Working principle of multivibrators
ฝัง
- เผยแพร่เมื่อ 10 ก.ย. 2024
- Content:
00:17 Transistor switching another transistor
01:30 Bistable multivibrator (flip-flop)
06:04 Monostable multivibrator
14:22 Turn-on time
15:31 Astable multivibrator
19:04 Distortions of the output signal
19:54 Astable multivibrator with op-amp
More about multivibrators at the project page:
www.homofaciens...
Thankyou for the info Arnold swarzeneger... Astalavista
Don't kid me - you might get terminated...
The way you connected the elements just like in a circuit diagram! Awesome!!
Tanks!
My intention is not to get many views, but views from people who are interested in the stuff I am treating at my videos.
So if you like the video, talk about it to those friends who are also interested in electronics.
You're welcome!
...several days passed by until my ideas were recorded, edited, drawn, cut and finally encoded.
That is the first circuit that i have built as a child that worked I was so happy
Yes, the first blinking LED circuit was also an experience that changed my life (somehow).
MY MIND IS BLOWN...Thank you for this informative video.
+SelfGlassImage You're welcome!
Thank you so much for such a great video with clear apparatus which provide me a clear Insight of what's happening and omit all the misconceptions described in other channels..
You're welcome!
I have a number of those cheap op-amps in my electronics reservoir. They are not "state of the art", but are suitable for demonstration purposes, as it is easy to go to the limits of those devices (you don't need a high quality oscilloscope to plot the limit frequency or maximum slew rate).
Excellent video! Very clear and thorough. Well done!
you are the best teacher i know..... great.
Great video. Good way of showing circuits. Shame wont get high views because people are dumb. Thanks
thank you very much that's the circuit I was looking for.
Great explanation, a thumbs way up and a definite Subscribe!!!
Very good videos! I am planning to use a bistable multivibrator and a HCZ-H8-A humidity sensor for a spinkler system. The water should automatically flow to the flower when the resistance of the sensor goes high and pass certain threshold. That means that the soil is not wet anymore.
Thanks!
I guess you won't need an astable multivibrator, but a Schmitt trigger:
Operational amplifiers
HomoFaciens
Yes, thanks. I will change slightly one of my photo relay schematics, but instead of photo transistor i will use a humidity sensor. The threshold when the water will be flowing will be adjusted by a pot.
Thank you very much , so accurate and very professional explanation ...
+hagop vittali You're welcome!
The off time of T2 belongs to the charing time of C2, starting with 0V, So the off time becomes independent from the time the button is pushed (the capacitance of C2 should be low, hence is gets charged quickly).
C1 starts with +9.5V from the right to the left plate. When T2 is turned off by the button, T1 is turned on via R3, connecting the left plate of C1 to (nearly) ground, hence the potential from the left to the right plate is -9.5V and the right plate of C1 is connected to the base of T2.
Thanks!
The resistance values at the bistable circuit are not critical. The current running through the base of each transistor must be sufficient to bring the device into saturation or at least close to it (have a look at the datasheet). I have chosen 12k for the series resistors at the base pins and 560Ohm for those at the collector pins (the current through the LEDs is also running through those devices). 1k resistors are switched in series to the LEDs. The transistors are type BD175.
At 2:50 the left transistor is turned on and the left LED is therefore turned off. There would be a voltage drop of about 0.2V across the collector emitter junction of the left transistor. Therefore even when the LED is off, there is 0.2 V being placed across the LED correct? I realize that is not enough to cause it to be forward biased and hence light up, but is there a way to design the circuit so that no voltage is being applied to the LED when it is supposed to be turned off?
Yes, you understood the working principle.
Absolutely no voltage will be impossible in a real circuit. Whenever a current flows through a device, it causes a voltage drop. You can reduce that voltage to a minimum by choosing transistors with a very low on resistance and by optimizing the resistance values to get as close as possible to 0V.
Designing a flip-flop using operational amplifiers will bring you closer to your ideal circuit.
very clear explanation, I really liked it
Great presentation. One remark - the electrons flow from (-) to (+), even if it's assumed the abstract "current" flows in the reverse direction.
Thanks!
You are right - the electrons are indeed flowing into the opposite direction of the "conventional current" defined to be a flow of positive charges. I choose to use the "referent current" running to ground. I hope that I did not mix the two definitions of current in the video, or did I?
Sehr herrlich und spass! Educational and the same time fun video!
+MrCrazyDuck47 ...den Spass gibt's auch auf Deutsch:
th-cam.com/video/NsQKqehnVWk/w-d-xo.html
thanku very much... i got very clarity by seeing thus videos
+reshma ch You're welcome!
There is nothing wrong - yes, the upper plate of C2 gets charged to -9.5V, as soon as T1 is turned on completely, because C2 is switched in parallel to the base of T2 as long as the button is pressed. And yes, the time is dictated by the time required to charge C1 via R2. The capacitance of C2 is clearly lower than those of C1, to there is almost no affect while C2 gets charged to -9.5V by C1. I have added an oscilloscope plot at the project page to visualize the procedure.
Nice job, very well explained.
Very good.
Thanks
I'm a little confused, because the diagram I got, doesn't say to add a R between LED cathode and ground. Do you use a NPN transistor or a bi directional one? Maybe it's that thing I did over see? I'm talking about the astable MV of course.
What time index in the video do you refer to?
this video is really awesome! thank you!
I am testing the schematic on 15:45 with different capacitances. Can you tell me wWhat exactly is happening when i put 47uF on the left side and 20uF on the right side. One of the transistor is ON much more time, because the capacitance is more than two times bigger, but why exactly?
The lower the capacitance, the less charge has to be accumulated to get a fixed voltage level accross a capacitor. The voltage accross the RC circuit with the lower capacitance is increasing faster. The right capacitor is affecting the base voltage of the left transistor, hence the base voltage is reaching the 0.6V level more early, the lower the capacitance. Thus the left transistor is turned "off" for a smaller period. Since the LED is lighted up as long as the transistor is turned "off", the left LED is flashing shorter than the right one.
HomoFaciens
Thanks a lot for the good answer, it helped me a lot! : )
Have a look at the video description. There you can find a link to the section about multivibrators at the project page.
How would i know which values to use for R1, R2, R3 and R4 as well as what capacitor?? Im having trouble figuring that out for setting the LED on a specific amount of time of ON and OFF. thanks pls reply :(
Did you have a look at the project page I mention a couple of times in the video?
homofaciens.de/technics-base-circuits-multivibrator_en.htm
Great video!
Referring to the Monostable Multivibrator when you introduce the new capacitor C2 (12:20): Who determines the duration of the off-time for T2 in the two cases of button pressed and released quickly and button pressed for a long time? (are the times equivalent?)
Can you tell me if this is correct:
Just before the switch is pressed, C2 has a charge of 0V and C1 starts with a charge of 9.5V.
Then what happens when the switch is pressed? Will C1 force -9.5V on the right plate?
Thanks
thank you for good explanation
Does the electrolyte capacitor does not get damaged due to the changed polarity? I have learnded that those capacitors are polarity sensitive.
+Yoram Stein A reverse polarity of just 0.7V doesn't cause damage. If you go above 1.0V, electrolysis will happen that destroys electrolyte capacitors.
In the first circuit, the LEDs are connected via Transistor Collector - LED - Resistor - 5V . On the second circuit, it's done through Transistor Collector - LED - Resistor - 0V. Why is that ? Is that just to align the push buttons with the LEDs ?
In the first circuit, the LED is lighted up, whenever the Transistor, the LED is connected to is turned "on". In the second circuit, the LED is lighted up, whenever the transistor next to the LED is turned "off".
The second way of connecting the LED is favourably, because it is not affecting the RC circuit .
if only i had this video when i was in college :(
Great video!!
+premankerto It's never too late to learn how things work.
Imagine what the fill-in to "if only had this ____ when I was in college" will be 20 years from now. And I agree with HomoFaciens, it's never too late to learn. I tried and failed to learn about transistors when I was a kid, and a few times as an adult. Now I'm an old fart and I'm finally getting it. And it makes me very happy.
Dan Nuttle
Yes, nothing makes me more happy than having solved a problem or learned something new after a long time.
awesome video thank you!
Maja aa gaya..🎉😊
What are you using for the thick "bus wire" that you use to connect all your components together with? I'd like to build some circuits this way too.
I used 0.8mm welding wire, because I have enough of it. 1mm copper wire is not that stiff, but the solering joints are more stable.
Thanks for the answer.
This seems to partially confirm what I was thinking. The discrepancy is immediately after this. When the switch is pressed the upper plate of C2 jumps to 0V. T2 goes OFF and T1 ON through R3. Now the left plate of C1 is around 0V and the right to -9.5V. This should force the upper plate of C2 to -9.5V.
At this point the time should be dictated by C1 (not C2) that will charge always from -9.5V. I did some simulations that seems to confirm this. What's wrong?
Thanks :)
Good evening! Do you have the schematic for the bistable multivibrator? and also the components used. thank you in advance :)
The working principle is identical when using non-polarized capacitors. When using polarized devices, the negative terminal must be connected to the base pins, or else the circuit won't work.
Could you tell me the parameters of R1 and R2 resistors from first example? (0:30)
Is it 200k?
R1 and R2 limit the base current, thus the value depends on the used NPN transistors and the supply voltage. Since small signal transistors should be used, a value of 100k will be be OK. I used darlington transistors type BD175 with a value of 1M for R1 and R2
HomoFaciens
Thank you!
I believe putting the switch between the base/emitter junction of T2 could be misleading as the switch when on could take some of the charge of the capacitor and the intended timing design would be effected. I would say it is better to put the switch across collector/emitter of T1 where it would momentarily replace the action of T1 and the timing would not be effected at all and the capacitor charge would be used through R2 when T2 is off and T2 will clamp the capacitor voltage when its base emitter juncton becomes forward bias.
The text written on the circuit diagram loses the diagram, and it would have been better to make the circuit smaller with the written text underneath not blocking any part of the circuit. Otherwise it is a good Transfer of Knowledge session.
I will keep that in mind when overhauling the video sometime. Thanks for sharing your thoughts.
Great! What i was looking for!
Just let me one question: If i pick out one of the leds, will the bistable multivibrator still vork?
I'm planning a small scale aquaponics, and i want to trigger the pump vith this and two float switches. When the tank is full, one switch closes and the pump starts to sip out the water. When the tank is empty, an other float switches close and it will tur off the pump thru this circuit.
But i don't need any other thing to suck my power (aka other stable beside the pump), so i want to know what if i just close the circuit without an other resistor?
Thank you for the awnser, and sorry for my bad english
Dewsy Sipos Of course, the LEDs are just used to visualize the switching state of the circuits. The bistable multivibrator will do the job. Use a third transistor to control the pump (capable of switching the current drawn by that device). It won't work if you connect it directly to the circuit (intead of an LED).
Thank you!
Meanwhile i found this on ebay:
www.ebay.com/itm/321486158073?_trksid=p2055119.m1438.l2649&ssPageName=STRK%3AMEBIDX%3AIT
It directly says the 12V pump and the other as an open circuit, so i guess i found my solution, based on your video.
Thanx again!
Dewsy Sipos That circuit will do the job (as long as your pump draws less than 1A).
gutes video :D
What a nice video!! Ive got a question... How did you find out the value of R1 and R2 in the bistable circuit...! Thanks... :)
I'm so subscribing!
How long you practiced you accent?
Thank you for this fast-moving video (I'm glad there is pause and rewind!) I have not gone through the whole thing but I have a question about the early part of the video. You show a perfectly symmetric circuit with two transistors (but no capacitors yet). Why is T1 switched on first, instead of T2? The circuit appears perfectly symmetrical. I'm pretty sure the answer is that, due to tiny differences in every individual transistor, one "wins", although we can't predict which. While it is switched on, the other must remain switched off (and that part I understand). I'm now going to set up this circuit and try a whole bunch of 2N2222's and see what results I get.
I've answered my own question, if anyone is interested. The answer is that there is more than the transistors involved (which I should have realized). I put in a switch to turn the current on and off quickly and easily. At first, T1 seemed very heavily favored. It would switch on much more often, 2 to 9 times in a row (usually at least 5), then T2 would switch on once. Then I swapped the transistors. T1 (the former T2) still switched on more often, but it would usually win maybe 1 to 5 times in a row (5 times was fairly rare), and occasionally, T2 would switch on twice in a row. I then realized that the transistors involved also have their own tolerances, and the transistors on one side were playing a role in determining which side was most likely to light up first.
A really great answer to your own question! I never did experiments around the turn on conditions of my multivibrators. I simply accepted that one of the transistors "wins" over the other.
Thanks for sharing your thoughts and results.
yeah and the resistors and the caps which have about 10-20% tolerance, so the circuits are not balanced at all and one will almost always win over the other
muy buen video
really awesome
sarita jaiswal Thanks!
the value of component can be calculed .
GET TO D CHOPPA!!!!!!
chris lunsford ...if you tell me how to get there?!?
HomoFaciens LOL, he's an ADM fan (Austrian Death Machine) its from Total Brutal - its actually pretty comical if you like metal.
ChopN Hack Thanks for that hint. Metal is for machines ;)
chris lunsford no... to me, the joke come from "Predator" movie. "Get to da choppa" is an Internet mème. He said that because HomoFaciens voice/accent sounds like Arnold Schwarzenegger. Am I right Chris ?
+Gregory97133 True, that is a legendary meme. I've seen all Predator movies :D
superb. :)
Nice
What is the value of R1 and R2?
Have a look at my project page:
homofaciens.de/technics-base-circuits-multivibrator_en.htm
Good evening. The circuit I need is the first of the video "Transistor switching another transistor (00:17)." The resistors R1 and R2 are both 100K? Can I use BC-547 instead of BD-175?
Thank you very much.
this also teaches you how to debug/analyze unknown circuits.
nice, now a latch circuit to detect the forbidden state for parallel switches to cause no logic change on the output "port", such as, reading input "portA" and detecting more than one port/pin is active (forbidden state), so that the output does not change on output "portB", until only one port/pin is active at a time, to implement or realize a circuit (for example) a channel select for a transmitter or receiver... or, even a realization of the logic switch/multivibrator circuit with a series switch to "scan" a range of channel selection... (a single series switch (single input "pin") that will control (select which output "port" is active) a complete parallel output "port" for such an implementation of channel selection (for example, a transmitter or receiver module)... would be nice too...
chris lunsford Something like a multiplexer / demultiplexer? th-cam.com/video/Zz7mcHUNWjE/w-d-xo.html is my video about computing.
HomoFaciens yes, very similar to such a circuit you mentioned, only more like an ASIC (or a cheap, not so universal MCU), with a small set of instructions embedded to detect, say, in a simple 2 bit circuit, if input port is = to 3, no change to output ("forbidden state")... until input port is = to 1 or 2, then set output to the desired output "channel" or corresponding "port/pin"... with some delay (astable multivibrator) on the clock line of the FF circuit to smooth out the I/O control... or, simply decrease the propagation time of the circuit for a less quirky, less sensitive "debounce"... this is as far as i could imagine such a circuit to be as simple as possible and replace bulky analog control switches, which, could be faulty if the operator does not take care to which switch is on/off... i have to wonder if you make any of your displayed circuits micro... and thanks for the tutorials!
chris lunsford Since microcontrollers became very cheap, they are the devices of my choice for problems like that (and even more complex ones). They are tiny, reliable multi purpose tools and so usually much better than analog circuits.
The circuits in my videos are especially built to demonstrate the functionality rather than for productional use...
this is supercalafrajolisticspalodocious meaning super exiting
Now i can make a voltmeter
Also called Flip/Flop, circuit
Yes.
Donard Tlump is doing Erectlonics! Oh my God!
Thank you, Stephen Hawking, for the great video.
Youre welcome!
...but I'm not Stephen nor Arnold, but just a man with a GermanEnglish accent ;)
I also built one here :th-cam.com/video/X20urIf-7L8/w-d-xo.html