Resistor Sizes Vary Greatly?

[floobydust]

That text you quoted is decades old. You once again proved yourself wrong on your claims that new resistors are a conspiracy. How long are you going to keep making yourself a laughing stock? I mean, the credibility you have left is basically zero. Keep wrapping more tinfoil and keep providing zero evidence.

Once again, I have zero problems using moden high power density resistors significantly over 50% rated power. Other professionals agree. No proof of otherwise, not a single bad experience by a professional who actually designed this stuff in has been shown. The burden of proof is on who makes the claim, and extraordinary claims require extraordinary evidence.

50% derating suggestions hide some assumptions (e.g. PCB orientation, possible blockage of cooling, how close multiple heat-generating parts are close together, etc.). It's a rule to ease thermal design for those who don't have time or energy to think about it. There is no need to follow such practice if you understand thermal design and can simulate or practically measure the performance.

Exactly as with all other component types, manufacturer cannot predict how the customer uses the part and tests how it performs in isolation. Just like you can drive faster when there is no other traffic, and thus cars have higher top speeds rated compared to what you actually can drive at.

Credibility, reputation- I'm not here for that malarkey. In electronics a person is constantly wrong and only has more to learn.
Engineers that know it all and have a lot of ego crash and burn in the best ways. This is where you and I differ.

You've provided no formulas, calculations, datasheets, app notes, tech papers, URL's towards helping the thread, aside from urine.
Piss on me, piss on the thread but at least offer guidance for OP and the beginners here, or GTFO.

I see no way to reach out to Yageo to ask why they omit heat rise data for some of their acquired brands. FMP, PNP. So that OP would understand being ripped off.
I compared data on 65 different resistor makes/models including temp rise and physical (body) size, lead diameter etc. to see the game.
It's the 1/4-sized parts that I have issue with, as well as their deceptive datasheets.
Industrial products I design to 60°C ambient so a practical ball park dissipation number

Yageo Vitrohm POS series the 1/4W-body rated P₇₀ 1W is 130K/W and +200°C max. (which is more typical for wirewound).
Using 130K/W people here can do a little math and get a rosy estimate.

[Wil_Bloodworth]

I don't know how these can be equivalent.  The Chinese ones are even supposed to have a 5% tolerance.



- Wil

[wraper]

I don't know how these can be equivalent.  The Chinese ones are even supposed to have a 5% tolerance.

(Attachment Link)

- Wil

Of course they are not  . Small one is miniature, large one is not regular either but for high energy surges. As already told many times, power rating is not nearly the only thing that matters.

[Wil_Bloodworth]

Of course they are not  . Small one is miniature, large one is not regular either but for high energy surges. As already told many times, power rating is not nearly the only thing that matters.

Yes, I understand that.  I guess what I'm saying is that when I'm ordering resisters from DigiKey or Mouser, unless you just have a history of ordering that specific capacitor, there is no way to know what you're getting.  As far as I can see, there was nothing indicating that these were anything other than "normal" when ordering.  And you know... size always matters.

[ArdWar]

What are you even talking about? Both distributors include size/dimensions in their resistor table/data fields, and all reputable manufacturers provide datasheets for their products. The less common a product dimensions is, the more important its datasheet will be.

If you buy resistor without checking the data first or at least checking the corresponding product series then it's in you if you didn't get what you think you'll get.

[Wil_Bloodworth]

What are you even talking about? Both distributors include size/dimensions in their resistor table/data fields, and all reputable manufacturers provide datasheets for their products. The less common a product dimensions is, the more important its datasheet will be.

If you buy resistor without checking the data first or at least checking the corresponding product series then it's in you if you didn't get what you think you'll get.

I'm new to electronics so I don't know all that crap. No need to be a jerk.

And you guys do realize this was posted in the Beginners section don't you!!!

- Wil

[ArdWar]

I mean, you're the one claiming "no way to know" and "nothing indicating".

Another way to figure out albeit less reliable is when you find non beige/brown/blue axial resistor you're probably dealing with something "not normal"

[shapirus]

test them.

[Siwastaja]

Yes, I understand that.  I guess what I'm saying is that when I'm ordering resisters from DigiKey or Mouser, unless you just have a history of ordering that specific capacitor, there is no way to know what you're getting.

That's a wrong way to buy. Don't buy random parts based on quick parametric search; instead, take your time to look through the datasheet; calculate, simulate, measure, whatever is needed to qualify the part into your design - then buy, and confirm the suitability through prototypes. Then keep buying the same part number, so it doesn't matter where you buy it as long as it's a credible supplier and you don't get fakes.

[Siwastaja]

I'm new to electronics so I don't know all that crap.

That's OK. We are just reminding you about the fact that distributors like Digikey really do not exist for hobbyists (although they serve them as well). Component manufacturers make parts for professionals, to be used in production, and write their datasheets for professional design engineers. Hobbyists and beginners start working with many false assumptions and get surprised all the time, and that's fine; we all have been through that phase and I think it was fun; just remember you are the one who should be learning; don't turn into what floobydust became, a disgruntled hobbyist who decided so start a war against component giants because his own unwillingness to learn.

[Simon]

I mean, you're the one claiming "no way to know" and "nothing indicating".

Another way to figure out albeit less reliable is when you find non beige/brown/blue axial resistor you're probably dealing with something "not normal"

Green is usually an inductor

[wraper]

I mean, you're the one claiming "no way to know" and "nothing indicating".

Another way to figure out albeit less reliable is when you find non beige/brown/blue axial resistor you're probably dealing with something "not normal"

Green is usually an inductor

Only if it's glossy and somewhat different length and diameter proportions.

[Simon]

Yes typically 0.25W through hole inductors look like resistors but are greed, more than the gloss it's the bigger dip in the middle if I remember rightly, I guess it depends on value as it's probably the slot for windings that may be more or less filled.

The big give away is their very low resistance. When I was a kid I took one into my friendly TV repairer who explained why this perfectly healthy looking resistor had a wrong and very low resistance for it's markings.

[Gyro]

Green is usually an inductor

Flameproof resistors are normally Green, or Reddish Brown. The epoxy coating on inductors is shiny.

[tggzzz]

Of course they are not  . Small one is miniature, large one is not regular either but for high energy surges. As already told many times, power rating is not nearly the only thing that matters.

Yes, I understand that.  I guess what I'm saying is that when I'm ordering resisters from DigiKey or Mouser, unless you just have a history of ordering that specific capacitor, there is no way to know what you're getting.  As far as I can see, there was nothing indicating that these were anything other than "normal" when ordering.  And you know... size always matters.

When I started professional engineering, I too was "confused" by the variety of capacitors available. So I took the RS catalogue, and made a table showing the advantages and disadvantages of each type of capacitor. You might like to do the same; you will learn a lot.

Just wait until you wonder why some 10A fuses are a 5mm*20mm glass envelope, while other 10A fuses are 12mm*150mm and opaque (and marked 200,000A rms), and others are SMD.

You might "not have any way to know", but most people find the principal characteristics from the columns in the DigiKey (or Mouser/RS/etc) search results. Then, for the interesting devices, we can even use a more advanced technique: RTFDS, where DS is "Data Sheets"

On the bright side: you are a beginner, so ignorance is unsurprising and curable. None of that applies to some other prolific first posters on this forum.

[Siwastaja]

Also remember that the distributor information is sometimes just plain wrong. Some engineer there reads thousands of datasheets every day and quickly gathers the numbers. Mistakes happen. Always carefully cross-check part numbers between datasheet and what you are ordering, and carefully read the correct datasheet. At beginning this takes a lot of time but you'll get better at it.

[coppice]

When I started professional engineering, I too was "confused" by the variety of capacitors available. So I took the RS catalogue, and made a table showing the advantages and disadvantages of each type of capacitor. You might like to do the same; you will learn a lot.

There isn't a single capacitor type out there which doesn't have a mass of quirks. I haven't found anyone who thought this was well covered in their education. Its rather sad. You end up picking up things as you go along, from colleagues, data sheets and other snippets of knowledge, rather than a clear and complete comparison of current technologies.

[Siwastaja]

Indeed; if you can handle the different types and characteristics of real-world capacitors and inductors, then understanding power ratings and cooling of resistors should be easy-peasy.

[tggzzz]

When I started professional engineering, I too was "confused" by the variety of capacitors available. So I took the RS catalogue, and made a table showing the advantages and disadvantages of each type of capacitor. You might like to do the same; you will learn a lot.

There isn't a single capacitor type out there which doesn't have a mass of quirks. I haven't found anyone who thought this was well covered in their education. Its rather sad. You end up picking up things as you go along, from colleagues, data sheets and other snippets of knowledge, rather than a clear and complete comparison of current technologies.

I wouldn't want it well covered in education; there are far more fundamental topics that are more important.

That there are differences should be noted, with the details being understood when they become relevant.

[shapirus]

there is no way to know what you're getting.

Actually, today it's way easier to know that than ever. In the absolute majority of cases you can easily find any information very quickly on the internet. Part specs, typical circuits, questions and answers etc. Well, to be precise, it was easier some time ago, before the search results became flooded with tons of useless AI-generated crap, so today one needs to develop a better skill of filtering useful info from garbage than ever before.

Still, today versus the days before the internet became widespread is night and day difference. It was hard to get information back then. You were limited to what you could read in specialized magazines and in literature, not all of which were good at what they tried to do, especially where beginner-level things were concerned. Combined with the lack of, or very high price of equipment back then that one can get ridiculously cheap today, it really made it challenging for hobbyists and enthusiasts, and, above all, for kids. In my case, it was the reason why I quit the EE hobby in my early teens when I hit the barrier imposed by the (un)availability of information, parts, and equipment, and focused on computers instead, which at the time offered much broader opportunities to learn and achieve something. Now I revived this old hobby that I had abandoned, and I find it very satisfying to learn and do something when you have information and tools.

Going back to resistors, and other parts for that matter, datasheets are usually readily available in a couple of clicks and there's no difficulty whatsoever in reading them (and learning by understanding the parts that are new to you).

[coppice]

When I started professional engineering, I too was "confused" by the variety of capacitors available. So I took the RS catalogue, and made a table showing the advantages and disadvantages of each type of capacitor. You might like to do the same; you will learn a lot.

There isn't a single capacitor type out there which doesn't have a mass of quirks. I haven't found anyone who thought this was well covered in their education. Its rather sad. You end up picking up things as you go along, from colleagues, data sheets and other snippets of knowledge, rather than a clear and complete comparison of current technologies.

I wouldn't want it well covered in education; there are far more fundamental topics that are more important.

That there are differences should be noted, with the details being understood when they become relevant.

I think it justifies an hour or two of lectures. Engineers waste enormous amounts of time coming to terms with the fact that MLCCs aren't even close to being real capacitors, electrolytics have a bunch of funky issues, polarisation and absorption in some types of capacitors can be a problem, etc. Its one of those areas where you don't know what you don't know, so its hard to even formulate questions. If you've been primed then years later, when you have forgotten most of the details, you'll probably still remember that gotchas that lie in wait.

[tggzzz]

When I started professional engineering, I too was "confused" by the variety of capacitors available. So I took the RS catalogue, and made a table showing the advantages and disadvantages of each type of capacitor. You might like to do the same; you will learn a lot.

There isn't a single capacitor type out there which doesn't have a mass of quirks. I haven't found anyone who thought this was well covered in their education. Its rather sad. You end up picking up things as you go along, from colleagues, data sheets and other snippets of knowledge, rather than a clear and complete comparison of current technologies.

I wouldn't want it well covered in education; there are far more fundamental topics that are more important.

That there are differences should be noted, with the details being understood when they become relevant.

I think it justifies an hour or two of lectures. Engineers waste enormous amounts of time coming to terms with the fact that MLCCs aren't even close to being real capacitors, electrolytics have a bunch of funky issues, polarisation and absorption in some types of capacitors can be a problem, etc. Its one of those areas where you don't know what you don't know, so its hard to even formulate questions. If you've been primed then years later, when you have forgotten most of the details, you'll probably still remember that gotchas that lie in wait.

I'm in favour of making students realise that.you can't buy a resistor, but can buy something that is a combination of inductor plus capacitor plus resistor. Then do a little analysis to determine where typical poles and zeros will occur.

I'm not in favour of getting students to think too deeply about polystyrene caps advantages over teflon capacitors - except where it is critical to experimental apparatus they are using.

If you teach the characteristics of MLCC caps, what are you going to omit? What's the half-life of such knowledge? University should teach fundamentals that will last a lifetime. If they understand fundamentals, they will be applicable to whatever they encounter in the future. That won't happen with knowledge of the C-vs-V characteristics of CapCon's current products.

[Wil_Bloodworth]

I'm in favour of making students realise that.you can't buy a resistor, but can buy something that is a combination of inductor plus capacitor plus resistor. Then do a little analysis to determine where typical poles and zeros will occur.

I'm not in favour of getting students to think too deeply about polystyrene caps advantages over teflon capacitors - except where it is critical to experimental apparatus they are using.

If you teach the characteristics of MLCC caps, what are you going to omit? What's the half-life of such knowledge? University should teach fundamentals that will last a lifetime. If they understand fundamentals, they will be applicable to whatever they encounter in the future. That won't happen with knowledge of the C-vs-V characteristics of CapCon's current products.

I'm learning electronics at home in my living room in my spare time by myself without an instructor.  Unfortunately, the luxury of a teacher/mentor is not an option.

- Wil

[coppice]

I'm in favour of making students realise that.you can't buy a resistor, but can buy something that is a combination of inductor plus capacitor plus resistor. Then do a little analysis to determine where typical poles and zeros will occur.

I'm not in favour of getting students to think too deeply about polystyrene caps advantages over teflon capacitors - except where it is critical to experimental apparatus they are using.

If you teach the characteristics of MLCC caps, what are you going to omit? What's the half-life of such knowledge? University should teach fundamentals that will last a lifetime. If they understand fundamentals, they will be applicable to whatever they encounter in the future. That won't happen with knowledge of the C-vs-V characteristics of CapCon's current products.

A well balanced degree course teaches mostly strategic knowledge to keep you useful in the long term, sprinkled with a broadly useful mix of tactical knowledge to make you useful in the short term.
Things lots of people struggle with for many hours are excellent candidates for that tactical knowledge area, where they can be made useful in an hour or two.

[tggzzz]

I'm in favour of making students realise that.you can't buy a resistor, but can buy something that is a combination of inductor plus capacitor plus resistor. Then do a little analysis to determine where typical poles and zeros will occur.

I'm not in favour of getting students to think too deeply about polystyrene caps advantages over teflon capacitors - except where it is critical to experimental apparatus they are using.

If you teach the characteristics of MLCC caps, what are you going to omit? What's the half-life of such knowledge? University should teach fundamentals that will last a lifetime. If they understand fundamentals, they will be applicable to whatever they encounter in the future. That won't happen with knowledge of the C-vs-V characteristics of CapCon's current products.

I'm learning electronics at home in my living room in my spare time by myself without an instructor.  Unfortunately, the luxury of a teacher/mentor is not an option.

That doesn't change the point, of course.

I was in your position for a decade or so, before I became old enough to go to university. All I had available was a few magazines from newsagents, a few books from the local library, and my imagination.

Data books? No. The nearest was Towers International Transistor Selector.
Text books? No. Too expensive and specialised.
Instead we learned to scavenge any information we could find, and more over it to extract everything it contained.
Now the issue is to quickly determine what to ignore - the polar opposite.

I made many mistakes and planned how to make only new mistakes:)