Excellent video Dave. You went through it the old-school way, showing the proper analogue hysteresis solution rather than what 99% of people would do, just add a Schmitt Trigger module/circuit. I also learned something from your explanation of the digital version Of course, even those who understand how it works will still pick the IC that has the Schmitt Trigger built in because, let's face it, it's easier. Kudos to you mate, you obviously have a deep understanding of electronics but also have the knack of making it entertaining and easy to follow.
Thank you! If only I could travel in time 24 years ago and show this video to my past self... I've spent endless hours trying to debug my circuits. But I can show this video to my students. Thank you very much! (excuse my english)
Dave I am second year Electronic Systems Engineering student and your videos have been - to put it mildly - invaluable! Thanks for the time and effort you put into sharing your knowledge and experience - B. Decker, Cincinnati Ohio
This causes so many problems in software when the hardware designer misses it. EXCELLENT VIDEO! Also the software designer should account for this and best when both do. But this is very frequently missed!
Thank you for this video Dave. although I learned electronics for 2 years, I completely missed the slow raise time issue. I've heard of the schmitt trigger of course, but I didn't know it was so important.
When I was quite young I had this explained to me, describing why a house thermostat has two trigger levels, so that the furnace doesn't keep turning on and off, which stresses it. Recently I was talking with a friend who owns some property with a well and storage tank, and same thing so the well pump doesn't cycle too much. So much hysteresis!
Exactly. We've had a drought here for a few months and I've been messing with the water pump and tank lately so I checked if the system had hysteresis and it surely does. It stops pumping at 60psi and starts at 40psi. Synthesizer circuit builders love schmitt trigger inverters like the 40106 or 74C14 because they have six inverters in one IC and can be made to oscillate with just a resistor and a capacitor.
I have been trying to design an overload cutout digital circuit based on a comparator measureing voltage across a shunt resistor. It was oscillating. Which I discovered after making an SMT board. Much puzzlement later I came across this video. It was literally a case of adding a single +ve feedback resistor and the problem just immediately went away. You saved me so much hassle!
I came across schmitt trigger when I was thinking of a hardware solution for button de-bouncing. I didn't know about STs so I made a 555 circuit to provide the hysteresis. Later I found out about ST and life was easier.
Brainstorm4300 Check your micro's data sheet. AVRs have an internal Schmitt trigger on their input circuit, the micro you're using might also. an external Schmitt circuit may be unnecessary.
In my second year at university, ages ago, I had a similar problem with a very slow counter. It worked at home but, as soon as I was showing it to the teacher it started to play these tricks on me. The thing is, the teacher didn't know why either and gave top marks anyway. Wish I had know about Mr Schmitt.
You sir have be invaluable in my understanding of electronics. I have not found another RUclipsr who has been more valuable to my understanding of electronics. You've been the reason I've been able to stay upbeat while dealing with problems that plague the "Young Players" as you say. Thank you from the bottom of my heart!
When I saw your op amp at the top left, I wondered, "if you're using an op amp to create a Schmitt trigger, where are the hysteresis resistors?" But of course, you took it slow and simple, as a good teacher should. An excellent tutorial.
Our 74161s at lab would sometimes go crazy with the old clanky clock generator we had, and we would blame the ICs. I think I know the actual reason now! Thanks Dave!
Superb Dave, Wish you had been a teacher at my technical college doing electronics..... Love the fundamental Friday's. Maybe you can work this stuff into some small projects that pull all these principles together? Keep up the fine work!
At 25:45 you see two oscillations. One at 0.5V peak and the other at 1.5V peak. The 1.5V peak could still cause problems. A small capacitor (10pF) across the positive feedback resistor can fix that problem.
A Siglent generator I see you using.... With your slight encouragement I bought some Siglent equipt....I am learning so much at my tender age of 41...LOL. Thanks!
Crazy! Just today I got my art of electronics an the first page I open is about schmitt triggers, also on friday I had a lab exam in my university about schmitt trigger nand gates! What a coincidence.
Positive feedback for digital hysteresis can come from two series inverters; A=not(not A). The feedback element (say 1 MOhm) connects the output to the first gates and the input passes through a series resistor (say 10 kOhm) before the first gates. These choices give about Vcc/100 hysteresis.
Thank you so much Dave. Your videos are really helpful to understand the fundamentals of electronics. I wish I had a teacher like you in college. Whenever I am stuck at some point I will search the concepts in your playlist first. Your video tutorial helps me a lot.
I make a slight distinction between a "Schmitt Trigger" and a "Comparitor with Hysteresis". A schmitt trigger will "latch" into one state once triggered, and will stay there until the input transistions to close to the opposite state (large amount of hysteresis). "Comparitors with Hysteresis" generally just have enough hysteresis to avoid multiple transitions due to input noise, and will transition close to the designed threshold (small amount of hysteresis). Don't use Schmitt Trigger IC's where the transition voltage level is important.
Thanks Dev and it has been very useful to understand insight about it, though I have been using Schmitt trigger more for debounce signals. Thumbs up and eager to see next session.
Hysteresis is also used in coding when implementing debounce on push buttons. You set a trigger value, say 20, then you have a "tank" var which is incremented when a button HI is detected and decremented when a button LO is detected during your loop. You never let the tank rise above the trigger value or go negative so you have to cap it in the code. If your loop detects the tank is equal to the trigger then the button status is set to "pressed" if it detects the tank is 0 then the status is set to "not pressed".
Fantastic video! I've been considering making something like this to help my customers (I develop new logic ICs for a very large semiconductor company) but just haven't found the time to do it. So glad that you beat me to it - yours will likely help far more people than mine would!
Excellent video Dave! Just a wee thought on the breadboard shots though. There are a lot of 'young-players' who watch your knowledge (and entertainment) channel. For that, it will help so many if just a little more concern could be shown in keeping to a consistent standard for circuit element inter-connection wire colours. We see this as an area where students most frequently encounter problems during circuit assembly and debugging - too many different colours on the same net with no discernible conventions for colour choice - or too few colours throughout. Us older, experienced players do get rather relaxed and complacent about these things.
Excelent explanation and vid, just one observation, the final fix to pot oscillation, it's a simple Op Amp as a comparator, a voltage level detector, without hysteresis. Hysteresis have two reference points just how you mentioned it, regards.
Reminds me of building an (very simple and slow) serial optical (laser) data transfer model at school Transmitter:PC -> RS232 -> Transistor -> Laserdiode Receiver: Phototransistor -> Schmitt Trigger -> RS232 -> PC
Liked this. Always wondered how ST works in IC's. The Schmitt Trigger was my first circuit ever, made it for a fishtank heater on an oversized, crudely etched PCB. It was a more classic two transistor ST with a relay on the collector of transistor 2 that also was part of the ST - and it didn't work. Tried and soldered for weeks until I used a relay with higher Resistance. Oh, what joy hearing that *CLICK*. It started my electronics addiction. Would love to see you show that two transistor ST sometimes...
Thanks a heap, that solved my problem. I wish I knew about this earlier. I was originally thinking it was noise in the data line, but after this video and a simple resistor did the trick :)
I use a Schmitt triggered inverter (74HC14) as the input to an RC circuit to form very rudimentary "neurons" in my robots. It waits to trigger till the input rises passed it's threshold, and then the output flips. It's not a true neuron, by any means, but it subs as a rudimentary one just fine!
Using a Schmitt Trigger to eliminate switch bounce is not really the best solution. You can have switch bounce that goes rail-rail and it can be quite slow compared to the response time of your digital circuit. It's better to use a flip flop type circuit to eliminate switch bounce or to put a delay in the software if it's being fed directly into a micro or something like that.
Putting a properly dimensioned low-pass RC filter between the raw input signal and the Schmitt Trigger should work, too. (Which will effectively introduce some delay between the input and output transition.)
I must have missed it but how did you decrease the initial rise time. Is the rise/fall time a function of your signal generator? Thanks...thumbs up "mate"....PEACE
The difference voltage on the comparator inputs is easy to calculate. It's 1 divided by the gain. A gain of 100,000 to 1 for example would result in a voltage of 10 nanovolts. So small no multi-meter would see it. The noise induced in the cabling to an o'scope will completely swamp out this voltage as well. So assuming it's 0v is a pretty damn close to real world measurements. Plus it makes the math easy too which is the big bonus :)
Excellent video Dave. You went through it the old-school way, showing the proper analogue hysteresis solution rather than what 99% of people would do, just add a Schmitt Trigger module/circuit. I also learned something from your explanation of the digital version
Of course, even those who understand how it works will still pick the IC that has the Schmitt Trigger built in because, let's face it, it's easier.
Kudos to you mate, you obviously have a deep understanding of electronics but also have the knack of making it entertaining and easy to follow.
LOL, OpAmp isn´t anywhere near old school. The original design used tubes.
Without watching this video, I would have just stupidly added a Schmitt trigger IC.
Your videos make me learn. My college only tests me. I should be paying you instead. Thank you for your videos I have learned a lot.
I've asked myself, why isn't Dave a teacher instead? Well of coarse it's because of insterests and so.
Well he is sort of a teacher, he teaches using youtube :)
I think you underestimate the difficulty and hardships of running a school.
But did you pay him?
@@PankajKumar-zr3tv no
So I had this person from the IEEE laugh at my negative feedback shirt. Saying, "I only give positive feed back but am prone to oscillation."
Nice!
Do a program with a super high-speed counters cheap and available ns and ps :)
thanks Dave , for making electronic concepts easier and more interesting than any professor on the planet Earth, catch you next time , bye bye
Thank you! If only I could travel in time 24 years ago and show this video to my past self... I've spent endless hours trying to debug my circuits. But I can show this video to my students. Thank you very much! (excuse my english)
"Trap for young players, lets go to the data sheet!" This seems a common theme, plus I like the way he says it.
Datasheets are the lifeblood of an electronics engineer.
I know zero about electronics, but I understood this after watching. You're a good teacher.
..."A fraction of a bee's dick."
Your Aussie analogies never cease to make me audibly say "dafuq?"
Kamagatta!
Dave I am second year Electronic Systems Engineering student and your videos have been - to put it mildly - invaluable! Thanks for the time and effort you put into sharing your knowledge and experience - B. Decker, Cincinnati Ohio
This causes so many problems in software when the hardware designer misses it. EXCELLENT VIDEO! Also the software designer should account for this and best when both do. But this is very frequently missed!
Wish I had known this a month ago, when I was designing simple comparator circuit. Now it's being manufactured and it has that oscillation problem.
Time for a bodge!
Thank you for this video Dave. although I learned electronics for 2 years, I completely missed the slow raise time issue. I've heard of the schmitt trigger of course, but I didn't know it was so important.
uh oh
Watching your lectures is a PLEASURE my man! Beauty!
When I was quite young I had this explained to me, describing why a house thermostat has two trigger levels, so that the furnace doesn't keep turning on and off, which stresses it. Recently I was talking with a friend who owns some property with a well and storage tank, and same thing so the well pump doesn't cycle too much. So much hysteresis!
Exactly. We've had a drought here for a few months and I've been messing with the water pump and tank lately so I checked if the system had hysteresis and it surely does. It stops pumping at 60psi and starts at 40psi.
Synthesizer circuit builders love schmitt trigger inverters like the 40106 or 74C14 because they have six inverters in one IC and can be made to oscillate with just a resistor and a capacitor.
I wish Dave could replace the profs at my university.
So much fun to watch your videos Dave.
Thank You
Love Fundamentals Friday! It would be cool if you make videos on that category more ofthen.
Thank you so much Dave, I love coming here for these delightful crash courses on engineering.
best educational videos ever.
Lord_Vader Seriously, these are the best.
Lord_Vader Got me through circuit analysis too!
Dang, my DaveCAD license expired, my pen ran out of ink.
Bloody brilliant Dave. It is so much easier learning a component etc when you can put it into context.
We need more videos like these. You are quite skilled at these educational videos. I much prefer it to a tear down of a 40 year old bit of kit.
I have been trying to design an overload cutout digital circuit based on a comparator measureing voltage across a shunt resistor. It was oscillating. Which I discovered after making an SMT board. Much puzzlement later I came across this video. It was literally a case of adding a single +ve feedback resistor and the problem just immediately went away. You saved me so much hassle!
I came across schmitt trigger when I was thinking of a hardware solution for button de-bouncing. I didn't know about STs so I made a 555 circuit to provide the hysteresis. Later I found out about ST and life was easier.
Brainstorm4300
Check your micro's data sheet. AVRs have an internal Schmitt trigger on their input circuit, the micro you're using might also. an external Schmitt circuit may be unnecessary.
Mark Dowd I know. It was for a circuit completely made of 74 and 4000 series ics otherwise I'd have just used my software debounce routine.
You can avoid de-bouncing just by software.
Dude, after going to all other channels, that explains Schmitt Trigger, this is the best and the clearest one! thanks, man!
In my second year at university, ages ago, I had a similar problem with a very slow counter. It worked at home but, as soon as I was showing it to the teacher it started to play these tricks on me. The thing is, the teacher didn't know why either and gave top marks anyway. Wish I had know about Mr Schmitt.
You sir have be invaluable in my understanding of electronics. I have not found another RUclipsr who has been more valuable to my understanding of electronics. You've been the reason I've been able to stay upbeat while dealing with problems that plague the "Young Players" as you say. Thank you from the bottom of my heart!
When I saw your op amp at the top left, I wondered, "if you're using an op amp to create a Schmitt trigger, where are the hysteresis resistors?" But of course, you took it slow and simple, as a good teacher should. An excellent tutorial.
Our 74161s at lab would sometimes go crazy with the old clanky clock generator we had, and we would blame the ICs. I think I know the actual reason now! Thanks Dave!
Superb Dave, Wish you had been a teacher at my technical college doing electronics..... Love the fundamental Friday's. Maybe you can work this stuff into some small projects that pull all these principles together? Keep up the fine work!
I thought I already knew about Schmitt triggers, but I watched and I learned something new again. Thanks Dave!
Precisly when I need to take care of input noise on a comparator, Dave gives me a solution. Great timing, thank you very much !
I read it in books before, but it is realy much better to learn it that way.
At 25:45 you see two oscillations. One at 0.5V peak and the other at 1.5V peak.
The 1.5V peak could still cause problems. A small capacitor (10pF) across the positive feedback resistor can fix that problem.
Dave, if you are not already, you should be a teacher. Great tutorials and the aussie accent is a plus... love it. Greetings from Argentina.
A Siglent generator I see you using.... With your slight encouragement I bought some Siglent equipt....I am learning so much at my tender age of 41...LOL. Thanks!
Thanks for the block, I love when you do these teaching block, it teach me a lot.
I am very confused but also intrigued.
A perfectly fine state to be in!
In fact, being confused and intrigued is the best state to be in when learning - provided you use it as incentive to learn more.
Wow. Now i really understood about schmitt trigger. Hats off to Mr. Dave.
Please make more fundemantals Friday! They already helped me studying for my classes a lot.
Finally I got what Hysteresis is and how to use a schmitt trigger: thanks a million Dave! 👍👍👍
Doing Research for my 3rd yeah project (50hz phase detector) and this was awesome. Really happy I found your channel 👌
Every time I watch one of Dave's videos, I want to resubscribe all over again!! They're that good! Thanks Dave - forever a fan! :)
Crazy! Just today I got my art of electronics an the first page I open is about schmitt triggers, also on friday I had a lab exam in my university about schmitt trigger nand gates! What a coincidence.
I love your explanation of the schmitt trigger, I use them a lot in my arduino projects. If only this video existed when I was learning about them.
Positive feedback for digital hysteresis can come from two series inverters; A=not(not A). The feedback element (say 1 MOhm) connects the output to the first gates and the input passes through a series resistor (say 10 kOhm) before the first gates. These choices give about Vcc/100 hysteresis.
Thank you so much Dave. Your videos are really helpful to understand the fundamentals of electronics. I wish I had a teacher like you in college. Whenever I am stuck at some point I will search the concepts in your playlist first. Your video tutorial helps me a lot.
I make a slight distinction between a "Schmitt Trigger" and a "Comparitor with Hysteresis". A schmitt trigger will "latch" into one state once triggered, and will stay there until the input transistions to close to the opposite state (large amount of hysteresis). "Comparitors with Hysteresis" generally just have enough hysteresis to avoid multiple transitions due to input noise, and will transition close to the designed threshold (small amount of hysteresis). Don't use Schmitt Trigger IC's where the transition voltage level is important.
Thanks Dev and it has been very useful to understand insight about it, though I have been using Schmitt trigger more for debounce signals. Thumbs up and eager to see next session.
Hysteresis is also used in coding when implementing debounce on push buttons. You set a trigger value, say 20, then you have a "tank" var which is incremented when a button HI is detected and decremented when a button LO is detected during your loop. You never let the tank rise above the trigger value or go negative so you have to cap it in the code. If your loop detects the tank is equal to the trigger then the button status is set to "pressed" if it detects the tank is 0 then the status is set to "not pressed".
"It only needs to be a s--- fraction, half a bee's dick, a smidgen above or below..."
-Dave, 2016
you made my day with that remark.
This video was sooo much impressive than i ever wonder! The last part was absolutely genius!! Thank you so much!
Fantastic video! I've been considering making something like this to help my customers (I develop new logic ICs for a very large semiconductor company) but just haven't found the time to do it. So glad that you beat me to it - yours will likely help far more people than mine would!
I liked how you started the video with the breadboard and demo.
Great video Dave, always good to see some educational EEVblog content in my subbox.
Schmidt trigger combined with an RC delay makes an excellent switch debouncer as well :)
Thank you for this video. It is a really important issue that I never thought of enough.
Excellent discription Dave, thanks a lot!
Thanks, Dave. I was familiar with physical hysteresis, as in old electro-mechanical thermostats. Didn't know the concept was used in electronics too.
This one is so easy to understand as compared to the transistor version.
In layman's terms the hysteresis is giving the circuit wiggle room before it triggers on either state.
Was waiting for another Tutorial. Love this stuff... Thanks Dave ;)
Excellent video Dave! Just a wee thought on the breadboard shots though. There are a lot of 'young-players' who watch your knowledge (and entertainment) channel. For that, it will help so many if just a little more concern could be shown in keeping to a consistent standard for circuit element inter-connection wire colours. We see this as an area where students most frequently encounter problems during circuit assembly and debugging - too many different colours on the same net with no discernible conventions for colour choice - or too few colours throughout. Us older, experienced players do get rather relaxed and complacent about these things.
Excellent work, Dave!
Just beautiful
Thanks Dave
Great video Dave very clear and easy to follow!
Some of these sound bites are gold!
Excelent explanation and vid, just one observation, the final fix to pot oscillation, it's a simple Op Amp as a comparator, a voltage level detector, without hysteresis. Hysteresis have two reference points just how you mentioned it, regards.
Reminds me of building an (very simple and slow) serial optical (laser) data transfer model at school
Transmitter:PC -> RS232 -> Transistor -> Laserdiode
Receiver: Phototransistor -> Schmitt Trigger -> RS232 -> PC
So, positive feedback yields hysteresis / makes the output sticky.
Excellent video - theory and lots of practical examples. The best way to learn!
where i have been from so many years... your videos are very informative. thanks for your great efforts
Liked this. Always wondered how ST works in IC's. The Schmitt Trigger was my first circuit ever, made it for a fishtank heater on an oversized, crudely etched PCB. It was a more classic two transistor ST with a relay on the collector of transistor 2 that also was part of the ST - and it didn't work. Tried and soldered for weeks until I used a relay with higher Resistance. Oh, what joy hearing that *CLICK*. It started my electronics addiction. Would love to see you show that two transistor ST sometimes...
Thanks a heap, that solved my problem. I wish I knew about this earlier. I was originally thinking it was noise in the data line, but after this video and a simple resistor did the trick :)
This was an amazing video, thanks for the refresher!
I use a Schmitt triggered inverter (74HC14) as the input to an RC circuit to form very rudimentary "neurons" in my robots. It waits to trigger till the input rises passed it's threshold, and then the output flips. It's not a true neuron, by any means, but it subs as a rudimentary one just fine!
"...if you hold your tongue at the right angle" Whahahaha! Gold!
Interesting stuff. I knew of the Schmitt Trigger from electronics class in year 11, but we only really used them to eliminate switch bounce.
Using a Schmitt Trigger to eliminate switch bounce is not really the best solution. You can have switch bounce that goes rail-rail and it can be quite slow compared to the response time of your digital circuit. It's better to use a flip flop type circuit to eliminate switch bounce or to put a delay in the software if it's being fed directly into a micro or something like that.
Lucky that you have electronics class. The HSC electronics subject in Sydney is virtually impossible to find. No school does it for the HSC.
What do you mean by "HSC"?
Herbert Susmann umm, the series of tests that lets you go from high school to university?
Putting a properly dimensioned low-pass RC filter between the raw input signal and the Schmitt Trigger should work, too. (Which will effectively introduce some delay between the input and output transition.)
Thank you very much. Your teaching videos are perfect. Please make more of these.
Super simple, that Schmitt guy was one smart cookie
This can also be used as level shifter, if you need it as 1:1 it needs a stack of two inverters.
davecad is the best cad ever
Awesome stuff. I am learning so much watching these videos.
Thanks Dave!
Ahh, fundamental fridays, i wish you did more of this.
I wish you were my tronics teacher, i would have learnt a ton of things.
Thanks for the quality of your explanation ! I love those video, i'm a electronic newbie, and it is very helpful !
1989 vintage chip. Nice dave!
I was playing around with a 1976 vintage LM741 too, you might be able to see it on the breadboard
I must have missed it but how did you decrease the initial rise time. Is the rise/fall time a function of your signal generator? Thanks...thumbs up "mate"....PEACE
Thanks Otto Schmitt, thanks Dave. It is very nice and helpful tutorial.
Love the fundamentals friday! Thank ya Dave!
2:12 I died at that "OOOPS" lmao
Very nice ! Congrats! Hysteresis is a Greek word and translates to: delay in English. Keep up the good work!
I knew nothing about this, hadn't even heard of it or thought about it
The difference voltage on the comparator inputs is easy to calculate. It's 1 divided by the gain. A gain of 100,000 to 1 for example would result in a voltage of 10 nanovolts. So small no multi-meter would see it. The noise induced in the cabling to an o'scope will completely swamp out this voltage as well. So assuming it's 0v is a pretty damn close to real world measurements. Plus it makes the math easy too which is the big bonus :)
Thanks for doing my professor's job.
Aw, bloody beautifull, knew all about schmitt triggers, but I love the explanation😀
Explained better than than my college professors. Thanks!
Excellent as always
Super video, very clear explanation - blowing the rust out ;-)
Great video dave! Always a fan of fundamentals Friday
You are absolutely good! more video about Electronic please!
Learn so much from these Videos Dave, Thank you so much
Finally, I understand. Thanks a lot!