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- เผยแพร่เมื่อ 11 มิ.ย. 2024
- Easy relaxation oscillator. All you need is three components, plus the power source. Works as LED flasher, tone generator, or AM modulator. Very good web page that goes into detail about this circuit -----
www.cappels.org/dproj/simplest...
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Wow, 10 years ago....now april 2024! Thanks man! I'm i glad this post is still around. I was wondering about a simple occilator 😊. Also thanks to TH-cam ! 🍀 FM.
Thanks for the like ! It made me look again to the video! We are so spoiled with TH-cam, bombarded with one post after the other that we easely forgets yesterday's post. Electronics stay's an other univers to learn about, for me. In this case i wanted to compare in a simple way my "EARRRINGING" sound with an electronic fabricated sound. Knowing just a little of electronics, ha 🙃 ! This post helps understanding. 👍. Thanks, 👋🍀🌞FM
All Silicon BJT's Base/Emitter junction have a forward bias voltage of around 0.6V but they also have a 6 - 10 V reverse bias breakdown voltage point. The Base/Emitter junction is effectively a Zener Diode, the Base/Collector though is just a normal Diode.
Having said that, the way this circuit functions is .... As the voltage rises on the Cap due to the current coming through the Resistor eventually the Base/Emitter junction will perform like a Zener and with the forward Bias of the Base Collector junction, start to conduct, this will effectively discharge the cap but not before the LED has lit for a short while using the current from the cap. The cap will then start to charge again as the Base/Emitter junction would not have enough voltage across it to maintain conductivity. This would also explain the LED being on then a sudden brightness before the LED goes out, the 'Zener' would start to conduct a little before it goes into avalanche allowing the LED to light then when it does avalanche, the current goes up quickly making the LED bright and this discharges the cap turning the LED off. The process repeats
But why is the transistor not in avalanche from the start due to the power source?
This is a great video because when I was in college, the engineering club cleaned out their office or club house and me and my friend suddenly found our selves the owners of all this old technology but it was/is still functional and one of the components were these gold capped transistor and I think its those Texas Instruments Transistor you were using. So thanks again Erik, I think I dig those transistors up and see if I can use them.
great video, made me miss undergrad... had a big smile on my face when your single-transistor AM voice transmission succeeded
Wow! I actually understood that. You explain things well and I'm finally getting to grips with basic electronics. Thank you.
Thanks, this is a great video with fantastic explanations for a total newbie. No impenetrable abbreviations, and you go an extra 2 beyond each concept to give a good background understanding.
Nice video. And I like your lab.
Now, you correctly called it a relaxation oscillator, but say that it uses the "negative resistance" of the NPN. I have two comments on this:
1) True, it has a negative resistance region. But the circuit operation is not based on this negative resistance. It is more correct to say that it uses the "snap back" effect that is associated with secondary breakdown. In other words, the NPN is used as a self-commutating switch, not as a negative resistance.
2) For the record, relaxation oscillators and negative resistance oscillators are two different circuit categories, and they work very differently. A negative resistance oscillator would keep the NPN biased in the negative resistance region continuously, as opposed to letting the NPN switch on and off. Also, a negative resistance oscillator requires a resonator, such as a crystal or a tank, and can't be made with just an RC.
I love this, good explanation and examples, I wish there was more people like him on youtube
Thank you for posting a simple understandable explanation of this circuit. Very cool.
00:27: Dear High Voltage Hot Dog: That is a Texas Instruments TI-30 scientific calculator? Wow! My parents bought me one in the 1970s when I was in high school!
I just modified this circuit and used for part of a school project, thanks a lot!
Came from Hack A Day. I have a bag of 1970 TI SWC1035. Now I know why there is no info online. Nice video, thanks for sharing.
Very Elegant Indeed !
Perfect for my application.
Thank you.
wow this takes me back a few decades. reminds me a little of a oscillator that used a rc network and a programable unijunction transitor.
Excellent! Thanks for the video.
Just tried it on the BC547 B as well. I didn't even need to adjust the voltage. Just swapped it over for the N2222A. Cool.
Thanks for the info. I knew this was not a new discovery and I was sure there had to be some website that describes it in detail.
COOOOLLLL1!!!!!! THANKS FOR SHARING :) you get junction breakdown of the emitter base which is about 6 - 8 V
Very cool, I just tried this out and tried all different caps.
So simple and nifty, I'll have to give it a try, misusing a transistor, very interesting. Thanks..
Penn State Salvage Yard - State College - Yes! Very good presentation, very good use of out dated equipment. Fantastic actually. A case study should be called for.
Thank you.
Awesome circuit, thanks for sharing.
The frequency is strongly affected by current injected into the base - if you use a low frequency and lower the input voltage close to threshold you can 'measure' ac fields by touching the base with a finger and putting your other hand close to a source (mains powered equipment or what have you). You can even get a theremin-like effect where the frequency depends on where your hand is. Great fun!
Well done! I learned a bunch, cheers!
Interesting Video. I had an old AM Radio just like that when I was in the Army the 1st time back n the late 70's at Ft. Hood,Tx. I loved that Radio until someone broke it for me.
Thanks a lot for sharing your video, it's very interesting. I agree with you about what they teach in electronic books where they show the basics and in doing so they use some circuits that I think are not the best options for electronic applications or practices, and meanwhile students miss the opportunity to learn about other principles that could be more useful. I made a brief view of your channel and you have very interesting material that I'll check later, so I've subscribed. I liked your LED Lemmings' circuit, it's fun, hehehe. Regards from Panama. :o)
Good job , thats what i was looking for
A very interesting effect. It brings me to the idea to try something similar with a Zener-Diode. I think, that should also work.
Zener diodes don't avalanche.
The required voltage depends on the transistor used. Some need more voltage than others. I do not know of any transistors that can go into negative resistance at lower voltages.
Nice bench! Hang on to that 576 curve tracer. Last I looked they were still going for about $1500 each on ebay. Have used - and repaired - a lot of them but never could afford my own. (Actual 576 I mean, have built many discrete curve tracer circuits over the years but haven't owned a factory built!)
I think I have learned that in the university, when we have played with the curve tracer, we had box of parts to try and we had some transistors that did that. And we had that explained to us. One of the few interesting things I had, for some reason I was not in EE but in mechatronics... almost everything was mechanical engineering though...
Great job man, thanks.
Great video and easy to do its a must to try...
Very interesting - gotta go check it out myself :-) - Thanks
Nice find. Thank you for the info.. Love the curve tracer. I have not seen one since College.
Simply excellent!
very interesting congratulations
Pretty cool... Just made this circuit and it works well!!!
I just made one, exact. didn't work.
The schematic at 5:45 says 12-18 volts; were you using a power source in that range? I tried it with 9V first just because that was more conveniently accessible and the LED didn't light up at all, but then I tried with a 12V A23 battery and sure enough I got quick flashes of the LED at a regular rate.
Seems you can make a nice voltage controlled oscillator for PLL work for medium and short-wave.
This led to the diac, the UJT, and the PUT. People use this in noise generators and square edge sharpeners.
Love all that Oldskool advanced lab equipment! How did you aquire that? Especially the curve tracer, that must have costed a fortune back in the day.
.......thx, from comments I see the effect is avalanche breakdown and I've always thought this should work with zeners but never tried. The turn off voltage needs to be conveniently lower level than turn on voltage to be useful and I assumed zeners didn't have this convenient range but I'm too lazy to try it.
Real negative resistance is of course with tunnel diodes which operate at less than a volt. Clive Sinclair came up with some interesting circuits in 1960s for tunnel diodes , I'm positive he must also have been a real Q for mi5 . I never had any luck getting tunnel diode circuits to work , I now think that maybe they were faulty diodes , I have some vague memory of plotting the a chart for one and seeing it confirmed to published specs or that might be a dream but anyway in mid seventies our own Electronics Australia magazine had a two page article for connecting up p junction and n junction FETs to act as a tunnel diode and wire up with a coil and capacitor to make a sine wave oscillator and that circuit worked immediately and produced a very clean sinewave judging from the sound in a speaker. I gotta find some old magazines one day to dig up that circuit again and maybe put heaps of other circuits too on u toob cos the staff had stated in the letters/correspondence pages many times that they made no claims to intellectual property for their circuits , copyright for the written accompanying article may be a different matter though . EA was perhaps the best electronics magazine in the English speaking world and commenced in early 1920s and closed in 1999 with Silicon Chip magazine then inheriting their copywright .
Great video thanks.
The BC182 seems to work well too!
Thanks a ton Eric. I have just started out with electronics as a hobby and this was a great introduction to the practical use of the reverse bias property of this transistor. However I made this circuit and face a peculiar problem that I am not being able to figure out. As I understand it, the LED glows when the capacitor is charged and releases its charge through the circuit, causing the transistor to be in a closed switch state. When I use a red LED in the circuit it works. But if I use any other colour the LED slowly lights up as before and remains lit. Bizarre!! I for the life of me can't figure out why. I am using a 1000MF capacitor and a 2N3904. Earlier I tried a PN2222 and that had the same effect as in the LED would remain on and not produce a pulse no matter which LED I used. The circuit started working when I replaced it with a 2N3904. Can you please please explain what is happening? Why is only the red LED producing a pulse? Something to do with the resistance of the LED itself?My input voltage is 12V.
+Kunal Verma Different color LED have different Vf voltages (voltage where they light up) and different current draw. For this circuit to work, the LED needs to draw the cap charge down fast enough to turn off transistor. Try lowering the supply voltage or increasing the resistor. All must be in balance for oscillation to occur.
It's very interesting!
Is it useful to build a multiwave oscillator for an analog synth.? So I guess it can give square and triangle waveforms with some additions? The most important - is it easy to remove DC offset? Or the whole schematic will be much more complicated than OpAmp based oscillators?
Good small Oscillator , even it low frequency but it will have a lot of application for it .
Very ecelent done, like your other videos ! I like it.
Question:
Did you try how much voltage you need to break the emitter barirer?.
Try short dirac pulses, and then later normal voltage ramps up curves.
Greetings form Holger.
Thanks for showing your Books, that was great.
Thank you. On the curve tracer, the emitter breaks down at about 8 V.
Great video. Does the supplier have any more of those transistors? They are ideal for strange experiments. Thank you very much for sharing.
Thank you for good explanation of this circuit and for recommending good book about electronics. Can you recommend other books about electronics?
Cool could this work with a lower voltage source? Thanks anyway I appreciate your feedback
Could I also pump the voltage using the cap at the same time?
Say I had 130v incoming smooth DC, and a cap that could take over 100v (with a blocking diode to prevent it discharging back) and assuming my BJT (or zener diode perhaps?) had a breakdown voltage of around 200v, wouldn't that give me a 200v peak wave?
I'm thinking it could drive an electroluminescent display.
I really love your video , thank you very much , I want to learn to make my own eurorack modules , how can I learn this?
Very interesting.
just tested works great.
thanks for sharing!
Thanks. I have no idea where the transistors came from. I just happen to have them at work.
I like the neon oscillator with so many 9V batteries! Nice! How long do you think it will last?
Dude...!!!
thank you so very much...
Works with some types of caps, with others doesn't and frequency is very unstable. But a had fun experimenting.
I have read that it often takes a few tries/a few NPN's to work. If it does not work does it ruin your NPN or is it still good to use it for something else?
hello Eric sir,i have one confusion in your relaxation circuit schematic you did not bias the base-emitter junction,base terminal is left unconnected then how does transistor let flow the current in LED,please clarify
Hi - I'd like to know how high you've tried to get the frequency for this circuit. I'm looking to prototype a 80kHz sawtooth, and this is going to be my first attempt before the common things like opamps.
Also, possibly worth sharing that most SPICE simulations won't simulate this circuit
I haven't tried for a maximum frequency, but in the AM transmitter circuit, it's going at about 700 MHz. 80 kHz would be no problem.
Will this oscillation occur if we forward bias the transistor?
Just curious, where did you manage to get those? We're they from some electronics surplus place or something?
Are going to return to making videos sometime soon? I like your subjects
great discovery
Eric Wasatonic ,
hey i also have some bjts however they are the 2N6427-4, and 2N4401-5 BJT's and i have two types of power transistors coming. they are TIP36C + TIP35C , and TIP42C power transistors. do you think they will work in the this circuit? i have a 9V battery source and a 11.1V , 5.5Ah lithium cell to power them with. i have several kinds of resistor mainly .25W ones and out of the more powerful ones i have 1Kohm and a bunch of potentiometers from 5-250Kohm. my capacitors are 1000uf, 3300uf, 2200 uf, and 1uf. i think this should work easily, as i want to hook up a large load to the circuit so i can power a variable frequency electromagnetic experiment. also i seek to make a inverter from as little parts as possible so i dont need to buy one and at a size that it can fit in my hand and this seems like the one that can do that if i install a transformer in its output.
thanks
The oscillator also works with the 2N3904
I have a question about the simple AM transmitter you built with this circuit, and am posting here because the comments were disabled on the transmitter video.
How did you design the antenna and can you post a link for how it works? I am an amateur radio operator and experimenter and for the life of me all I can find online are tutorials on dipoles and vertical whips, but the antenna you built did not look to be either.
73 KD9AQR
Matt Rienzo I just checked out the AM transmitter video, and comments seem to be working fine. I designed the antenna based on pictures of VERY early radio equipment the 1920's and prior. It is an AM loop antenna, and it works by picking up (or transmitting) the magnetic portion of EM radiation. For the one that I built, I had no design plans. I just made the frame from two paint stirring sticks, wrapped 10 turns of 22 AWG, and hoped for the best.
Just for info, while the circuit works fine on a breadboard, apparently the SPICE models don't account for the Avalanche breakdown. Multisim 2012 (using both transistors) failed to simulate it. By the way, I also like your lab!
hi sir ,i want to oscillate dc with high frequency so that output should drive a transformer.so, will your circuit be helpful in that condition?ican i take output from the place where the led is connected ?to drive transformer.please help
it is a simple generator when you look to the amount of external components, however it can be a lot more simple and understandable still. sadly the internet escalates everything to balance into one single point and so you won´t easily find the other peaks. however in short, this cirquit is a waste of transistors, because you do not need to use the transistor. a single diode can replace that transistor which also makes the cirquit a lot more reliable because diodes are rated for such things, while transistors are tested and tuned for completely different things.
so that might be a even more interesting project for you, because that would make a even simpler and a lot cheaper oscillator. also it will probably seem like magic to all of those who havn´t read a datasheet. some diodes will be more difficult than others, and some might make it near impossible because manny diodes will get a lower voltage drop on lower voltages. for example I found that a uv led would go down to around one third of it's rated voltage drop when the voltage went from high to low before it would practically stop conducting, it would start conducting when it came around 2/4th of it's rated voltage drop before it would start conducting again. I used a uv led because it was that or a high voltage diode, I used it in a switch to detect voltages higher than a certain point, but you could make it a frequency generator as well. and ofcource if you have very low voltage diodes you can (better for generating signals) connect them backwards, that is the thing you do with these transistors and it will give a sharper edge and thus make it more simple to generate a signal.
Do you think it would flash fast enough to make a TV flyback create a spark?? I like dong things just like you do...there is no limit right?:???
It's a grt invention
This is fascinating! Do you know anyway that I could incorporate this behavior into a transistor's SPICE model? I was trying to simulate this behavior on Multisim 13.0 without success. The simulated backward biased unhooked-base is simple leakage behavior with this marvelous affect totally missing.
I too tried to simulate in multisim , if anyone is successful please help
love your calculator
Thanks. My old LED calculators have cameo appearances in several of my videos.
Eric Wasatonic
Yeah, I have HP-41 CX
Where did you get that curve tracer ?
this may have already been answered in the comments but is the resistor in the schematic a 250 or 750 ohm?
How that transistor working without base connection????
Okay, after watching Full video i understand the concept
Excellent circuit. Simple and elegant. I was toying with a similar idea in my head but was using zener diode instead of the transistor. The reasoning was that once the capacitor voltage increases above the zener voltage, it would conduct and drain the capacitor charge. Then the capacitor would charge again and the cycle would repeat. But it does not work that way but rather settles at a steady state where the cap charges upto the zener breakdown voltage (I think somebody in the comments already pointed this out and you said the same thing).
So, it is the negative resistance which does the trick. Here, when the voltage tries to decrease, the current increases thus giving a chance for the capacitor to drain charge.
But, I still have a question. We traditionally study that for all oscillators, an amplifier and feedback is required. Also, something called a Barkhausen criterion needs to be satisfied. Do these really apply to this circuit? Maybe the amplifier and feedback are implicit?
I believe the negative resistance provides positive feedback.The equation for simple harmonic oscillation has solutions of the form exp(At)*sin(Bt) which is a sinusoid with an amplitude that is an exponential function. Normally A would have dimensions of R/L or some other combination of variables which includes resistance and produces a constant with dimensions of 1/t. Usually this "A" would be negative in sign which indicates a decaying sinusoid but with negative resistance it is instead being reinforced. An active component supplies the negative resistance which introduces more energy from the supply into the oscillating system cycle after cycle at the natural frequency until a maximum is reached.
Thanks!!
Could you use a Zener diode there?
excelente!!!!
Can i use bc548 or 2n3055 transistor
You can see same when transistor is connect properly at higher voltage. Avalanche effect appear in collector base junction too. Just apply 1,5 to 2 time higher voltage that is in datasheet. For 2N2222 effect will appear between 100 to 200 volts. Just make sure that resistor is 100k or more.
Otherwise transistor will be damaged.
Can you create a synth oscillator with this?
What are some uses for this? I made the circuit successfully and was wondering if the output could be fed into a step up transformer for higher AC voltage?
Donald Eslinger It's more of an educational tool than a truly useful circuit. A small transformer should be able to step up the voltage, but it might also interfere with the circuit's self-oscillation. Give it a try.
Eric Wasatonic Okay great. The input of a small transformer would be where the LED connects right? I would connect that to the primary winding or whatever configuration I wanted to try.
Donald Eslinger Yes, it would be good to put the transformer's low-voltage coil in place of the LED, in series with the transistor. A laminated iron core power transformer would work, but you'd probably get better results by using a ferrite core transformer, like that typically used in Joule Thief circuits.
How can I use a cristal of quatz in this circuit?
Have the rules of electronics changed or smth? I just can't get this to work...
Hi Eric,
Good job !
Just tryed the flashing led circuit with 2N3904 and 2N2222A, but unfortunatelly, it didn't works.
By simulating the tunnel effect by rapid short circuit between Emmitter and Collector it's ok, but with the transistor alone, no tunnel effect.
I made a circuit using this technique for the drop end charge for a solar charge controller, but again no tunnel effect. What is the secret ?
It will work with almost any capacitor. Smaller cap gives higher frequency. But it will not work with any resistance. Resistance cannot be too high or low. It takes some time to try different values to get it right. It also requires relatively high voltage, at least 12 V. Better to start with 18 V from two 9-V batteries.
If you have the transistor reversed at low supply voltages it will still amplify, just poorly. This then is using the reverse leakage to turn on the junction like a regular device, though long term it will degrade the junction.
i dont get it , powering the middle of the transistor?
Please what is the name of the book
i found out how to make it with standart BC547 NPN tansistor! just add a rezistor betven emitter and base! easy! (that resistor also sets the frequency)
Wow, thats smart
I have a magnifying glass with a 3v supplied incandescent bulb that I'd like to convert to a white led, if I used your circuit with a voltage multiplier circuit, would it be worth it?
Or would a joule thief be easier?
bridgendesar Definitely go with a joule thief.
just use a resistor
now that's something cool!!
I ask could use it as Oscillator multiplier .
What maximum frequency output?
I did this with 2N2222 and LED is flashing ok, but I can't hear sound when speaker is connected
Connect the unused base lead of the transistor to an op amp(outputted to a speaker) and you will get tone!!!