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STEM Formulas 理工公式
Приєднався 22 тра 2020
Відео
Men's Volleyball Nations League 2024 (VNL), Canada vs. USA , part2 Ottawa
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Men's Volleyball Nations League 2024 (VNL), Canada vs. USA , part2 Ottawa
Men's Volleyball Nations League 2024 (VNL), Canada vs. Serbia, Sets 1 and 2, Ottawa
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Men's Volleyball Nations League 2024 (VNL), Canada vs. Serbia, Sets 1 and 2, Ottawa
option trading: covered call writing for Canadians, Part 1
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please write your questions here, I will answer in the part 2 video.
Two blocks are connected by a massless string over a frictionless pulley as shown.
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Two blocks are connected by a massless string over a frictionless pulley as shown.
Drone Spectacular: 2023 Drone Unit Light Show in Changchun(长春), China - July 24th-26th, 2023!
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Drone light shows. This video has been filmed in Changchun, Jilin Province, China, by "STEM Formulas." 长春 无人机集群表演, 长春农业博览园主广场
Cathode grounded laser diode (or LED) driver
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Some laser diodes have their negative side (cathode) connected to the diode's metal case. If the metal case has to be connected to the ground, it is necessary to use a cathode grounded laser diode driver. This video presents a new circuit schematic for cathode grounded laser diode driver with formulas. The circuit needs one op-amp, one pnp transistor (or P-Channel MOSFET), and a single power su...
Optical holography theory, spatial frequency, some problems and solutions
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In a college or university optical class, holography serves as an excellent experiment to demonstrate the wave aspect of light. However, the theory behind the lab has not been adequately described in the textbook; it is either too concise or overly complicated mathematically. To enhance the understanding of the physics, this video provides a straightforward and clear description of holography t...
Rectangle optical block: find laterally shifted distance d
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Rectangle optical block: find laterally shifted distance d
Relativistic Quantum Mechanics: A new formulism
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Relativistic Quantum Mechanics: A new formulism
Variational derivation of Hartree-Fock single particle potential at finite temperature
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This is an explanations of late Professor Shi-Shu Wu (1923-2009)'s handwriting on the Hartree-Fock approximation at finite temperature. The whole derivation is in English. Stem Formulas kindly shares the derivation with the public for research purposes. Theoretical nuclear physics Nuclear matter Nuclear matter at finite temperature Hartree-Fock approximation at finite temperature Hartree-Fock t...
Discovering The Charming Llamas Of Northern Quebec!
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Discovering The Charming Llamas Of Northern Quebec!
Canadian Geese: Parents Supervise Their Babies Going Across the Street.
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Canadian Geese: Parents Supervise Their Babies Going Across the Street.
How the City of Montreal Cleans the Fallen Tree Branches
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How the City of Montreal Cleans the Fallen Tree Branches
Exploring Montreal's Urban Pigeon Population In The Heart Of The City!
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Exploring Montreal's Urban Pigeon Population In The Heart Of The City!
Standard model of fundamental particles and interactions
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Standard model of fundamental particles and interactions
Equation of State video 3 of 3 a formula for crystal under harmonic approximation
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Equation of State video 3 of 3 a formula for crystal under harmonic approximation
Equation of State video 2 of 3 An indefinite integral needed in solid state physics
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Equation of State video 2 of 3 An indefinite integral needed in solid state physics
Equation of State video 1 of 3 expressing P in terms of internal energy U
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Equation of State video 1 of 3 expressing P in terms of internal energy U
Two methods to solve the inclined plane problem: with friction case
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Two methods to solve the inclined plane problem: with friction case
Two methods to solve the inclined plane problem: no friction case
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Two methods to solve the inclined plane problem: no friction case
Find the smallest force make the box moving.
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Find the smallest force make the box moving.
This is brilliant, thank you!
🔥🔥🔥
I was going to comment about how circuits on exams always have ridiculous non-standard values. I guess it's to make the calculation harder or easier, depending on the problem, but you can't easily take these designs as is - good luck finding a resistor with the value of 393 ohms for example.. Then I read your comment on a more practical example. My OCD has been resolved. :D
Dear delarosomccay Thank you very much for your comment about the values, the values are non-standard in the video, in my teachings I use a software called "diploma" to organize the problems. I randomize the values so that each students get different values on his own exam, so that the students cannot just copy from each other the answers. they have to go through the calculation to get the answers.
But did you actually check to see how much base current is flowing? Blue and Green GaN LEDs are bright at 1mA, so maybe the base current could be a source of significant error. To make it irrelevant you could put the LED on the emitter leg of the circuit. As long as you have sufficient voltage headroom the op-amp won't care which side of the transistor it's on.
Dear simonlyons5681, Thank you very much for your comment. I do not quite understand the question, what is the 1mA current. what are the two LEDs, you use the two LED at the same time or what? what do you mean by the error? Please write your question in more details, I will get you back as soon as possible.
Nice explanation
Is the prism angle same as apex angle then
Dear shifra3203 Thank you for your comment, Yes, the prism angle is the same as apex angle.
In reality R1 and RF doesnt make any sense, its only for calculation purpose...because it will rise amplification factor and its not needed here. It will just create stability issues.
Great video
Thanks 🙏👍
Very good. Thanks 🙏
Why do you need Rf and R1? If you just connect the junction of the emitter and RE back to the inverting input you can set the current by adjusting Vi.
wonderful handwriting and wonderful way of delivering the idea, thank you so much
Thank you for your comments, I learned this diagram from my father, I am using it for my students in Motion and Energy course, it helped my students a lot.
😅😅😅😅😅😅well information good 😅😅
💖💖💖💖
WHAT BOOK IS THIS?
Anything for Anode grounded lasers?
Great video!!
A very good tutorial about circuits in tikz. Really love it.
Assuming a perfect opamp and sufficient headroom on the supplies, when the voltage at the non-inverting terminal is 8V, the voltage at the inverting terminal is also 8V. So the current through R1 must be 8V / 0.715K = 11.2mA. That current must also pass through Rf, so the voltage across it must be 11.2mA x 0.313K = 3.5V. Therefore the voltage across Re must be 8V + 3.5V = 11.5V, which makes the current through Re 11.5V / 0.368K = 31.3mA. That makes the current from the transistor emitter 11.2mA + 31.3mA = 42.5mA. Assuming the transistor β >> 1, then the collector current is also 42.5mA. No need for algebra, and it doesn't take 7 minutes.
Dear RexxSchneider Thank you for your comment, your calculation is correct. Very good!
I disagree, the explanation is very important to show how this circuit acts as a current source.
@@mmh1922 Rubbish. My description above shows exactly how the circuit behaves as a current source and takes 30 seconds to read. Which part of it didn't you understand? Exactly what did you find missing that was present in the video, apart from all the unnecessary algebra?
@@RexxSchneiderI respect your right to express your opinion, however, as a reader, I decide what is important to me and what is not.
@@mmh1922 Of course you can decide whatever you want for you. And I can decide to call you out when you're spouting nonsense. Not for your benefit, naturally, but for the benefit of everyone else who reads your misleading comment and wants to decide if it has any value. That's why I asked you "Which part of it didn't you understand? Exactly what did you find missing that was present in the video, apart from all the unnecessary algebra?" Your inability to address those basic questions are surely the clearest indication to any observer that your initial comment was devoid of merit.
Hi, how much is the total voltage drop of this circuit? My red laser diode needs around 800/850 milliampere and it drop with 2.2- 2.7 volt. Can i use a single li ion 3,7 volt? and Which op amp and bjt/mosfet do you suggest me in my situation? Thanks you
Dear Sir, Thank you very much for your comment. For your situation, you can choose the following: RE=0.5 Ohm (high power resistor). If you use a MOSFET, the voltage drop between the Source and the Drain normally will be 0.5 V, (less than 1 V) So the total voltage drop will be Vcc=2.7 V (laser diode) +0.5V (MOSFET) + (0.85A*0.5 Ohm) =3.6V. So, a single Li Ion battery (3.7V) is enough. As for MOSFET, you can use IRF540NF from Aliexpress, it is fairly cheep. Be careful, do not hurt your eyes from such a powerful laser. Wear a goggle in your project.
Nice explanation ❤
Więcej niż jedno zwierzę. 😅
So cute 🥰
Hi, how do you adjusted those constants ki, kp and kd for the PID?
Very nicely explained. Thank you.
great explanation....thank you for uploading such a useful video
Thank you very much
Are u using the same power to feed both motors?
Thank you very much
🎉
❤❤❤
哥们我还以为你是印度人哈哈
If 14 mA flows why the LEDs are not glowing? A LED will glow for as little as few 100 uA. Where is the simulation wrong?
Dear Nara49 Veera, Thank you very much for your comment. When I say that the circuit is no more working, when I_LED=14 mA, in the example, I mean the current was not kept the same as that flowing through a wire (no LED) or one LED, 41 mA. Ideal constant current source should keep the current constant no matter how many LEDs are there in series, always 41 mA, as in our example, but in reality such an ideal constant current source never exits, so It is necessary to tell how many LEDs can drive for a current source. We gave the formula in the video. In our example if the circuit gives 14 mA, (lower than 41 mA), we say that the source is no longer working, whether LED glowing or not is not relevant ! The key is that the current is out of control. Different LED has different properties, all we need is to supply the LEDs with controlled current I_LED. this is the circuit all about with formulas. Probably what you mean is that I should give a more realistic example with I_LED= a few 100 uA instead of 41 mA. If this is what you meant then you are totally correct. STEM Formulas
It is also interesting if you simply place a variable resistor to replace the LEDs in the circuit. When the resistance is zero, then the current through the resistor is 41 mA, when you increase the resistance of the resistor the current is kept at 41 mA for some time, when you increase further, the current drops. This is the usual behavior for a real life constant current source. Constant current source feels comfortable when the load is shorted, but it feels terrible when the load is open, R_load=∞, the voltage =I*R_load=∞, but the source does not have infinite voltage to supply! (whereas voltage source feels comfortable when the load is open, R_load=∞, but feels terrible if you short the output leads, in this case the current supposed to be infinite, but it can not deliver infinite current.)
@@stemformulas Then, perhaps, as the resistance increases beyond a limit, the current starts decreasing to support the supply voltage limitation. It is interesting. I will try to make a practical circuit when I get some time.
Did you have to write them small? Your accent is hard enough to understand too.
In real world application Ib != 0 (if you need some acurracy) and I would put second transistor in Darlington configuration to make Ib really small.
Good
Nice slow explaination, loved it so much!!! Thank you
Nice derivation.
I am trying to understand the potentiameter connection. Are pin 2 and 6 both along with a cap, all 3 is connected to the wiper and the cap is also grounded?
Where do I get 8V for Vi assuming it's ground is the same as the rest of the system?
Congratulations 🎉
So nice
I like how you coded the equations directly rather than use a PID library (I did that once myself long ago when I worked DCS company).
I am working on a video on PID algorithm (concepts behind the formulas and numerical examples with MATLAB).
Nice video. I would like to make one clarification though. At 5:32, approximating the base current with zero would indicate that the transistor is in cutoff mode and therefore I_0 would be 0 (because I_B*Hfe=I_0). So I don't think that is quite right. It seems the opposite to me, that I_LED == I when the transistor is open.
This is the exact circuit from my laser driver board I bought from Aliexpress 🤔
I am very glad to hear that. To find schematics from circuit boards is a very enjoyable and challenging task.
I don't think "clearly" would be the way I describe the video. Thorough? sure... Informative, educational? definitely. Clearly? Ehhh lol
Very nice. Whether you must repeat the 'Outline' again and again is another matter. We can look back, you know ;-)
Thanks thats a good!! But can u share ur coding?
Sir iss C ki value normalisation condition ko use krke kaise nikalenge
Could you please re-type your question clearly?
@@stemformulas How do we use the normalizations condition to find C? (Translated from Hindi)
Please watch the video "Normalization of eigenfunction of momentum operator" on STEM Formulas
@@JyotiRani-pt3tr thnx could you sir explain
Dear Jyoti Rani, Thank you very much for your message, I was wondering if you could tell me the names of textbooks about Quantum Mechanics you are using?
hi, can you provide the file of matlab code?