How to make a single transistor oscillator
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- เผยแพร่เมื่อ 22 มิ.ย. 2018
- How to make a single transistor oscillator
In this video we crate a single transistor oscillator by taking advantage of the reverse breakdown region of a 2n2222 transistor. You will need at least 12VDC and may have to try a few transistors before you find one that will oscillate.
Take note of the waveform, you get very fast rise times and and nice slow capacative decay.
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The reason that the led doesn't go all the way off is that capacitor is always charging through the led (or it is shorted through the transistor). If you want to flash, put the led in series with the transistor, and the capacitor across the transistor-led pair. Then the led will light when the transistor avalanches (discharging the capacitor through the led and the transistor. You can then use a larger charging resistor to get more reasonable time constants and slower flashing rates.
Thanks now I know how to fix that problem
Hmmm... I tried what you proposed with an LED, a similar NPN transistor used in the video, two 100 microfarad capacitors and 10k ohm resistor. I managed to get the LED to light up and then the brightness slowly diminished. It then didn't light up again though...
@@tanyongboon1082 This oscillator is using an undocumented characteristic of the transistor (the avalanche breakdown). Not all transistors will exhibit the effect, and some may require a different voltage. You might try increasing the resistor value. If the charge current is too high, then you maybe will fail to stay in the negative resistance part of the avalanche curve. So try a larger resistor first, and if that doesn't work, try it with a different transistor. I have even seen variation among transistors from the same batch as far as the avalanche characteristics, so if say on 3904 doesn't do it, the next one might.
@@argcargv I am observing a critically damped oscillation with one particular transistor. You are right. Only one of my transistors displays this characteristic. The others do not.
I just did a bunch of tests with this and realised that a very big difference is made by the colour of the LED. Red was like in the video barely fading but a green one was flashing. Try also different LEDs if you are having problems.
My love of analog electronics over digital is what made me become an RF engineer in a TV Lab. Love the work. And thanks for this video. We need kids to learn ana-elect much. Problem is, good teachers with good design experience is hard to come by.
Paul bringing back the finesse...
TBH, this is a very clever relaxation oscillator. Unfortunately, most of the simulation software is not capable of modeling a transistor in reverse avalanche mode.
OK, I'm going to build this circuit tomorrow. It's going to be about 100 and I'm staying in the airconditioned house. I read the comments and I'll try some of those ideas as well. Thanks for a teaser of a circuit and another good video!
I really like how this guy explains everything
Great video - thanks for posting!
Thanks for posting!
Just finished the circuit , could not see led pulse after adding second cap .Going to play with more caps later .Looking forward to next project thank you
What could we expect from playing with the floating base? Some frequency control maybe or wave form changes?
Do you have a schematic for this project? Didn't see one in this video as I did on some others.
I agree with the person that said about programming microcontrollers is too much of a go to. However, all of my projects always have a problem with " feature creep" and my background is programming, not electronics so I always graduate towards the microcontroller solution. It always ends up being bigger and more expensive with the discreet components now days than with the microcontroller anyway. In this case, you have 6 components instead of one. But I loved the video and the lesson, many thanks..it will prove useful.
It takes a much stronger mindset to design with electronics than to program, especially when the latter's pretty much about "library" calls on some compiler. A programmer is never even near the level of a proper electronics engineer, "big" components or not.
i only use analogue electronics,i actually have an arduino micro,but i never use it,nor any other real components...
i make capacitors out of paper and foil,instead of transistors i use magnetic amplifiers,also diy...
my only problem is that everything i make is kinda shitty and usually burns out or just straight up dies on me....
That true, but I love tinkering with analog.
good practical explanation of oscillator circuit, thanks
Is there's a simple way to modify that capacitor waveform to be closer to square waveform? IE, would a small resistor in series W the capacitor create a flatter peak?
Thanks for the vid from one STS to another. I hope all is well with you and if you are a ham I wish you 73s!
Thanks for the rapid reply
Np.
Very good doctor!
Thankyou very much for you time and effort has helped me alot
You are most welcome
Hi Paul, Love this stuff.
Is there any way to make a wave pattern that is like a triangle wave but the top and/or bottom of the wave moves horizontal like a square wave. So the wave is angle down, horizontal, angle up, horizontal.
Diode rectification can chop off the tops of the saws and make them flat.
Just run two diodes in parallel, in opposite orientations. Just a simple diode clipping circuit, and bring the levels back up with an op-amp, sparing a few details :P
Everyone loves diode clipping!
Use a 10k pot at the input to play around with the hz. Hook output up to speakers. Sweet.
Yep, gotta agree. I'm playing with one of those ckts right now and I have a 50k pot in place of R. I get all kinds of freqs. Good video. Anyone mention the negative resistance that's causing the transistor to short completely? I think it's called negative differential resistance, and it appears within a region in the transistor with the right voltage. Pretty cool.
How did you hook it up to speakers ? I added one end to ground and the other to after the transistor but the sounds is very quiet ?
@@yeah4768 Get an amplifier maybe to output on the speaker?
The capacitor is charging to a greater value than the battery is providing due to the load resistor. Changing the load resistor will allow the capacitor to charge to a greater potential than the battery can provide, and the depletion regions will become thinner and thicker with greater magnitude getting the transistor closer to on/off. I've been playing around with different oscillation schemes using 1 BJT, diode(which tuning the circuit is best an LED), and resistor. *I had not considered an open-base circuit though.*
The capacitor is manipulating minority/majority charge carriers, and thinning/thickening the depletion layer.
*With the right value resistor and a 12vdc supply, just about any transistor should pulse.*
My circuit has a 4.7K resistor to the emitter of a S9013, the capacitor goes from emitter to ground no limiter resistor on a white LED from collector to ground. S9013 flashes at lower voltages. Instead of the LED you can feed the base of a 2N2222 with emitter grounded then put a 12 Volt LED strip from +12 V to the collector of the 2N2222 now you have a "Chopper" circuit that gives nearly the same light but with less Watts since it pulses the current. At 12V both transistors can be 2N2222 I think.
Very interesting but it would be nice to know what values the resistors are please Paul thank you
Basically if you put a variable capacitor you can regulate the Speed?
Connect your cap to directly to neg. It will unload better and u will see a more positive oscillation. I also used no resistor on the neg side, slapped in a speaker to hear it.
i'm curious as to what it is about the specific transistor that makes it work/not work. maybe that battery operated component tester would indicate a difference between the one that works/doesn't work?
This weird function of transistors works with most npn bjts. But... Some transistors from the same batch won't oscillate. And if you use a different bjt, say a 3904 the voltage at which it oscillates may vary by up to a volt. Kerry Wong wrote a great article on this phenomenon.
lol I have a drone synth that uses this concept. Very cool. Thanks for posting. Would have been neat if you had also explained exactly why the transistor oscillates when used in this way but I'm sure there's plenty of videos that go into that.
There's not lol.
@@commentfailedtopost There is, it's called an Esaki oscillator.
There is, it's called an Esaki oscillator.
Hi very interesting ,what was the value of the two resistors you are using .I'm going to build one today.Great channel thank you
1k load resistor
330r led resistor
"We dont want that to happen... again" Hahaha made me laugh. Nice video thanks
The oscillator frequency dropped from 15hz to 10hz because you increased the capacitance from 200uf to 300uf, it would have dropped to 7.5hz if you had doubled the capacitance
You're right I went to 300 instead of 400. My mistake. Thank you.
I used old Russian Nixie tubes to make a 4 digit clock. No micro controllers pure old school logic circuits. I prefer my analog scope on my bench compared to my dsos. I love the sound and feel of the knobs. But I have to break out the dso when I have to do certain things that the old Tek can’t do. Like my tek is only 100MHz and both dso are 200 MHz with other goodies.
any tips on making vacuum tubes yourself? i know how to make mag amps,but i wanna make an audion so i can use it for a radio reciever...
@@danijelovskikanal7017 no I doubt it is possible. There’s a lot of equipment required to make tubes. They are manufactured similar to incandescent light bulbs so gotta pull vacuum and close the glass with a torch while keeping the vacuum in the tube also the inside bits the filament and the metal strips they are all made of very specific materials and the size of that stuff will determine how it functions. My best advice is to just find NOS (new old stock) vacuum tubes. You can usually find what you need there’s a lot of new tubes out in the wild. I have found Russia is the place to get them. They used vacuum tubes longer than we did. So there’s a bigger supply of them from there. Good luck buddy with your project. I’m curious what you are trying to do.
I would love to make a single transistor oscolliator with 5volts. Any ideas?
I believe I know what’s going on here. The LED is getting consistent voltage. The capacitor is discharging causing positive voltage peaks. Thus, is your sawtooth waveform.
Yep
Can you make a transistor (no opamp) circuit that fades an LED on and off?
When you said "wonder why that is, " that capacitor takes longer to discharge than it takes for the transistor to come back on I think - so it never completely shuts off although it pulses.
I believe i've saw something on hackaday and it makes saw like waveform related to the discharge of the capacitor. Try a 1.2M Ohm feedback between the base and colector :P
If you don't do the feedback leave the resistor floating on the base and then touch with the finger. Best used with two 100uF in parallel :D
You got the collector hooked up to the negative rail or am I mistaken?
Coupling capacitor at the output to kill the DC bias
can you show us how to make an analog ico?
I noticed that the setup, regardless of capacitor size, is extremely sensitive to voltage input. With my DC power supply set at 9v (same transistor, yellow LED), the LED didn't light up. An increase of .5v made a slow, visible oscillation that increased with voltage up to 11v, when the LED became visibly stable. Didn't measure with an oscilloscope
Now this is some fuckin finess
Cool. I want to build a syth with multiple oscillators
1. What kind of transistor is that? Can you put up a schematic? Great video. Was looking for this circuit. Thanks.
As he said 2n2222
hi so does mosfets constantly switch on and off on their own
At what frequency do they ?
Cap in parallel doubles voltage and decreases fared
Use a 1kohm resistance and 3300 uf capacitor. With a 12 to 15 volt power.
I made a relay oscillator frequency is inversely proportional to the capacitance.
how would i connect an audio output to this circuit?
I was pondering over what a practical application to all of this might be. This was the first place I clicked in beginning my quest to comprehend synth's..Key-word OSCILLATOR. What a hopelessly captivating 'field' of interest (as in FORCE FIELD).
A showing of the circuit diagram will be helpful.
Rookie question: Over the course of one or two cycles, what is happening in the capacitor?
Try placing the cap between the emmiter and ground...
What can a sawtooth oscillator be used for?
if you put it through a comparator you can get a pwm wave
audio synthesis
also connect capacitors in series
All right... one question. I saw in another video (which I can't quite find at the moment) that it will work with almost 100% of the transistors if you cut away the unused base leg. Simply bending it or leaving it unsoldered won't do. The maker of that video did show this trick but admitted he didn't know why it worked. Why that happens?
While I definitely dont have the absolute concrete answer. I would guess that the leg acts as an antenna. And being free floating, it can go high or low. If it floats low it will close the C-E channel.
Can you put a 3.5mm audio jack on this?
Sure
@@learnelectronics Do you mind if i ask how? My experience in audio cables, jacks and wiring is about as good as none
What is the need of the floating base? What does it do actually? And what if I touch it?
Build the circuit and see for yourself.
There isn't an actual need for the base.
At all.
We're using the transistor as a diode. This is called the Esaki effect, and the older component of this is called a Tunnel Diode.
They don't really make tunnel diodes like this any more. The TVS diode is not an equivalent.
Tunnel diodes were extensively used in the 1960's but have since fallen out of favor since transistors, such as the P 22222 can be used instead.
The transistors are thought to be more versatile in the applications that they can be used in, but they aren't as rugged.
From the perspective of the electronics manufacturer, the diodes represented stock that didn't move very fast, so they were phased out. This is actually to the detriment of the consumer, who would be better served with a tunnel diode in the same application because it weathers better (in every way i am aware of anyway....).
Touching the base messes with the junction capacitance, which could be detrimental to the circuit, but i'm not inclined to test pulsing voltages.
Touching it distorts the output waveform .... it's awesome! 😆I bend mine all the way up like an antennae.
@@learnelectronics Why not use an RC circuit to switch the transistor on and off driving an led or load?
Putting capacitors in parallel only doubles the capacitance if both capacitors are equal value. Add the capacitors together to get the overall capacitance. Capacitors in series decreases the overall value.
🏆
Thanks, I like implementing analog circuits in discrete device. English is not my native language. Am gassy.
@learnelectronics your video description says "You help is appreciated"
It is.
Wait, how did you know it was Saturday?
i dont know about you guys but that would sound good as a synth and a LFO
If you want an observable blinking make it wave at 1 or 2 hertz
Might try to put the LED between the transistor and ground.
I need circuit diagram
Can you show how to get 60hz ?
you are breathing very hardly, i hope you r okay
lol right, with that and him basically having the mic INSIDE his mouth (sounded to be anyway) it was soooo distracting and for some reason made me upset.. my first id of his that i have watched so idk if this is a single incident of regular, but i'd think, or hope, that by this many subs that he would have figured out his audio setup haha...
@@josephdragojevich7041 He has Congestive Heart Failure. So you might want to delete your stupid comment! He is a great guy with health issues. Yet he still helps people learn.
He always has a positive attitude and makes it fun to learn new things.
@@mikelee1906 ok and your point is? you're the one who needs to chill out bud, i know plenty of people who are far sicker thean you claim him to be and they dont swallow their mic.. i wasnt saying ANYTHING about how hard he was breathing nor was i calling him any names, ALL i said was to get the mic out of his mouth THATS IT! its people like you who would drive off potential subs to his videos just because of how fast you jump down someones throat, and THAT is something NO ONE needs here or anywhere so how about YOU gtfo.. Cheers! :)
@@josephdragojevich7041 That is your takeaway? You are hopeless. You are really going to double down with that loser stance. "it was soooo distracting and for some reason made me upset."......and I need to chill? Sure thing snowflake! Karma is going have fun with you!!
@@mikelee1906 :) oh yeah IM the snowflake lol, you are the one who started crying to start with. thats ok i understand you have to do your virtue signaling so you dont feel worthless its ok, the rest of us actually mean something to the world and add to it.
6:21 🤣
I've tried multiple transistors, capacitors, voltages (9 to 12), but I can't get no oscillation! Anyone knows why?
Fosco Lucarelli Might need a little higher voltage, depends on the transistor.
Sawteeth wave
Pnp or npn transistor?
npn
I didn't see the LED flashing
If you get capacitor off the led was on.
🤗🤗
use a white led
i dont understand why using transister can any one explain even the base is set to 0 how!!
Something to do with the capacitor charging up until it reaches the breakdown voltage of the transistor, and then the capacitor discharges through the transistor, flashing the LED. The base isn't needed, because you're simply "overpowering" the transistor as a diode.
@@pavansaikumarreddy4859 Right, reverse biased. But I still don't get why the capacitor discharges.
you can't hate technology simply because it is not using what you've learned your entire life, microcontrollers allow for much more advanced systems, we cannot sit around in the 60s bcz it shows how educated you are in building circuits
I thought it was dangerous to touch the two wires of a capacitor if it hasn’t been discharged?
You can be shocked
Large ones yes, that cap is relatively small and can't store a dangerous amount of charge
yea i agree and i am so tired of hearing about arduino.
Where the schematic circuit ?
It's called an Esaki oscillator...
Esaky Oscillator.
how is this dude out of breath after saying 1 word
Probably from the congestive heart failure
It is a very very very bad circuit because it broke transistor
It's just a trick, and only works with some transistors.
@@learnelectronics its only working with bad transistors and it damages my. Its not bad meant but please show you the circuit with 2 Transistors that doesnt damage transistors and works forever
@@boxritter this circuit has some popularity for audio synthesis. i see lots of documents about it. this is the first mention i have seen that if you build it, it won't last for long, which seems sensible considering the method. but, i think we all know that it will take years for your method to become as well known.
eg. "string machines" which use say six saw oscillators slightly detuned would be inexpensive to build.. add a resonant filter, you have a classic synth voice.
But can it play megalovania?
I burned transistor with this kind of circuit. Transistors should not be used in this way.
Its a trick, not a useful circuit.
اسیلاتورش بنده اینومن نمیگم
umffff
Transistors are not intended for such applications. My question would be: how long would the transistor stay alive until it breaks down?
I think that transistor was damaged because the led didn't go off.
bro your breathing sound makes it very noisy
put eye on it for next time
Bro could not bright 🤔