin 6 to pin 2 via a resistor, but the circuit is pin 2 to pin 6 and a resistor from pin 6 to pin 3?

[@billiamyoho7866]

Ty good.

[@matthewflynn8513]

What is the best way to hook this circuit up to a speaker?

[@vaibhavbhasin3861]

@learnelectronics Electrolytic capacitor changes whole output wave, why? Isn't the Polar capacitor not suitable for oscillating wave? How is it able to work after changing cap?

[@mohammadrezamajidimosleh7917]

First of all, the waveform is changed in shape, because the scope is AC coupled and the fundamental frequency of the oscillation is so low, that the DC block cap in the scope has plenty of time to charge and discharge, that is why you see the steady voltage of square wave as an exponentially decayed voltage in the scope (First order RC circuit). For your second question, generally yes, but there will be no negative voltage across the timing capacitor in this circuit, so you can also use polar caps like electrolytic capacitors without any issue. The waveform that you saw on the scope screen is the output waveform (square wave) which is different from the timing capacitor waveform (exponentially charge and discharge). Moreover, negative voltage on the scope screen appears because the input is AC coupled so it removes the dc component of the oscillating wave on the screen. Changing the timing capacitor affects the charge and discharge time, which consecutively alters the frequency of oscillation. So does the resistor. As you increase resistor or capacitor value, the charge and discharge time increases, thus reducing the frequency.

[@Linguae_Music]

Thank you friendo

[@andrewburke6158]

would this not be a ICO? changing the resistance changes the output current and the tone. It does not vary the voltage much.

[@Sarahbuildsstepsequencers]

Would you consider showing how to do sound circuits for euro rack modular beginners? Like oscillators, filters, reverb, echo, envelopes, etc.?

[@learnelectronics]

I have been trying to build an envelope generator.

[@Sarahbuildsstepsequencers]

learnelectronics sounds good. And I understand about getting to projects. Caring for health should come first, imho. 🙂

[@gauravsharma5601]

Can you do a VCO for using LM741 in higher frequency range? Thanks

[@farvezfarook3422]

the control voltage vs frequency for this circuit is not linear but exponential

[@arcadebuilder533]

Need a stable (including temp stable) occilater for a reference signal... Need to set a frequency and know it's consistent for tone filter device i/o control...

[@fabriziobandiera1556]

Hi thank You for Your tutorials! For his schematic is there any chance to add an exponential converter ? Thank You in advance !

[@odissey2]

The voltage dependency of this VCO is highly nonlinear (~1/V), so it is not very useful for audio synth.

[@GerardWassink]

I also built this circuit. I get nasty peaks at the rising edge of the square wave, so that the Vpp = 21.4 Volt, PSU is set to 9 Volt. Any ideas?

[@mortenrobinson5421]

3:57 not obviously. It seems that many IC manufacturers can't quite agree where to put the vcc pin. I have another device here on my breadboard where vcc is on pin 1 and gnd is on pin 6.

[@gl0sek]

Your oscillator videos made me wonder about oscillators in switch mode psu's. As I understand first is bridge rectifier, mosfet and transformer. The oscillator controls the mosfet but at this point our voltage is rectified 110v/230v. So does oscillator work on high voltage or maybe there is voltage divider to lower the voltage for just the oscillator? Can we use 555 timer with switch mode transformer or do we need higher frequency?

[@mohammadrezamajidimosleh7917]

Main switch mode power supplies, as you mentioned, first generally rectify the main's sine wave to make it high voltage dc, and then using a (discrete or integrated) switch and a transformer, they produce the desired voltage (or current) at the output. In order to turn on and off a switch (for example a power MOSFET) you don't have to apply high voltage to control pin of the switch. Power MOSFETs in SMPSs typically need 10 to 15 volts at the gate. Although the control circuitry of a SMPS is not as simple as an oscillator, generally speaking, you can use 555 timer as PWM source for you SMPS.

[@mtalhakhalid1679]

These days experimenting with 555 ic using ioutput of 1 occilator and feed it as input of other and mix them

[@sgrimm7346]

You got pin 2 going to gnd on the schematic. It should have a cap in series before the grd connection....or am I missing something. The board is correct however.

[@diamony123]

What's the difference between this method and a pot across pin 8 and 7.

[@diamony123]

Would love to see you build some sort of frequency switch that works like addressable led strip...make an led turn on at a giving frequency...

[@learnelectronics]

Ill see what I can do.

[@diamony123]

​@@learnelectronics First of all I love your channel, great stuff. Here is my thoughts on figuring out addressable Leds. They say each Leds in a strip is turned on by different frequency. I have considered ideas like how a ir remote control works to spectrum frequency device. Its can also works like a vumeter in dot mode, where the chip on each Led converts frequency back to a set voltage to active the Leds. I think this is intriguing concept and would love to see just 3 leds perform this unknown trick using the 555 timer. I love analog and figuring how stuff works, Thanks

[@jasssam2502]

What is the extra wire connected to pin 3?

[@jtb8631]

So I found a circuit to control the frequency and duty cycle independent of each other, but to change the frequency a capacitor has to change. I am trying to build what I guess would be an arbitrary pulse generator(?), with independent duty cycle and frequency. And It would be nice to be able to control the frequency with a knob instead of the dip switch/capacitor array I currently have. Is there a way to do this with the 555? You have a ton of videos about the 555, so I figured you would be the right person to ask. Also you make great videos, keep it up. 👍

[@davecooper5951]

Could you do one on 'LFO's' - I'm currently trying to fault trace /improve a multi-effects guitar processor. Thanks

[@axelperez5166]

I have followed your instructions exactly as you outlined on the video. However, it does not work as you have indicated. I can't see how the how the cap you have on pin 2 would work. As you have it connected it would be invisible to the circuit. Please look at your schematic again. Thank you.

[@ludwigludwig3515]

1 Tl08, 1 resistor and 1 condensator makes the same. Integrating the output with a 2. Tl08 and giving on the 1. Tl08 makes a perfect 50/50 square wave.

[@michaelpadovani9566]

Long live the 555

[@khaledhosny9883]

Great, what is the value of the variable resistor and the capacitor voltage?

[@mu8502]

hey my friend I have a question: sometimes control voltage start from 8volt to 10volt(for example) but vco work with 0v to 3v(for example) volt what circuit can convert 8 to 0 and 9 to 1 10 to 3???????

[@kamleshchavan7451]

Sir any video on reverse engineering done on the RF transmitter and receiver of the RC control of any toy. How it is designed, how it works step by step

[@mixpixmixable]

duty ratio is also changed?

[@anthonyellis5517]

I’m pretty sure a vco has an exo converter?

[@TheJavaSync]

Hi Paul, I'm still confusing - if there is frequency or duty cyle if you turned pots - really sorry annoying You (I'm just hobbiest - pure electronics basics) - anyway loved Your videos so much

[@mythoughts9724]

How high can you take this oscillator?

[@larryyounger8674]

That variable resistor seems a little jumpy to me.

[@makingthings7682]

Can you please all the components

[@GiNodrog]

Looking at your diagram your timeing capacitor is shorted to ground !

[@prototype9000]

i like vcos that internally cook you

[@zonnig46]

I think "triple 5 timer" sounds better iso 5, 5, 5 timer.

[@1pcfred]

It ends just when the video was starting to get good. I expected something a bit more. Maybe a flashing LED, or a speaker? It is a 555 circuit after all.

[@1pcfred]

I know you're supposed to always leave them wanting more but this just seemed abbreviated to me. As if it is incomplete.

[@Ziplock9000]

Theres a million videos on YT for that

[@cybermascot]

do maths video as well please.

[@learnelectronics]

I will do that.

[@sayantanmaiti2513]

Please do the math in another video Sir..that will be useful

[@duality4y]

please get into the math i would love it

[@johnnygault365]

What is the average lifetime of an electrolytic cap ? Wondering how long this circuit would last or anything could be added to enhance its life Peace

[@aloysiusstone731]

Is Calculus absolutely necessary for electronics? Can the math for electronics be solved without calculus? I'm a noob to electronics and I can tell that algebra and trig is going to be helpful. I haven't seen anything yet that I can't figure out with Algebra and trig.

[@learnelectronics]

For early beginning work no. But calculus is the math of change over time. That becomes important as you get into calculating capacitors, amplifiers, etc... also we build integrating circuits

[@jaimegonzalez334]

El diagrama esta equivocado... gracias.

[@cheetahkid]

I just spot the mistake, on your schematic drawing you put pin 2 to ground.... errr yeah, bad one :)

[@dar0971]

Id love to get into the math

[@Neffers_UK]

Me too. Given the formulae it's not hard to sort out, provided you know the annotation and method, but what stumps me is having to keep values in my head as I slowly trudge through it. What you have just seen was just like Ohm's law, but with additional levels per value. I call it "ohm's law coleslaw" - it's dead simple to work it out (I'm lying to myself here) provided you can fill each value and keep track.

[@Eslar]

Where is the control voltage? Frequency is controlled by reistance and capacitance, so thats not an Voltage controlled Oscillator.

[@gokulsai901]

Replace the potentiometer by a regulated power supply where +v to pin5 and -v to ground...the basic idea of pot is to vary the voltage instead of using a variable voltage supply

[@gokulsai901]

XD been 6 months...hope that doesn't bother u that the reply is after 6 months

[@bryanbolton821]

Yes, do the math.

[@engjds]

Soon as you mentioned 555, I stopped the video, yeah it has a fan base, but so has the Commodore Amiga ).

[@Laediin]

Show me the Calculus!

[@learnelectronics]

Soon, young Jedi, very soon...

[@Laediin]

Do it while consuming adult beverages, so that you can...Drink and Derive...

[@lxm2600]

Might need to wait a while.. s in F(s) of a Laplace transform is definitely not ”seconds”

[@rayherriott6517]

The schematic is wrong - the 33K left end is connected to Vcc and ground - the capacitor 'C' has both ends connected to ground - ain't gonna work!

[@bblod4896]

I thought I saw a yellow jumper on pin seven.

[@learnelectronics]

Seven is nekkid

[@bblod4896]

Seven of Nine!

[@melplishka5978]

Please more math lol

[@Kenneth-mj1hk]

This video is so cursed lmao

[@learnelectronics]

makes me money

[@anthonyellis5517]

Is just not a oscillator?

[@PIXscotland]

Ooh... Furst... #IHatePeopleThatDoThat...

[@PauloConstantino167]

this is worthless

[@tobywan12]

VCXO????? Just VCO dude

[@easyelectronics4364]

Is it similar to pwm?