The purpose of the op is NOT to get a circuit to work. I think it's about studying the minutia that never becomes significant in a real circuit.

No, it's to expand understanding, and to have fun exploring the nature of the these devices.

To a technician, this is unnatural idea. Many engineers too. A parameter that has no real use, is not stable, is anathema to designing.

Agreed. I would never use that other perspective in designing, but it was just the best way for me to understand the device at the time (and it still kinda is).


Overall, you guys need to get it out of your head that EVERYTHING needs to have immediate consequences for a real-life circuit. This is a HOBBY site, we don't need to be trained to be the most efficient designers, we're allowed to experiment and play. Toying with concepts, models, and systems is my favorite thing to do, so I do it most.

 

<snip>
Overall, you guys need to get it out of your head that EVERYTHING needs to have immediate consequences for a real-life circuit. This is a HOBBY site, we don't need to be trained to be the most efficient designers, we're allowed to experiment and play. Toying with concepts, models, and systems is my favorite thing to do, so I do it most.

Perhaps you need to understand that you will not go far chasing shadows, and focus on the real. You keep hearing people tell you it doesn't help, it doesn't. It doesn't even really help understanding, it is a distraction.

I love concept circuits, even if they do nothing. I love SciFi, because it introduces me to new ideas. I don't like wasting my time on things that will get me now where.

I mentioned a real application for resistance in diodes, but it does not apply to LEDs (nor will it ever). Did you pick up on what it was? Trivia has its place, but this goes beyond that. In trying to design project, it is of negative value, too many beginners try to use a voltage source to control a LED with nothing but negative consequences, when they could be using the same time constructively achieving their goal.

I hear the phrase thinking outside the box a lot, especially with fruitless endeavors like over unity. Fantasy has its place, but it should not be confused with science. Some models approach fantasy, it is important to recognize when this is the case.

 

Perhaps you need to understand that you will not go far chasing shadows, and focus on the real. You keep hearing people tell you it doesn't help, it doesn't. It doesn't even really help understanding, it is a distraction.

I love concept circuits, even if they do nothing. I love SciFi, because it introduces me to new ideas. I don't like wasting my time on things that will get me now where.

I mentioned a real application for resistance in diodes, but it does not apply to LEDs (nor will it ever). Did you pick up on what it was? Trivia has its place, but this goes beyond that. In trying to design project, it is of negative value, too many beginners try to use a voltage source to control a LED with nothing but negative consequences, when they could be using the same time constructively achieving their goal.

I hear the phrase thinking outside the box a lot, especially with fruitless endeavors like over unity. Fantasy has its place, but it should not be confused with science. Some models approach fantasy, it is important to recognize when this is the case.

I really like the last part there, about over-unity and fantasy. I agree completely. I don't think I'm approaching that at all, I've kept a realistic mind.

 

It is not realistic to control LED brightness via voltage. It really is that simple.

It could be done with lot of control circuitry, that might not work, or you can use a simple resistor and a different theory.

Theory is important. I have found the same circuit called half a dozen different things, and looked at different ways to achieve results. It is the results that truly matter. How you approach a problem really matters.

 

I really like the last part there, about over-unity and fantasy. I agree completely. I don't think I'm approaching that at all, I've kept a realistic mind.

The reality in the design of projects you have to prove the standard method wrong before questioning its validity. If
you cannot then in practical terms it is pointless

 

I've found now that this is a much better approximation than I previously thought, however, because you can just adjust Vf for the current you're aiming for. So, if you're aiming for 20 mA with a 9V source, and the Vf at that point is 2V, you can do the whole (9-2)/Ω=20mA thing and be good. AND, if you wanted to aim for 5mA instead, you'd find the Vf at that point, say it's 1.9V, you can do the math differently (9-1.9)/Ω=5mA, and you'll be able to calculate the resistor more accurately than you would be able to assuming Vf is constant. It's a small change, but I'm very excited that the rule can be made more "general", because not all diodes are LEDs, and some require a good range of currents and accuracy.

Why don't you understand that the Vf is a range of numbers and is not a single number?? It even changes when the temperature changes.
Each LED has a different Vf. If you feed it a current then it works fine.

Go to your electronics parts distibutor and ask for an LED with a forward voltage of 1.85V. They will laugh at you and say, "Here is a red one and here is its datasheet. Measure its forward voltage yourself".

If you use a series current-limiting resistor and a higher supply voltage then the LED will be fine.

 

"anathema": a thing that is detested or reviled.
I haven't heard that word for so long that I had to look it up!
I learn something almost every day on this site
I'm going to change my signature line to include that.

Now, what's the word for having fun by persuing the minutia of counter- productive theories? Mental masturbation?

Better yet, what is the word for using up other people's time and website space to to that?

 

Now, what's the word for having fun by persuing the minutia of counter- productive theories? Mental masturbation?

My boss used to think it was my job...... I spent so many years listening to idiots trying to repeal the laws of physics. Most of them worked in marketing, the rest were customers.

FRUSTRATION (noun, def) the physical stress that results from not being able to choke the life out of the idiot who is tormenting you.

 

The reality in the design of projects you have to prove the standard method wrong before questioning its validity. If
you cannot then in practical terms it is pointless

I never claimed the standard is wrong, quite the opposite actually, I've come to like it even more after this thread.

 

Why don't you understand that the Vf is a range of numbers and is not a single number?? It even changes when the temperature changes.
Each LED has a different Vf. If you feed it a current then it works fine.

Go to your electronics parts distibutor and ask for an LED with a forward voltage of 1.85V. They will laugh at you and say, "Here is a red one and here is its datasheet. Measure its forward voltage yourself".

If you use a series current-limiting resistor and a higher supply voltage then the LED will be fine.

I understand that Vf is variable, completely. Look at the post you quoted. I made it pretty obvious that I understood that Vf changes with current (or vice versa, if you wanted).

 

My boss used to think it was my job...... I spent so many years listening to idiots trying to repeal the laws of physics. Most of them worked in marketing, the rest were customers.

FRUSTRATION (noun, def) the physical stress that results from not being able to choke the life out of the idiot who is tormenting you.

Repeal the laws of physics? Who here's trying to do that? Everything I've said has been completely valid, and within the laws of physics. Everything people have been complaining about is completely unwarranted, as they've automatically assumed things about me to be true that aren't. You can take an LED, find the current, and calculate it's Vf from that, OR you can force a Vf, and find the current from that. Period. You can't argue against that. I know it's not a good idea practically, as I've made extremely obvious several times, but it's not outright wrong. If you don't understand that, then you don't understand basic algebra, and relationships between variables.

 

"anathema": a thing that is detested or reviled.
I haven't heard that word for so long that I had to look it up!
I learn something almost every day on this site
I'm going to change my signature line to include that.

Now, what's the word for having fun by persuing the minutia of counter- productive theories? Mental masturbation?

Better yet, what is the word for using up other people's time and website space to to that?

If you detest a simple algebraic relationships, sorry, your life is going to be hell.

What I've done isn't counter-productive at all. I've learned about an entire branch of mathematics, and I've learned how to use load-lines much better since I've started experimenting with all of this.
It's not a theory, either, and I haven't had to pursue it long, it was just something I noticed in the back of my head long ago, a thought that I wanted to share.

If anything, I'm not wasting other peoples time, but it's the other way around by now. I've had to say the same thing over and over again, and listen to people rant and complain about things that I deliberately addressed already. "Oh, LEDs are current-controlled, if you use a voltage source with an LED, it will go boom, lol" Seriously, are people even reading what I'm saying? If you're getting tired of my long posts, then STOP forcing me to say the same things over and over again, and read them the first time I post them.

Honestly, we need to get someone to come in and set all of this straight. I'm not a raving lunatic who doesn't know what he's talking about, who's trying to act smart by posting bullshit ideas. Seriously, this all started with a simple comment, something like "Technically, LEDs react to both voltage and current simultaneously". Voltage and current are directly related, and, therefor, you're forced to control both at the same time, even if you're trying to only control one, automatically. Simple concept, but it spawned enormous bitching, and for really no reason. All the whining has been about things I've already addressed. Blows my mind, really.

 

You do not control the voltage of an LED, it sets its own voltage. You simply set its current.

 

You do not control the voltage of an LED, it sets its own voltage. You simply set its current.

Agreed. No rational person could even dispute what you just said. The only caveat I issue to all reading this is that when driving one or more LED lamps with a current source or voltage source plus resistor, is that the said source can meet the maximum forward voltage drop of all the devices in the series string. Other than that we need not get too involved in what is happening with the Vf parameter.

Claude

 

You do not control the voltage of an LED, it sets its own voltage. You simply set its current.

Agreed. No rational person could even dispute what you just said. The only caveat I issue to all reading this is that when driving one or more LED lamps with a current source or voltage source plus resistor, is that the said source can meet the maximum forward voltage drop of all the devices in the series string. Other than that we need not get too involved in what is happening with the Vf parameter.

Claude

You are both correct in that, in practice, you're really just trying to focus on current, and keeping it controlled. Voltage sort of takes care of itself it seems. However, when you control current, you're controlling voltage in some way, knowingly or not. That's what's happening when Vf "takes care of itself". Now, earlier in this conversation, it was said that this was just assumed to be true, but it seems like there's still some confusion about that, so I have explicitly stated it for clarity.
I'll maybe have to make a video showing the in-depth operation of series-diode circuit characteristics. It's all about visualizing the load-line.

 

You are both correct in that, in practice, you're really just trying to focus on current, and keeping it controlled. Voltage sort of takes care of itself it seems. However, when you control current, you're controlling voltage in some way, knowingly or not. That's what's happening when Vf "takes care of itself". Now, earlier in this conversation, it was said that this was just assumed to be true, but it seems like there's still some confusion about that, so I have explicitly stated it for clarity.
I'll maybe have to make a video showing the in-depth operation of series-diode circuit characteristics. It's all about visualizing the load-line.

Well thanks Austin, if that is something you would like to do, who am I to dissuade you? You impress me as an intelligent person, but I wonder if that feeling is reciprocated. From what they've posted thus far, I believe all in this thread have a good understanding of load line characteristics & computational methods.

I believe all in this thread are intimately familiar with Shockley's diode equation, & Ohm's law, the 2 combining into a load line relationship. My summary is that we know more than you think we know. I'm not questioning your ability, but I get the impression that you are of the belief that we need "enlightened" re load line & related LED issues.

From what I've seen in this thread, the people here have a pretty solid understanding of LED operation, as well as how to drive them electronically. I doubt that your proposed video would teach us anything new. Again, I'm not questioning your ability, but rather, it seems that you are not too impressed with ours.

I don't mean to sound defensive, but I have studied LED lamps & many semiconductor properties since the 70's, practiced EE R&D since then, am now in the last stage of my Ph.D., so I've been there & done that. Things like Shockley equation & load lines are pretty old hat. I believe the others would concur.

But if making such a video is your desire, like I said, who am I to dissuade you from doing so? Best regards.

Claude

 

Well thanks Austin, if that is something you would like to do, who am I to dissuade you? You impress me as an intelligent person, but I wonder if that feeling is reciprocated. From what they've posted thus far, I believe all in this thread have a good understanding of load line characteristics & computational methods.

I believe all in this thread are intimately familiar with Shockley's diode equation, & Ohm's law, the 2 combining into a load line relationship. My summary is that we know more than you think we know. I'm not questioning your ability, but I get the impression that you are of the belief that we need "enlightened" re load line & related LED issues.

From what I've seen in this thread, the people here have a pretty solid understanding of LED operation, as well as how to drive them electronically. I doubt that your proposed video would teach us anything new. Again, I'm not questioning your ability, but rather, it seems that you are not too impressed with ours.

I don't mean to sound defensive, but I have studied LED lamps & many semiconductor properties since the 70's, practiced EE R&D since then, am now in the last stage of my Ph.D., so I've been there & done that. Things like Shockley equation & load lines are pretty old hat. I believe the others would concur.

But if making such a video is your desire, like I said, who am I to dissuade you from doing so? Best regards.

Claude

I understand what you're saying, and thank you. I don't question anyone's intelligence or understanding (I am still learning here, after all), but, if anything, their approach to the issue. I think I get why everyone was so quick and harsh, but it really didn't help me or anyone else who may stumble onto this thread. If I did ever make a video, you may not learn anything, but it would still be helpful for others, and could still possibly better explain myself. I think I was really just getting frustrated because I felt like people didn't seem to get what I was saying, and that I was losing some sort of credibility.

 

Repeal the laws of physics? Who here's trying to do that? Everything I've said has been completely valid, and within the laws of physics. Everything people have been complaining about is completely unwarranted, as they've automatically assumed things about me to be true that aren't. You can take an LED, find the current, and calculate it's Vf from that, OR you can force a Vf

and kill the LED in the process. I think the point of this thread was summed up pretty succinctly as "mental masturbation" which is to say endlessly debating something that is useless.

If you read your posts, it appears you think you have "discovered something" and are hell bent on defending your discovery.

What you have discovered is the way to blow up LEDs. Some of us don't find great intellectual value in that.

 

and kill the LED in the process. I think the point of this thread was summed up pretty succinctly as "mental masturbation" which is to say endlessly debating something that is useless.

If you read your posts, it appears you think you have "discovered something" and are hell bent on defending your discovery.

What you have discovered is the way to blow up LEDs. Some of us don't find great intellectual value in that.

At this point, It's almost like you're trolling.
Yes, running an LED on a constant voltage source is bad practice. Wow. I haven't said that a dozen times already or anything. Literally the only thing I wanted to make clear is that, in the end, voltage and current are related, and no matter what, when you control one you control the other. This is ohms law, basic electronics, basic algebra, basic concept. Simple simple simple. I was literally told earlier that this was self-evident, but you're proof that it isn't. Looking at driving LEDs with A SERIES RESISTOR in terms of voltage is perfectly valid mathematically and conceptually.

I haven't discovered anything new, I know that, that's obvious. I've made an observation, that's it.

What I've found is a way to look at the problem. Like looking at addition in terms of subtraction. Yeah, it might not make a difference in the end, but it can be enlightening, or, at the very least, interesting. It's NOT useless if you gain insight.

I'm just glad there are a few here who actually get what I'm saying. I'm honestly starting to become embarrassed in these responses. This forum can, and does, do a lot better than this.

 

At this point, It's almost like you're trolling.
Yes, running an LED on a constant voltage source is bad practice. Wow. I haven't said that a dozen times already or anything. Literally the only thing I wanted to make clear is that, in the end, voltage and current are related, and no matter what, when you control one you control the other. This is ohms law, basic electronics, basic algebra, basic concept. Simple simple simple. I was literally told earlier that this was self-evident, but you're proof that it isn't. Looking at driving LEDs with A SERIES RESISTOR in terms of voltage is perfectly valid mathematically and conceptually.

I haven't discovered anything new, I know that, that's obvious. I've made an observation, that's it.

What I've found is a way to look at the problem. Like looking at addition in terms of subtraction. Yeah, it might not make a difference in the end, but it can be enlightening, or, at the very least, interesting. It's NOT useless if you gain insight.

I'm just glad there are a few here who actually get what I'm saying. I'm honestly starting to become embarrassed in these responses. This forum can, and does, do a lot better than this.

And Austin, I'd like to say that we've said that a dozen times already. Like I said before, this is much ado over nothing. I always drive an LED string (the number of lamps in the string may be just 1, or 3, or 6, or more) with a constant current source, or a voltage source plus an adequate series resistor.

In addition to computing the forward current in the string, I always compute the forward voltage as well. It's all important to know this. If I'm using a +12V source with series resistor, or current mirror/source/sink, to drive a string of 6 lamps, I need the Vf parameter. If the lamps are infrared w/ 1.50V maximum Vf, I can make it with a current source or current drive buck converter since 6 X 1.5V = 9V < 12V supply. But if the lamps are amber w/ a Vf of 2.2V, the string of 6 drops 13.2V, & forget it.

Nobody here is unaware of that. I'll bet every person in this thread that debated you is well aware of the importance of Vf & that it is intimately related to If. We live in an age where education is attainable by vast numbers of people from all backgrounds. This isn't 1840 when only kids from a well to do family could go to college. People dirt poor attended college with me back in the 1970's, some graduated & got good jobs.

Unless one is employed doing leading edge research, it is not likely that what that person knows is limited to just him. I worked for 11 years in currency validation. When you insert a $1 or $5 dollar bill into a vending machine, I developed the hardware that optically & magnetically scanned the currency, determined authenticity, & denomination, up to $100 bills, as well as 90 or so different countries.

My work put me in a position where I had nobody to lean on for help. My rivals who made this same kind of product did not & still do not publish their methods & neither did we. It's a trade secret. So I had to spend countless hours working in the lab studying money properties, scanning them optically & magnetically, & observing which parameters are worth exploring & which are not.

A lot of conventional wisdom assumptions are proven wrong. My point is that because I worked in an area that is trade secret protected, I acquired knowledge that few people in the world possess. When I left the company I was informed that if I go to work for a rival, the use of anything I learned there could result in a law suit. All departing personnel were issued this notice.

Anyway, info such as that is something I have that few others have in this world, & I am honor bound not to divulge it, as well as legally liable. But info such as how LED's work, how they best are driven, etc., is hardly a secret, just like Ohm's law, Shockley's diode equation, etc. I cannot understand how anyone would lecture people who have years of experience practicing the art, as well as lots of formal education in the same, thinking that they are telling us something new.

I'm sure you mean well, but believe me when I say that this is nothing new to us. Those who posted on this thread obviously know how to drive an LED(s) & they are certainly aware that If & Vf are inter-related in a strong sense. This stuff is taught at the undergrad level. The number of people w/ college degrees these days is staggering. I read that 90% of all scientists/engineers who ever lived, are alive today! That tells us something.

To get on a platform & lecture on electronics requires a Ph.D., or at the very least an MS plus lots of experience in the art. I've been doing this 34 yrs., in my dissertation stage of Ph.D., & most of what I post is well known already. When I graduated with the BE in the late 70's, I remember being told that holding a BE (or BS) just doesn't have the power it had a generation earlier, that an MS is the minimum if one wishes to stand out.

How true then, even more so now. Please reread your posting comments & you should see what I mean. Your points made are very well known to any practitioner with a BS (or BE) in full EE, & 5 or more years practicing actual hardware design. LED lamps are not a mystery, they weren't so even in the 70's when I studied EE. The diode properties & If/Vf relations, were old news in the 70's. I learned the way to drive a p-n junction around 1975 or so in electronics lab, 1st course. The Vf/If puzzled me during 1 week of the course, then I learned it, & have had no doubts since.

Sorry to run on, BR.

Claude