So this morning I have placed an order for the current sensor amplifier max4172:tunneldiode.blogspot.com/2020/… 1 hour later… Circuit fantasistDec 14, 14:44… instead to make it yourself? In general, this is the better solution if your goal is the element under test… tlfong014921Dec 14, 15:14I didn’t catch you. I order the 8 pin SOP chip, so I need to use the SOP 8 top DIP 8 adapter board and hand solder the SOP chip to adapter. I forgot where I placed my SOP to DIP board, so I need to order some more, in case I could not find my old ones. I will also order ICL8038 through hole chips and DIY a fixed triangle sig gen, instead of using the bigger, hard to adjust module. tlfong01Dec 14, 15:43This is the adapter board for max4172:SOP8 to DIP8 adapter board
item.taobao.com/…tlfong01Dec 14, 15:56This is the order for MCP4725:tunneldiode.blogspot.com/2020/… 1 hour later… Circuit fantasistDec 14, 17:16OK, I will look at them after my on-line meeting with my students where we are making “ideal diodes”:) See en.wikibooks.org/wiki/… and en.wikibooks.org/wiki/…. 4 hours later… tlfong014921Dec 14, 21:10Ha, I watch your students doing the lab, and then more realized why I have an inferior complexity when talking to the real EE pros. I need to first introduced my background, when I studied the EE diploma in a sort of community college to be trained as a technician repairing radios in a Philips radio manufacturing factory, or American semiconductor testing plants. In short we learned more practical things, and not emphasizedon theories.So, as I often said, after the EE diploma, I still don’t know the meaning of opAmp virtual ground. I also don’t know the deeper meaning of positive and negative feedback. Also we almost only used the locally made cheap equipment for repairing radios and the more expensive equipment was always locked in the cabinets. (1) So my first surprise was seeing your students can actually hands on, touching the high class equipment which I think are for industrial grade R&D labs.So, as I often said, after the EE diploma, I still don’t know the meaning of opAmp virtual ground. You should remember that not too long ago, I mentioned that I was very grateful for the two YouTube guys D Jones and the other name I forgot, explaining the meaning of virtual ground. I never dreamed that I can “investigate” the deep practical virtual ground.(2) The other things is about dressing code. I must first mention that in those days in my city, a large proportion of people are refugees. So when I looked back, I should be dressed as a refugee in college. I still remember that I only had two cheapy coats and two jumpers which I wore for the whole winter. So I was so surprised to see your students/tutors dressed so smartly and fashionable in the lab.Of course many years later our community collage upgraded a polytechnic and had business and even fashion design departments. Well, I am not complaining, because in those years only less than 3% of those eligible to enter a university, and perhaps 5% could go to a technical college. So fast forward decades, you should see why now I am so keen to make a (tunnel) diode oscillator, playing with opamps and ADC/DAC etc.It is sort of a healing process, or repairing of my broken dream of not being able to go to America to study EE in a University. HongKong EE/ME industries did not go well after my graduation and technician years. Luckily I had other chances to study IT and software engineering and can still earn a decent living. Now the time has come to show off my software engineering knowledge and skills.For the MCP4725 12-bit ADC, I am using high class programming techniques call “Data Driven Programming” style to power the tunnel diode to hopefully force it to enter the Negative Dynamic Resistance region.Just thinking aloud, sorry for all the typo errors. Almost bed time, see you tomorrow. Cheers. 9 hours later… Circuit fantasistTue 6:35Hi Fong, Again, I admire your gift for expressing yourself warmly and in such a human way. This is very rare on the web … as if people there have lost their ability to communicate naturally … Circuit fantasist5557Tue 6:51Regarding the emphasis on “theories”… Maybe the reason is in me simply because I was created that way – to look for the idea and after revealing it, to explain it to others. At the same time, I am a practitioner…For example, yesterday I changed the timer of the stair lighting in the building where I live. For this purpose, I did some experiments with the buttons on the floors to find out if they are working. Also, I had to figure out the idea of the timer to make sure it was damaged. Of course, these are simple but still practical skills that require some intuition and experience … especially since it is not safe … Circuit fantasistTue 7:43Virtual ground… It is a simple but difficult to understand concept. I myself continue to look for an even simpler explanation of this phenomenon … but in a more general form … 9 hours later… Circuit fantasist5557Tue 16:24Ok, let’s try to explain it in a simple possible way: “Virtual ground” is simply a “voltage copy” of the real ground; this is the essence of the virtual ground phenomenon…So, to create such a “copy”, you simply need a voltage follower. Connect its input to the real ground and take the virtual ground from its output. The simplest voltage follower is an op-amp whose output is connected to its inverting input. Thus, the output voltage is subtracted from the input voltage at the non-inverting input… the difference is amplified many times and appears at the output… and so on so forth…This can be explained in a human-friendly manner by personalizing the op-amp. Figuratively speaking, the op-amp “compares” the voltage at the non-inverting input with the voltage of the inverting input and changes it until the former becomes equal to the latter…Read the latter as: Figuratively speaking, the op-amp “compares” the voltage at the inverting input with the voltage of the non-inverting input and changes it until the former becomes equal to the latter. Circuit fantasist5557Tue 16:39From this perspective, every op-amp circuit with negative feedback contains a follower (another wisdom which cannot be found in “reputable” sources). Even the inverting amplifier contains a non-inverting follower inside – the voltage of the inverting inputs, as above, copies the voltage of the non-inverting input… and, if the latter is zero (real ground), the former will be zero as well (virtual ground)…If we put a resistor (R2) in the connection (negative feedback loop) between the output and the inverting input, the op-amp will continue keeping a zero voltage of the virtual ground…But where is the input voltage here? We include it to this following system as a “disturbance” (another wisdom). For this purpose, we connect the “disturbing” input voltage source through a resistor (R1) to the virtual ground. The op-amp reacts to this “intervention” by raising its output voltage… and we use its “reaction” as an amplified output voltage. But there is a virtual ground as before…Ohh… I have to prepare for the next meeting with my favorites. We will discuss, as yesterday, diode circuits… a very interesting topic… Nice to see you later… 3 hours later… Circuit fantasist5557Tue 20:06The equipment in my lab is quite old. There is a need for modern digital oscilloscopes and functional generators. But because I am an “old war horse”, I can handle any situation…In terms of dressing, these students now have the freedom to dress as they wish. And at the time I dressed modestly. But in general, Bulgarians and especially women pay attention to their appearance … also to the home and the car … I think this is typical for small nations … 2 hours later… tlfong014921Tue 21:49@Circuitfantasist Many thanks for your detailed explanation of the idea of opAmp virtual ground, using the analogy of the “voltage copy” of a real ground. I have never heard of the thing “voltage copy” so I think I need some time to digest. It would be nice if you can give a block diagram or schematic of the opAmp show the resistors R1, R2 etc. Or you can refer to one relevant chapter in you WikiBook of opAmp.Nothing urgent at all. I found that your explanation is a bit too hard for me now, because I have forgotten many of the basic concepts, and your descriptions like the following is indeed very confusing: “… Even the inverting amplifier contains a non-inverting follower inside, …” So I am reading the Wikipedia to refresh or learn new things. I need to study carefully the deeper ideas of “common mode”, “negative feedback”, “small signal transistor model”.I indeed have the feeling of first time to learn how to drive a car, or swimming, when the teacher says driving or swimming is “easy”, but to an newbie, that is a very different thing.In the mean time, I am trying to learn how to use python to import the matplotlib to plot the simple raw data of my first tunnel diode experiment. I am making a programming log in my blog, but you need to bother to understand anything for now. I will show you more when I can really plot something. The link is this:tunneldiode.blogspot.com/2020/…. Bed time now. See you tomorrow or day after tomorrow.Ah, yes, I forgot to mention that my first impression of your lab equipment such as power supplies, are desktop models, so of course more impress than my cheapy Amazon hobbyist models. However, when I read further, I found the computers in your lab are very out of date. So I agree with you that you need to upgrade some of the equipment, such as the digital oscilloscope. 7 hours later… Circuit fantasist5557Wed 5:24I will try to explain the inverting amplifier in another nonconventional way (you can find millions of conventional ways on the web). The general idea of this circuit solution is to set two voltages (input VIN and output VOUT) in some proportion, e.g., VOUT/VIN = 100. Then we say that VIN is amplified 100 times (with gain of 100). VIN is an external voltage; so we have to change VOUT so that it is always 100 times higher than VIN…For this purpose, we compare the two voltages by a network of two resistors in series whose resistances R1 and R2 are in proportion R2/R1 = 100. This is a passive summing circuit with weighted inputs (1:100) that can be thought of as a kind of “electrical scales” or a “mechanical lever” (Bob Duhamel has such a movie)…In 2008, my students and I created a Wikibooks story about this “elegant simplicity”. At the end of the story, we showed how an inverting amplifier is made by this network…Let’s continue this amazing story about the legendary circuit… To compare the two voltages, we have to subtract them. So, VOUT should be with opposite polarity. Then we change VOUT until the result of the comparison (subtraction) – the voltage of the middle point between the resistors, becomes zero… and we do it continuously. This point behaves as a ground although it is not a ground; that us why it is called “virtual ground”…In the circuit of an inverting amplifier, the op-amp does this donkey work”. It “observes” the virtual ground and changes its VOUT so that to keep zero voltage at this point.As a result, VOUT/VIN = -R2/R1 = – 100. 5 hours later… tlfong014921Wed 10:34Ah, your story using R1, R2 network make things a little bit clear. You remind me of Bob Duhamel’s video using a ruler with a lady. I don’t exactly understand his story. But with your story together, I am progress a little bit forward. I am very slowly reading the Wiki article on uA741 to refresh my memory on old things, at the same time relearning some new things, such the the “Hybrid T small signal model of BJT” which I did not know what is going on when the teacher talks about it, … 😦 2 hours later… tlfong014921Wed 12:08Ah, your WikiBook discussion is very good in explaining your basic Voltage and Current ideas, as a background of understanding the opAmp virtual ground concept. As I said, I am refreshing my memory and relearning things I did not understand in college, when studying my rusty EE diploma, in Hongkong Technical Collage. I need some time to warm up.
2 hours later… Circuit fantasist5557Wed 13:56Here is an attractive movie about the “living voltage diagram” – photos.app.goo.gl/…… a very sophisticated experiment…And here is the explanatory text from the WB story above: “Software. Now let’s start a program that can visualize the voltage diagram on the screen as a “living” animation. For this purpose, the program make computer “interest” in the local voltages in three key points – the left resistor’s end point, the slider intermediate point and the right end point…… Let’s then satisfy its curiosity:) by connecting, for a start, the DAC1’s output to the ADC1’s input and the DAC2’s output to the ADC2’s input; then, connect the ADC3’s input to the slider. We can control the output voltages of the two DACs by the keyboard arrows; thus the two DACs act actually as programmable voltage sources…… The computer measures continuously the three voltages (VIN1, VIN2 and VIN3) and draws three voltage bars whose length is proportional to the voltage magnitudes. Finally, it connects them with a line representing the envelope of the voltage diagram.”Another but shorter movie of the screen: photos.app.goo.gl/…. Do you see any connection between this geometrical interpretation and the Bob Duhamel’s “video using a ruler with a lady”? Circuit fantasistWed 14:34And something very interesting in CD – electrical.codidact.com/… where I was punished with -1 instead of being rewarded for what I reported… tlfong014921@Circuitfantasist Ah yes, the short movie is good to complement the Wikibook discussion. However, there is not subtitle in words or speech with it, so that is not very helpful, comparing with Bob Duhamel.Ah, “punished with -1 instead of being rewarded for what I reported …” is good for your mental health. Haven’t you heard this lady singing? “What Doesn’t Kill You Makes you Stronger – Kelly Clarkson 2011dec14 373,573,120 views”:
youtube.com/…. Happy listening. Cheers. 2 hours later… Circuit fantasistWed 16:51Nice song… 1 hour later… tlfong01Wed 18:08And one day you think you are as strong as the bounty hunter guys, you can listen “The Danish National Symphony Orchestra”:
youtube.com/…Circuit fantasistOK… Only to note the long movie is better since it shows all the possible combinations between the voltages… tlfong014921By the way, I just finished the first data conversion part of my rpi4 thonny python, declarative, newbie proof, tunnel diode I-V curve matplotlib plotting function. Will show you after my locking jog and supper. See you later. Cheers.Did I miss something? Do you mean the long WikiBook discussion with the pretty young lady? But there is no subtitle or comments, or PC programming. 🙂 Anyway, I need to go. See you late this evening or tomorrow.And if you use matplotlib, you can do animated GIF, user interactive interface. This is what I am trying to do next, plotting the tunnel diode I-V curve as animated pictures. 7 hours later… Circuit fantasist5557Thu 1:43I meant my movie showing a “living voltage diagram” on the screen of Apple II… It gives a very good notion about the R1-R2 network that is widely used in op-amp circuits… BTW, in the early 90s, I was interested in TURBOPASCAL. Then I made a similar attractive experiment – “living load line”. It was implemented on the base of a data acquisition system inside an IBM PC. I have printed screenshots. 2 hours later… Circuit fantasistThu 3:42Maybe, my answer would be interesting for you? 5 hours later… tlfong014921Thu 8:42Do you mean your answer on Schmitt trigger? I skimmed your answer but found it too long for a morning read. Perhaps I can check it out later. I did not learn Schmitt trigger in my EE diploma, so I am interested to remedy it. So you see earlier I assembled a Schmitt trigger triangle wave gen and I will use it later for the tunnel diode experiment.@Circuitfantasist Well, I did also once use Turbo Prolog in my IBM PC days. Actually the python program I am writing now uses some of the programming ideas, such as “declarative programming style (not procedural or OO), using predicate logic etc, .. In the deleted CD chat, I remember towards the end, I told you that I will use Occam’s Razor style to answer my own question of the tunnel diode’s missing NDR plot. You see I am still working on it. 🙂BTW, I do thinkg Turbo Pascal good for small programming projects. 3 hours later… tlfong01Thu 11:21About the R1 R2 notation. If you goolge opAmp images, you whould find how many images are using Rf, Rg, and Rin, and how many using R1, R2. As I often say, you are chasing your audiences away, if they don’t know your notation, and no diagrams along side to help to figure out, … 3 hours later… Circuit fantasist5557Thu 14:00“Rf” is misleading since it is not only the resistor constituting the feedback network; both resistors make it (they form a voltage divider driven from the side of the output). Maybe “Rout” is more correct…I prefer to use “R1” for the input resistor (between the source and “-” input) and “R2” for the output resistor (between the op-amp output and “-” input). Of course, I always use drawings in my explanations but here it is not convenient. 2 hours later… Circuit fantasistThu 16:14I am discussing now another relatedgreat idea with my students – the so-called “sense amplifier”… 6 hours later… tlfong014921Thu 22:07The matplotlib is very newbie friendly. I just spent 10 minutes skimming the beginners guide, read the demo program, and only made a couple to trials and errors and successfully drew the following Tunnel Diode 2SB4B I-V Curve, using the crude manual measurements I listed in my question.
Now I am coming back to v2.0 of the tunnel diode I-V curve plotting proposal. tunneldiode.blogspot.com/2020/…. As I said earlier, this v2.0 hardware will use (1) 12-bit current sensor, (2) 12-bit ADC. Both toys arrived this afternoon, just in time to start playing. 🙂 3 hours later… Circuit fantasistFri 0:48I think only Edison has worked so hard… well, me too:) Here’s my new blog post and CD. 12 hours later… tlfong014921Fri 13:00I agree you can have your reason for using R1, R2 in your opAmp notation (and your “vertical bar” and “circular loop” to denote V and I).
The problem is ***consistency***: If 90% of the EE guys are using R1, R2, me newbie will definitely follow, otherwise I would not be popular among my friends, colleagues, and most importantly my students, who would have a miserable journey in their EE career. To assure easy learning curve, I strongly recommend the newbies the following tutorials: tunneldiode.blogspot.com/2020/….(see full text) 3 hours later… Circuit fantasistFri 15:35You are right about R1-R2 annotation… Very useful and systematic learning scenario… I forgot to write you that I sent you an email to share something more specific … 4 hours later… Circuit fantasistFri 19:20I have written some “black thoughts” in my reply to your last email:) 3 hours later… tlfong01Fri 22:38Ah, I have never heard of the term “black thinking”, so I googled: healthline.com/health/….And you remind me one of the world’s 50 thinkers I admire: medium.com/@preetibhonsle/…. 3 hours later… Circuit fantasistSat 2:12Maybe “dark thoughts” is more correct… 9 hours later… tlfong014921Sat 10:54I am not sure how to present my tunnel diode project. So I have bee browsing forums to get some ideas. I looked at Writing.CD and Writing.SE and found them good. I am particularly keen to see how other “Test Driven Developers” do. The first couple of Q&As I read are good, including these: (1) writing.codidact.com/posts/…
(2) writing.stackexchange.com/…. So I am following some of their advice in my tunnel diode test programs.(see full text) 3 hours later… tlfong014921Sat 13:27So I have cone the MAX4172 current sensing amp SO8 to DIP8 adaptor soldering jog. It took me some 30 minutes.
tlfong014921Sat 13:58I am planning to write the story of “How does an electron slip through a Tunnel Diode?” So I am reading more posts in Writing.StackExchange. I am very surprised to find that this Writing posts also give me a very good impression as SO did some 8 years. Example: “What is the best way to learn technical writing? Asked 8 years ago, Viewed 2k times”:
writing.stackexchange.com/…. Cheers. 2 hours later… tlfong014921Sat 16:19Now I am reading MAX4172 datasheet. This reminds me why earlier I said using any answers based on opAmp is too low level. Appropriate technology is system integration of opAmp based cct.
2 hours later… Circuit fantasist5557Sat 18:38Writing was interesting for me when I was younger… Now I am mainly interested in the content and less in the form of its expression…But yesterday I was thinking about something related to this – isn’t it possible to somehow integrate text and graphics into one… let them be one thing? Because this reference from text to figure is very artificial … and the way of implementation is very different. I wonder if hieroglyphs are a more integrated way of conveying content. I don’t know, maybe you will say … This must sound very naive …In fact, I do something similar by describing a picture in words and by suggesting text in a picture … 17 hours later… tlfong014921yst 11:51Yes, your innovative idea of merging text into pictures is inspiring. One way of doing it is to hide the text behind the picture. When you click the picture, 1,000+ words would jump out explaining the picture. Below is an example showing your idea.
Now when you click the picture of the negative resistance, Wikipedia would come out explaining the “N curve”. And when you click the “superimposed I-V curve” the corresponding WikiBook would explain the colourful picture. tlfong014921yst 12:06By the way, I have been criticizing your hard to understand colourful, hand drawn, superimposing I-V curves picture. But you do inspire me to updating it to make it simple for newbies to understand. By plan is summarized below: (1) Use 4 or more MAX4172 current sense amp to measure, at the same time, four different two terminal devices (resistors, diodes etc). (2) Use one or more MPC4712 I2C built in EEPROM DAC to individually or grjoup power the diodes.(3) Use MatPlotLib to plot the superimposed colourful I-V curves, with animated images, user interaction etc.Ah, locking down lunch time! See you later. 7 hours later… Circuit fantasist5557yst 19:24Hi TL Fong,
I fell asleep today and now I’m in a hurry to go for my usual walk in the park. Just to tell you that I found some solution to the problem with my Flash movies. I made them as executable files that contain a Flash player in themselves. They are full-fledged Flash movies. I have sent to you by an imejl the first four of them dedicated to the most basic building blocks. Cheers! 9 hours later… Circuit fantasist55574:26Hi TL Fong, Today I started writing a big new and very interesting post about our chat here… Interesting thoughts are born in our conversations and I decided to extract and collect my most significant “pearls” in a post. I hope you will approve my idea.If you want, you can make a reciprocal post about your ideas. I just wonder how it is possible for a discussion with only one interlocutor to be so many times more fruitful than the many questions and answers on these sites?Your idea of mixing text and picture is very interesting. Flash provided great opportunities for such tricks and I was very fond of them.Your idea about IV curves is very interesting. As I probably mentioned, in 90s I conducted an interesting experiment where two imposed IV curves lived on the screen. I intend to write a story about this experiment that will be illustrated with printed screenshots. 2 hours later… Circuit fantasist6:36I have created an initial post about this chat. Later, I will structure it… The last message was posted 5 hours ago.