I think it’s fair to say that the humble resistor is one of the first electronic components that most members of the EETimes community would have come across. Certainly this was true in my day: Ohm’s law was one of the first things in any electronics textbook. Even in these days of easy-to-use microcontrollers (MCUs), anyone who wants to drive an LED using an MCU pin needs to know about resistors and Ohm’s law to avoid a dead LED or — worse still — letting the magic smoke out of the MCU. Pretty much anyone who is reading this will know about Ohm’s law, so I’m not going to go into that here. (There are lots of tutorials on the Internet if you need to bone up on it.)

So, how have resistors evolved over the years? I was brought up and grew interested in electronics at the end of the valve (vacuum tube) era. Resistors at that time were huge in comparison to today’s tiny components, and if there was a tolerance at all it was likely to be 10%. Resistors that went high or open circuit for no apparent reason were not uncommon — they were made of compressed carbon in a tube.

As an aside, early telephone microphones were made with carbon granules that were alternately compressed and released by a diaphragm, varying their resistance according to the impinging sound waves. These granules sometimes got “packed,” which caused one’s speech to sound truly horrible. Banging the headset on the table loosened them and gave a temporary respite, but we digress.

These days, resistors are more likely to be metal-film types. A metal film is printed or deposited — usually in a spiral — on a ceramic tube, which is then connected to wires, sealed with a tough coating, and marked. In the case of small surface-mount resistors, it is a zig-zag of film on a square block of ceramic. Laser trimming is sometimes used to get precise values. For higher-power types, resistance wire is wound on a tube, but more on these later.

Showing some tolerance As the late great Bob Pease would say: “What’s all this tolerance stuff, anyhow?” In the early days, resistors could not be made to very precise values, so they were given a tolerance. If a resistor had a nominal value of 1,000Ω and a tolerance of 10%, it could be anywhere between 1,000Ω +/- 10% of that value (i.e., 1,000Ω +/- 100Ω, or anywhere between 900Ω and 1,100Ω).

If you needed a precise value — say 965Ω — you had two choices; either you went through a bunch of 1,000Ω resistors until you found one sufficiently close to the desired value, or you could pay more and get a resistor that the manufacturer had measured and marked to a near value. This cost the manufacturers and hence you, the customer, more. But in the old days of valve circuitry, values were not that important, and resistors with a 10% or even 20% tolerance were usually considered adequate.

Thus it was that the resistor “series” were born. The first series was the E3. I don’t know where the E came from, but the 3 means there were 3 values — in this case, 100Ω, 220Ω, and 470Ω, along with their multiples and submultiples of 10 for each decade of values (e.g., 10Ω, 100Ω, 1KΩ, 10KΩ 100KΩ, and 1MΩ). Where did these values come from? Well, the E3 resistors had a +/- 50% tolerance (yes, really!) so your 100Ω resistor could be anywhere from 50Ω to 150Ω. Now the next value up, 220Ω, could be anywhere from 110Ω to 330Ω, so there was a bit of overlap. This was useful if you needed to find a certain value, but not if your circuit was sensitive to the value you put into it.

By the time I started getting interested in these things, the 50% resistors in the E3 series were no longer with us, and 20% resistors, in the form of the E6 series, were on their way out also. The E6 values were 100Ω, 150Ω, 220Ω, 330Ω, 470Ω, and 680Ω, along with their decade counterparts. These were soon supplanted by 10% resistors in the E12 series: 100Ω, 120Ω, 150Ω, 180Ω, 220Ω, 270Ω, 330Ω, 390Ω, 470Ω, 560Ω, 680Ω, and 820Ω (and their decade counterparts, of course). These are known in the trade as “preferred” values in that, if you are designing, it is preferred that you use these values because they are easy to obtain! You can perform the calculations on these values and find there is still a little overlap. In fact, thanks to Excel, I have done this for the E12 series for you as illustrated below:

As you can see, the theoretical limits of each value overlap, except if you wanted a 242.5Ω resistor. You might find a 242Ω or a 243Ω, but that is the nearest you would get!

The E12 series, in turn, gave way to the E24 series with 5% tolerance, the E48 series with 2% tolerance, the E96 series with 1% tolerance, and the E196 series with 0.5% and better tolerance. But really, the values you see most often are the E12 values. If you want to see how the resistor series relate to each other there is a nice diagram here.

David Ashton is not entirely sure what he is. He was born in London, England. He was raised, trained, and worked in Rhodesia (now known as Zimbabwe) and now lives in Australia. Based on this, he describes himself as a Pom-Rhodie-Zimbo-Aussie. Workwise, things are much the same. He has run electronics labs and managed telecommunications centers. He has run his own communications business, and he is now working as a telecom specialist keeping a large communications network up and running. In his own words: "I'm a jack of all trades and, yes, I admit that I'm the master of none, but I kind of like it that way because it makes it difficult to get bored." 

David Ashton is not entirely sure what he is. He was born in London, England. He was raised, trained, and worked in Rhodesia (now known as Zimbabwe) and now lives in Australia. Based on this, he describes himself as a Pom-Rhodie-Zimbo-Aussie. Workwise, things are much the same. He has run electronics labs and managed telecommunications centers. He has run his own communications business, and he is now working as a telecom specialist keeping a large communications network up and running. In his own words: "I'm a jack of all trades and, yes, I admit that I'm the master of none, but I kind of like it that way because it makes it difficult to get bored." 

If you needed a precise value -- say 965Ω -- you had two choices; either you went through a bunch of 1,000Ω resistors until you found one sufficiently close to the desired value, or you could pay more and get a resistor that the manufacturer had measured and marked to a near value.

I used to trim carbon composistion resistors by choosing a value below the target value and then carefully filing into the body (effectively reducing the cross section) to get the exact resistance.

@David: This is a great column -- very interesting -- I'd completely forgotten what a zero-ohm resistor was used for.

One question is when you say "I have seen 50 ohm and 600 ohm resistors -- which are of course common impedances -- on circuit boards, and they stuck out like sore thumbs."

Why do you say these are "common"? I would have thought they would not be common at all. 

@antedeluvian: I used to trim carbon composistion resistors by choosing a value below the target value and then carefully filing into the body (effectively reducing the cross section) to get the exact resistance .

To this end, I employed Excel to work out the values of any combination of two resistors in the same decade and in adjacent decades, and I always keep this spreadsheet handy. For example, it tells me that if I need a 900KΩ resistor for a decade voltage divider, I can realize this using a 220KΩ resistor and a 680KOmega; resistor in series.

I always love it when Excel is applied to electronics. I am sure you remember my blog on Planet Analog that allwoed you to calculate the nearest you could get to a value determined by the ratio of two resistors. See "Excel-Optimizing Resistor Ratios" part 1 and part 2.

If you needed a precise value -- say 965Ω -- you had two choices; either you went through a bunch of 1,000Ω resistors until you found one sufficiently close to the desired value, or you could pay more and get a resistor

Of course you could always use a potentiometer or a resistor and potentiometer. See my blogs on Planet Analog "Potentiometers: Mechanical & Electronic" Part 1 and Part 2

As EETimes community member Antedeluvian pointed out in a comment recently, 1% 1/4W resistors are the same size as 5% 1/2W resistors. If the 1% resistors dissipated 1/2W, they would probably do so quite safely, but their value might go outside the 1% tolerance. You can get through-hole 1/10W resistors that are only a tenth of an inch long, and SMD resistors that are even smaller, right up to big wire-wound versions capable of dissipating 50W or more.

A good rule of thumb is to specify your resistors for at least double the power they will need to dissipate if you can. A resistor run at, or near, its power rating may do so quite safely, but if it is attached to a printed circuit board (PCB) it may become hot enough to burn out the board or melt the solder and cause dry joints. If you're using wired components, mount them as high off the board as you can -- and even put a turn of wire in the leads -- so they get the maximum possible air flow for cooling. Some resistors have their own finned heatsinks, and you can bolt these to a chassis or a larger heatsink to dissipate the heat.

Sage advice. The post that I made triggered a blog on a similar topic on Planet Analog "Power Dissipation: My Arch-Nemesis

If you needed a precise value -- say 965Ω

Interesting article.  Or arrange 2 or 3 0.1% resistors in series/parallel.  This also lets you tweak the value precisely by hand-picking if you are trying to balance a pair of resistances, say for an instrumentation amplifier.

As for unusual resistors, the Heathkit Co used to sell a large 50 ohm non-inductive resistor (I think it was a film type) on a 5" x 0.75" hollow ceramic core that mounted inside a gallon paint can filled with transformer oil for cooling.  It was called The Cantenna, and was used as a dummy load for testing kilowatt RF amplifiers for brief periods, as long as one allowed time for cooling off between zaps.  There are several currently listed on ebay.

If a ham operator did not have a Cantenna or equivalent, an incandescent light bulb did the trick, but not as precisely.

Somthing else to consider when using a resistor is the voltage rating. This is over and above the power rating. You could have a high voltage and a low current and be within the power rating, but the voltage would arc from one side to the other completely nullifying the resistance.

Associated with that is the voltage surge that the can flash across tyhe resistor as well. We often use a series resitor to and input ahead of a TVS or MOV in order to limit the current. The best was a 1/2W carbon composition resistor (not carbon film, a deposition of carbon on a glass tube) for higher values/ At about 10R the 1/4W was fine, but at 100R the rersistor would crack under surge conditions. We still use the through hole resistors with SMD.

The original Allen Bradley line appears to have been taken over by Newark/Element14 as their Multicomp MCRC line of resistors.

There are other resistors rated for surge conditions- I must admit I haven't tried most of the newer ones, sticking with the tried and true.

A more interesting post than one would expect! One correction, though: The prefix for 'thousand' (kilo) is lower-case 'k', not 'K' which is reserved for temperature. In other news, here is a hodgepodge of comments: On a Windows PC, with 'NumLock ON', hold 'Alt' down and press numeric keypad '2' then '3' then '4' and let up 'Alt': Ω; Alt+230 gives µ and Alt+130 é. There are other useful ones too (good-luck finding them, or a list! [most chars require four numerals]). I once was in a situation where circuit precision needed to be increased. The EE simply scratched-out all the '5%' tolerances and changed them to '1%'. That was bad, very very bad: not all the values on the E48 table appear on the E96 table, so a bunch of expensive 'non-standard' values were about to be ordered (but you KNOW the manufacturers do actually make them, just so they can profit from such oversights). I made a spreadsheet macro to convert resistances+tolerances to 'closest standard values' to save the day. (It also did linear interpolation and found the best two-value series or parallel combination if invoked under a different name.) 1/4W resistors all come with the same voltage rating. How can you have 1/4W in a 1MΩ resistor? What IS a 1/4W 0Ω resistor? Lots of Mil-Spec resistors the size of commercial 1/4W ones were marked alphanumerically; it was a matter of pride to install them so that all the designations were visible and oriented the same way. The code was rather clever too, and is being used more and more outside that application. '1403' just meant 140E3, but 14R3 meant 14.3, just as many modern commercial designs have '3V3' supply rails. As I mentioned in the thread elsewhere on potentiometers, if you have a 'tapped' resistor (many wire-wound power-resistors have exposed elements and a clamp-on 'third terminal'), then the wattage-rating has to be divided by the same ratio as the used part of the element. And so on....

Oh, and how the heck do I make line-breaks on this site? I have whole sequences of CR LF in the above....

In addition to being used to jump tracks on a single layer board, zero Ohm resistors are also used to enable one of several configurations of a board at assembly time. Say for instance you had a board with several different memory options. You could use selectively installed zero Ohm resistors to select which option is installed. I've also been known to put zero ohm resistors in places where I might want a series resistor...

@Max...  "One question is when you say "I have seen 50 ohm and 600 ohm resistors -- which are of course common impedances -- on circuit boards, and they stuck out like sore thumbs." "Why do you say these are "common"? I would have thought they would not be common at all. "

They are common IMPEDANCES, but  NOT preferred values.  It is most uncommon to see a 50 or 600 Ohm resistor on a board.  They are made, for obvious reasons, but to see their color code on a board is unusual, and being an unusual combination of colors, to me they jump out at you like a badly-spelled word.

@Antedeluvian Somthing else to consider when using a resistor is the voltage rating.

Good point, especially with that tiny gap in laser-trimmed surface mount resistors.

A junior engineer once designed a T1 repeater for me and used surface mount resistors in the line buildout pads (attenuators).  They were well within their ratings under normal operation, but the power was a 60 mA "phantom" current source that sent DC over the twisted pairs through the transformer center taps. 

What neither of us realized was that the power source had a large electrolytic capacitor in its output.  When the current loop is open the power source rises to +-130V (260V total between the pairs) as it tops out trying to maintain a constant 60mA current.  Plugging in the connector from this power source to the DUT applied the full 260V to the resistors because the capacitor took a long time to discharge.  Of course the resistors burned up everytime we plugged in the connector with the power source already turned on.

We had to respin the pcb for other reasons; this time we used good old large axial leaded resistors with lots of thermal mass.

@GSKrasle.. "A more interesting post than one would expect!"

Thanks for that.... while writing this I rediscovered what a huge subject this is!  As I remarked, I'm only scratching the surface.

Re k not K, very true, but just writing resistor values you'd usually write 3K3 rather than 3k3 which is as you say technically correct. 

Getting Ohms symbol - the Alt way works as well as Symbol-font W.  One thing I have always found annoying is that in Excel or Basic CHAR (234) does not give you the same symbols as ALT-234.  Grrr...

> it was a matter of pride to install them so that all the designations were visible and oriented the same way

One mentor I had used to insist on this with color code resistors - the gold bands were always the same way.  I still do that to this day.

In my younger days I have come unstuck assuming that the power rating of a petentiometer still applied if you were only using part of the pot.  An expensive (and smoky) lesson!

> Oh, and how the heck do I make line-breaks on this site?

Some people just don't seem to be able to.  I'd suggest using a different browser - that sometimes seems to work, but I suspect there is something in your PC setting somewhere that is only putting a CR or an LF in your text, not both, or something....

@Antedeluvian, thanks for all the comments, and I thought several times when writing this that you ought to be doing it!  You've filled in a few gaps I think.

Excel is so handy for things like this, and I knew you'd appreciate the use of it!  Between you and a lady we have at work who's also an Excel whiz, I have learned heaps.

@ David it is most uncommon to see a 50 or 600 Ohm resistor on a board.

Just a couple weeks ago had to replace a 600 ohm wirewound 10 watt resistor, was high by about 8 ohms and the DUT power-on self test complained about it.

Normally when I need 50 ohms I settle for a standard 49R9.  But when trying to get 450 ohms to make a 10:1 scope probe nobody stocks these.  Did find one place online that claimed they had them, but when they arrived they were 470 ohms, not 450.

There are many precision through hole resistors with their values printed instead of colour bands.  These are most annoying; they are usually positioned text-down against the pcb and cannot be read.

@Zeeglen... "If a ham operator did not have a Cantenna or equivalent, an incandescent light bulb did the trick, but not as precisely."

In my first job as a radio tech, I made a dummy load from an auto 10W 12V bulb soldered to a PL-259 connector.  Worked a treat, these were the days of AM, so you could check your modulation as well!  The SWR was not bad at 40 MHz.

In a later job I did the same for 80 MHz radios, but they needed a small trimmer cap in parallel to trim out the inductance of the bulb.  And these were FM sets so you could not see the modulation.  But the company I worked for then had a test bench which had 3 or 4 radios on alternate Tx / Rx "soak test" tying up our dummy loads, so the bulbs were great, apart from freeing up the expensive dummy loads they gave a clear indication that the radio was working.

@David An expensive (and smoky) lesson!

Did that once too, tried to make a light dimmer with a volume control salvaged from a scrapped radio.  Wasn't expensive, but was sure smoky when used on 120VAC.

As for k, K, m and M, avoid M or m for large value resistors if using LTspice simulation.  It interprets both m and M as "milli"; the  terminology is "meg" as in "1 meg".  "1 M" is a milliohm.

David wrote: Getting Ohms symbol - the Alt way works as well as Symbol-font W.

I've occasionally seen data sheets where they screwed up and forgot to change W to the Symbol font -- or maybe the Symbol font wasn't installed.  So the sheet recommends a 10KW resistor instead of 10KOhm.  Those 10KW resistors must be gigantic!

@Zeeglen.... "But when trying to get 450 ohms to make a 10:1 scope probe..."

Well from my spreadsheet you could get 450 ohms with a 180 ohm plus a 270 ohm in series. And two 100's in parallel will give you exactly 50 ohms.   So there's one problem solved already!

> Just a couple weeks ago had to replace a 600 ohm wirewound 10 watt resistor,

 The big green one in the photo of power resistors is a 600 Ohm 20 Watt, I have a feeling I have 2 of them.  If they'd be any use to you you're welcome to them.  But I'd have to measure them first to see how close they are to 600 ohms - they are 5% and 5% of 600 ohms is 30 ohms....

@Elizabeth... "...Zero Ohm resistors are also used to enable one of several configurations of a board at assembly time. "

Dip switches are nicer, but if it's a one-time setting then Zero ohm resistors would be a cheaper way to go.  And less prone to later problems from "fiddlers"!

Apart from the usual pull-up and pull down resistors, in many circuits resistors are used for voltage drop and hence they dissipate power in terms of heat which gets waste and heats up the circuits too.

Is there an alternate way to replace such power dissipating resitors by some another circuit?

There are also resistors that should not be used in some cases:

If you design automotives ECUs (or any embedded electronic) for some German car manufacturer, they will ask you not to use higher than 100kOhms resistors, for reliability/imunity reasons. I don't know if it's the same for US car manufacturers.

If you design embedded system with large PCBs (let's say more than 18cm diagonal) subject to vibrations or large temperature swings, don't use those tiny SMD resistors packs (like 4x100Ohm in SMD0804 we use on high speed data busses). They will break open and that's a painful bug to find out ! (personal experience inside).

@Prabakhar If you have a resistor with a voltage across it and a current through it, it's going to dissipate power.  The same applies to a transistor, for that matter.

I guess there are some ways round it - I have seen battery charging circuits which used capacitors to drop the AC voltage and then rectify it to charge the battery.

For Power Supplies you have switch-mode circuits and for Audio Amplifiers you have Class D working, which improve the efficiency - dramatically in some cases,  Even in the old tube and early transistor days you had transformer coupling to avoid using large and power-wasteful resistors.   

And you can use ultra-low-temperature superconducting to reduce the resistance, as used in MRI machines and suchlike.  

And also - as seen in PC chips - use lower and lower voltages so the amount of voltage your components have to drop becomes smaller and smaller.

But I don't think we'll ever get rid of resistors completely....

OK this is very pedantic but the proper prefix for kilo is k and not K as used throughout your article.  I see this so often and it always niggles at me.  I have no idea why!  :<)

On another (possibly more helpful) note the voltage coefficient of resistance and excess noise can be significant to some designs.  On some, admittedly very sensitive, applications these can become important and it is worth noting that standard "thick" film SM resistors are poor in both of these parameters.  If this could be a problem then "thin" film SM resistors are much better in both respects.

 I thought several times when writing this that you ought to be doing it !

You did a much better job than I could've done.

Don't forget to derate power resistors for temperature. It probably doesn't effect hobbiest too much, but if you're designing a product, you need to know how much above ambient it will get in the box and the maximum ambient the product spec allows. Then find the derating curve for the resistor family you're using to find what is the real max power allowed.

@ Wnderer Don't forget to derate power resistors for temperature...need to know how much above ambient it will get in the box

A resistor run at, or near, its power rating may do so quite safely, but if it is attached to a printed circuit board (PCB) it may become hot enough to burn out the board or melt the solder and cause dry joints.

Had exactly that many years ago when I had to crawl into my attic to fix my combined electric furnace/air conditioner unit.  Household attics get very hot in places such as here in Texas USA.  Several power resistors had burned the board and melted their solder joints.  Was able to repair the damage without having to purchase a new board, but this time used reistors of twice the physical size to help keep their temperature down.

Mr. Ease wrote: OK this is very pedantic but the proper prefix for kilo is k and not K as used throughout your article.  I see this so often and it always niggles at me.  I have no idea why!  :<)

You're right.  It is very pedantic.  It may be bothering you because if you're over 50 and learned the Metric System in the USA, you were probably taught that all prefixes for positive powers of 10 are UPPER CASE and all prefixes for negative powers of 10 are lower case.   And at some point you had to re-learn it and do it the French way.  So thinking about it brings back the pain and humilation of being a STEM nerd in USA high schools during the Space Age.

IMO the USA capitalization makes a whole lot more sense than the standard, official, pedantic, French way (I'm surely repeating myself :-)  The USA convention lets you use "d" for deci and "D" for Deca instead of the infernal "da".

For a good example of the USA standard, I suggest Don Knuth's Potrzebie System of Weights and Measures (MAD #33).

en.wikipedia.org/wiki/Potrzebie#mediaviewer/File:Potrzeb.jpg

@GSKrasle: A more interesting post than one would expect!

@GSKrasle: One correction, though: The prefix for 'thousand' (kilo) is lower-case 'k', not 'K' which is reserved for temperature .

Technically you are 100% correct. Practically, more and more writers are opting to use upper-case K for electronics, because it looks better to say 1KB and 1MB than 1kB and 1MB.

On a personal front, if we do use the uppercase 'K', then this means that any units/multiples smaller than 1 are lowercase (like 1mV) and any that are bigger than 1 are uppercase (like 1MV).

@GSKrasle: Oh, and how the heck do I make line-breaks on this site? I have whole sequences of CR LF in the above ....

If I told you that, you'd know everything I know...

... and then where would we be? LOL

@Elizabeth: ...zero Ohm resistors are also used to enable one of several configurations of a board at assembly time.

But surely that's just another replacement for a jumper -- I mean that if you didn't think of using a 0 ohm resistor, you'd just use a jumper to achieve the same effect.

@Elizabeth: I've also been known to put zero ohm resistors in places where I might want a series resistor...

Good point -- I guess I would have used a jumper for this also -- but I can see tha tusing a 0 ohm resistor would alert others to the fact that thsi is where a resistor might be used -- also it lets you have an "Rn" annotation on the solkscreen.

@David: They are common IMPEDANCES, but  NOT preferred values .

Ah Ha! All becomes clear -- thanks David

@zeegllen: As for k, K, m and M, avoid M or m for large value resistors if using LTspice simulation.  It interprets both m and M as "milli" ...

I'd forgotten all about that ... give me strength! LOL

@betajet: I've occasionally seen data sheets where they screwed up and forgot to change W to the Symbol font...

I've seen that before -- I realized it was a mistake -- but I never made the connection as to why it was always a 'W'

@David: But I don't think we'll ever get rid of resistors completely ....

I certainly hope not -- the colored bands on the through-hole parts always cheer me up when I see them (that may sound silly, but it's true).

@betajet: You're right.  It is very pedantic.

You can't blame Mr. Ease -- there are some things like this that really niggle me also -- but I agree with you that "...the USA capitalization makes a whole lot more sense than the standard, official, pedantic, French way... "

If we can use Ω for Ohm, we should use Σ or some other greek letter for Siemens. Capital S is also used for Samples and looks too much like lower case s for seconds.  When I see S in a datasheet it always confuses me.

Sorry if you took offence, I did use a smiley!

Yes I'm over 50 but your other suggestions are way off as I'm English!  The SI way works well for me though and I'm happy to stick with what is the international convention rather than any national variations, which on occasions, can cause confusion.  Let's face it, confusion of imperial and SI measurements has led to the loss of spacecraft....

Can you explain the need for a US Gallon?  It's always fuddled me why it's different to an Imperial Gallon.

@Mr Ease - Can you explain the need for a US Gallon?  It's always fuddled me why it's different to an Imperial Gallon.

There are really champions of the imperial gallon? The US gallon was defined as the Queen Anne Gallon in 1821. It has a nice base 2 relationship with the other units.  If you keep dividing in half, starting from gallon, you get:

gallon, half gallon, quart, pint, cup, half cup, quarter cup, ounce.

In 1824 the British felt their system needed to more scientific like the metric system but they didn't feel like going the whole way, so they defined the imperial gallon as 10lbs of water at 62F and changed the pint from 16 ounces to 20 ounces. So it goes base 2 from gallon to half pint and the decimal from half pint to ounce. So it's a little bit decimal just like the metric system!

I didn't see you mention a couple of parameters of zero ohm resistors:  tolerance and power rating.  I've worked those into interview questions over the years to sort whether someone has practical experience with analog circuits and design practices, or not.

Using zero Ohm resisters instead of jumpers in this situation also means that the pad/hole spacing is correct to put a resistor in.

Our manufacturing plant also prefers zero Ohm resistors because they can be placed automatically the same way a regular resistor can.

Also, little know fact that zero Ohm resistor has a tolerance and power rating. We've had some of the smaller ones burn up when doing stress testing...

@Mr. Ease: Sorry if you took offence, I did use a smiley!

I didn't take offence -- I saw your smiley -- and don't worry about Betajet, he comes over as being all grumbly, but he's a big softie when you get to know him LOL

Mr. Ease wrote: Sorry if you took offence, I did use a smiley! The Betajet didn't take any offence either.  I should have included my own smiley (or smilies), but it was early in the morning.  I just saw the topic as an opportunity for some harmless fun, as Rumpole would say.

Max wrote : ...and don't worry about Betajet, he comes over as being all grumbly, but he's a big softie when you get to know him LOL

Grumbly?   I think you're judging me unfairly because of the stern countenance of my Boolean avatar :-)

@betajet: I think you're judging me unfairly because of the stern countenance of my Boolean avatar :-)

Not at all -- I've met you and your magnificent beard in the flesh as it were, and I know you to be a jolly nice fellow -- I meant that for those who don't know you, they might mistake you (via your comments) as being a big grumbly -- but, as you say, this perception may be caused by your choice of avatar -- makbe you should switch to a Charlie Brown character and we'll see if that affects your perceived persona LOL

@betajet: The Betajet didn't take any offence either...

When did betajet start referring to himself in th ethird person? Max finds this development to be somewhat disconcerting :-)

Those 10KW resistors must be gigantic!

I have one in my garage.  It holds 40 gallons of water and provides me with a hot shower every morning...

Max asked: When did betajet start referring to himself in the third person? Max finds this development to be somewhat disconcerting :-)

LOL!  I used third person in this isolated instance because you and Mr. Ease had already each used the first person, so I felt it would confuse if I became the third first person.  It was also an opportunity to use "The Betajet" like old Detective Comics that referred to the caped dude as "The Batman".

@betajet: It was also an opportunity to use "The Betajet" like old Detective Comics that referred to the caped dude as "The Batman".

@MrEase...My bad, I will consider myself reprimanded.  I am careful with m and M (milli and Mega) but K doesn't have that problem, except that, as someone pointed out. it is used for degrees Kelvin.  Not easily confused in this case but I will try and mend my ways here, I am also pedantic but not as much as you I think.   As above, I think 3k3 does not look good, I prefer 3K3, but I should be more careful and write 3kΩ or 3.3kΩ when I'm doing it that way.  Thanks for the comment.

@DT_Heyden.....Good heavens, I hope I never get interviewed by you!  But were this to happen, I would answer:

Tolerance : in most cases 10% would be fine, you could go to 50 or even 100% without too many problems in most cases though.

Power : they're in a 1/4 watt case so I would not go above that, 1/4 watt is 1/4 watt no matter how much current it takes to get to that level.  And if I anticipated this much power I would also beef up my PC tracks!

Would I get the job?

PS I see ElizabethSimon also referred to these above.

PPS - you got me curious, so did some reading....the max current levels are surprisingly low, in the SMD types especially so, considering they are effectively bits of wire.  Still, in most cases they would be nowhere near their max ratings.  I guess, because of their construction, they are actual resistors, just using very low resistance elements.  I saw resistances of 50 mΩ - which would be high for a bit of wire.

@Zeeglen, @Wnderer....had a graphic demonstration of this recently.  I did an article for the Frankenstein's Fix series about resurrecting a dead drill.  The charger circuit had a main charge path and a default trickle charge path which was just a 22 Ohm resistor, about a 1W carbon type.  A few readers corresponded with me about problems with their own chargers, and there were a few queries in forums on the net about them too.  In a lot of cases that resistor had burned the board or burned out.

When the battery was fully charged, the trickle resistor disspated much lower power than it was rated for, as it only had to drop the voltage between the power rail and the (high) battery voltage.

But if the main charge circuit went wrong, and the battery voltage was low (especially if a couple of the NiCd cells were dead) then the poor resistor had to dissipate a whole lot more power, and got very hot.

Moral of story: design for worst case and/or fault conditions if you can!

Anyone who likes MAD magazine and Rumpole can't be that bad :-)

Congratulations David! A timely "refresher" on the basics. It makes one realise how much has been forgotten over the (many) years.

Can we tempt you to do one on capacitors?

I second Ian! You should also do one on inductors, capacitors, and memristors. Then you'd have enough material for a small book! Then you'd have covered all the Two-terminal non-linear circuit elements. (en.wikipedia.org/wiki/Memristor#mediaviewer/File:Two-terminal_non-linear_circuit_elements.svg)

@Chuck, Ian....thanks for those comments!  Max has already suggested Capacitors and Inductors.   Unfortunately I have this thing called work that takes up most of my time, so don't hold your breath!  Ref Memristors, I think someone else is probably better qualified to do those.......

Actually, the k vs K debate is not all that clear, in the sense that both are used and both are in fact legitimate. Myself, I tend to use upper case always, although plenty of people don't.

See triple w allacronyms dot com / kilo / abbreviated

I think an uncontroversial example of uppercase K would be kilobyte, universally abbreviated as KB. Anyone ever seen it written kB?

David, I too thoroughly enjoyed the refresher course. The zero ohm was a new one on me, I must confess. But then again, I'm the guy who tends not to use the soldering iron at work.

Thanks Bert.  Zero Ohm resistors do take you by surprise when you first see them.  Ref soldering irons....you don't know what you're missing...I love the smell of hot solder flux in the morning!!

@Bert....I was horrified when this was first raised, I do like to get things right.  But I do approve of the US convention of factors >1 being capitalised (I guess for you that should be capitalized :-)   And while technically kVA would be right, and I have seen it, KVA looks much better.  At least there is very little risk of confusion here, unlike with M and m.  I once saw a 10 microfarad capacitor labelled 10MF.  My immediate reaction was that it could store a fair bit of energy!  Fortunately that is rare, there used to be a better, though still technically incorrect, US convention of calling microfarads mmF (milli-milli-Farads). But I digress, I should be keeping all this for the artcle on Capacitors!

I could not find mention about negative reistor. Can you make more notes on negative resistor? (I do not mean NTC and PTC, but negative resistor.)

_hm.... Negative Resistance...now there is a can of worms!.  You can't buy a negative resistor (imagine what fun you could have if you could! :-)   But you can get negative resistance in some components.  For example a tunnel (or Esaki, after its inventor) diode exhibits negative resistance over a certain part of its characteristic.  Here's one:

Over the part labelled "Negative Resistance" the current DECREASES as the voltage INCREASES - which equates to negative resistance.  Very useful with tuned circuits - if you use the negative resistance to null out the resistances in the tuned circuit that usually dampen the oscillations, you've got yourself an oscillator!   I gather they are used a bit in microwave transmitters - I recall that a radar speed trap I once dealt with used this technique.

IMO the USA should stick with capitalized positive powers of ten.  The French should be grateful that we're using the Metric System at all :-)  Long term, language is set by usage and not by académies , especially in the New World.

Next: how about we quibble about the pronunciation of powers of 1024, i.e., KiB, MiB, GiB, TiB?  I think they should be pronounced kibblebyte , mibblebyte , gigglebyte , and tribblebyte :-)

@Betajet...there are a lot of cans of worms being opened in this column :-)

Guess that some have still not yet grasped that the whole memristor story is a hoax!

@A Sceptic....sounds like there is a story in there somewhere....write it for Max and he will do the rest!

David wrote: I love the smell of hot solder flux in the morning!!

Heathkit solder flux smelled wonderful.  I think they put something addictive in their flux so customers would need to buy more kits :-)

@Betajet I think they should be pronounced kibblebyte

Quick - trademark that term before the "Kibbles 'n bits ®" dog food company gets hold of it!

@David US convention of calling microfarads mmF (milli-milli-Farads).

Good one!  Was actually micro-micro-farads, also abbreviated as uuF, but became more widely known as picofarads probably for this very reason that David points out.

I can remember several Motorola data sheets where someone had very obviously got milliamps (mA) confused with microamps (also abbreviated as mA on the data sheets).  One had to read between the lines and sort out fact from errors.

Beware when reading colour bands on a resistor with a smurf blue body.  If the paint is even slightly translucent, the blue background can show through and make the colour visibly wrong. Beige bodied resistors are not a problem.

Slightly off topic, reminds me of a story from a few years back.  HR (at a despicable company where I used to work) had just hired a degreed engineer to repair boards to the component level.  He was assigned to one of my colleagues who first asked him if he could identify components.  My colleague pointed to a resistor and asked "Do you know what that is?"

"I think it is a resistor."

"How do you know that?"

"Because it has colours on it?"

The new-hire turned out to be a SYSTEMS Engineer!  Corporate HR had no clue as to the many different types of technical skills.  He was canned within a week.

@Glen... "Good one!  Was actually micro-micro-farads "  OOPS....too right...I am getting like Max's mum and remembering things that have not happened yet :-)

Still, the use of m is confusing in this case (and I am easily confused :-)

@Zeeglen...resistor colors....been there....   I am getting quite good at identifying whether a component is a resistor, inductor (they can look very similar) or capacitor when I pull them off boards.  Inductors are usually green-y in color, capacitors often pink.   One of these days I will do a photo of confusing components, or give Martin Rowe a Component Identification quiz for his Friday amusements!

In my opinion, whoever first defined the unit of measurement for Capcitor, did not realize that the unit Farad which he/she defined is too huge for the normal electonic usage. If I am right , a capacitor of 1 Farad capacity will be almost like a room size?

That is why  all these confusions in millifarads, microfarada and picofarads and aasociated typo-errors have creeped in.

If we could have positioned that  1 farad unit somewhere at the current microfarad level then all those capacitor datasheets would look much more readable!

Farads suit well for those capacitor banks siiting on the powerlines for power factor correction.

For electronic capacitors we should coin some new unit by which we should be able to eliminate the words micro and pico from the data sheets.In stead for bigger capacitors we would be calling KF ( killo farads) and MF ( mega farads) whcih is simpler.

@Prabakhar....Unfortunately the Farad fits in with all the other units, 1 Farad when charged with 1 Amp for 1 second (which is called 1 Coulomb) shows a voltage rise of 1 Volt.  And I've tried to use the right capitalisations for the units there!

You can get 1F capacitors, they are commonly used for memory backup, and they are a bit bigger than coin cell batteries.  But they are only 5.5V rated.  You get larger ones beloved by the idiots who have 1KW sound systems in cars, to reduce the effective impedance of their battery.   I am thinking about an article on Capacitors, and will include a reference to these components for your delectation and delight....

And there is a de-facto unit equal to the microfarad, used by almost every electronics person I know: the uF (pronounced UFF). It's little sister is the pF, pronounced PUFF, equal to one Pico-Farad.    When's the last time you heard someone say "Microfarad"?

Thanks. I  Like those terms UFF and PUFF.  But I would rather call them MUFF and PUFF -  Rhyming isn't it?

Also I never thought a 1F capacitor may be available in a coin battery size. Thanks for this info.

About an inch in diameter and 1/4 inch thick (25 & 6 mm).

Muff and Puff is fine, but beware, Muff may have a double meaning in some western societies...google it.......  Uff is safer.....

I had a friend, also not from a western country, who developed an acoustic muffling garment for pregnant mothers-to-be to wear.  By the time I informed him of the unfortunate alternate meaning, he had already went so far as to trademark the name, BabyMuff.

David wrote:  Uff is safer...

Except that Uff reminds me of "Uff da", a Scandinavian expression of disgust, exasperation, surprise, and sometimes relief.   I learned it from my half-Swedish mother.

en.wikipedia.org/wiki/Uff_da

Max wrote: ... but, as you say, this perception may be caused by your choice of avatar -- maybe you should switch to a Charlie Brown character and we'll see if that affects your perceived persona LOL

OK, here's the new, improved Betajet avatar.  It's still logic-oriented, but replaces the stern countenance of "Uncle George" with the exact opposite :-)

@betajet: OK, here's the new, improved Betajet avatar.  It's still logic-oriented, but replaces the stern countenance of "Uncle George" with the exact opposite :-)

I like this one -- it makes you seem happier and friendlier -- now I'm not scared of you anymore LOL

@Betajet...is there any language you don't know?   But sounds like Uff is safer than Muff.....

And hey, what's with the new Avatar?  Bring back the old one please, it goes better with your grumbly (thanks Max) older-statesman persona.... :-)

David asked: And hey, what's with the new Avatar?

Max was scared of the old one:  www.eetimes.com/messages.asp?piddl_msgthreadid=46296&piddl_msgid=321792#msg_321792

I'm going to try the PAL for a while.  We'll see how many old-timers recognize this obscure 20th Century logic icon compared to the even more obscure 19th Century logic icon with the stern countenance.

With luck we'll meet at ESC 2015 and you can tell me which suits me better :-)

@Betajet...re PAL - I recognised it.  I have tons of the slightly newer - and reprogrammable - GAL chips around, some time I want to try make a programmer for them, they're very useful for implementing obscure logic decoders and counters etc.  Like something that decodes 4 binary lines and drives a 7-segment display directly with the HEX 0-F.

And BTW do you know who the guy was in your old icon?  I would guess at one of the early US presidents?

David asked: And BTW do you know who the guy was in your old icon?  I would guess at one of the early US presidents?

Now what would a US president have to do with logic?  It's none other than George Boole.  I've been haunted by that visage since I bought and read the Dover edition of An Investigation of the Laws of Thought (1854).

en.wikipedia.org/wiki/George_Boole

@Betajet...sorry, haven't had my morning coffee yet :-)   He does LOOK very presidential.  And if modern politicians are anything to go by, we could do with some like him.....

@Betajet...you wrote (re your George Boole avatar): "Max was scared of the old one: "

Surely Not!  He of "Bebop to the Boolean Boogie"??  But there it is in black and white.....

David wrote: Surely Not!  He of "Bebop to the Boolean Boogie"??  But there it is in black and white...

I should clarify that.  Max didn't say he was scared of Uncle George.  He said he was scared of me :-)

@max: I guess I would have used a jumper for this also....

There is a VERY good reason: if you look at a modern SM manufacturing facility, you can't place jumpers, but can place zero-ohm SM resistors.  Jumpers have to be hand-installed post-solder, and the zero-ohm SMs cost a small fraction of US$0.01 each, and the cost of placement is negligible.  For "crossovers" they are also a hell of a lot cheaper than adding another PCB layer!

n some of the motor control circuit boards, A thick PCB tracki is used as a current sensing resistor , the voltage drop across wihich gives the measure of the current.

Is this practice still followed or some alternate methods ( like Hall effect sensors ?) are more prevalant now?

@max and @betajet: It was also an opportunity to use "The Betajet" like old Detective Comics that referred to the caped dude as "The Batman". Holy Socks!, Batman

Actually,  to me  "the betajet" could be an electric rocket engine (these really exist).  It would be the type that ejects electrons (AKA beta particles) as the propellant.

Those sub-ohm SMs are usually what are called "bulk metal film" and those are generally more rugged (and temperature-tolerant) than the garden-variety SM types.

A few other comments that I don't think others covered (or not completely): power wire-wound resisitors do NOT use the EIA value tables at all for standard values; they generally are either for common needs (like the 4, 8, and 16 ohm ones for speaker dummy loads) ot follow the ancient 1, 2, 5 sequence (E3 set, although I am sure that terminolagy was invented long after it was out of common use for non-power resisitors).  Speaking of power resistors, the ceramic (tubular or square-case designs) have much higher operating temperature ranges (typically 0- 300C) and so they WILL melt solder unless special hi-temp formulations are used, unless they are heavily derated.  That's one reason the "Cantenna" had to be filled with a good grade of mineral oil (or better yet a synthetic type of coolant designed for this purpose).  It added a lot of thermal mass that gave the system a higher heat capacity so it would take much longer to reach its maximum limit.

If you REALLY want to test whether somebody is a certified old-timer, ask if they remember the old "military-style" capacitors that were color-coded with 6 dots placed in small circles molded into the case!  I "recycled" a LOT of old radios (and even some early TVs) to build my "parts inventory" up, and these generally had both those capacitors (mostly mica dielectric) along with "dogbone" resistors: basically a carbon rod with lead wires wrapped around the two ends (a double turn, then soldered with a low-tin solder so the wires wouldn't be detached when the lead wires were soldered to the terminal strips).  Of course, this long predated PCBs; it was all point-to-point wiring construction!

@betajet: your avatarian transformation has uncovered a dirty little secret about the EET blogs: your OLD avatar has been completely effaced from the annals and archives! ALL of your previous postings (and they are many, educational and enjoyable to boot) now are preceded by the DIPpy "Mr. Smiley Domino" rather than the visage they were created with.  All those who might attempt a similar bit of "elective surgery," be warned of the consequences!

"The first series was the E3. I don't know where the E came from..."

I think "E" comes from exponent , Because they are spaced exponentially across a change in value of a power of ten.

Been meaning to share this tale with you about resisters that we published on the site a few years ago - still cracks me up!  

http://www.eetimes.com/author.asp?section_id=28&doc_id=1284477

@Karen thanks - I remember reading that one when it came out, and it's as funny on the second reading.  Goes to show that a little knowledge is a bad thing......

@MHRackin - "If you REALLY want to test whether somebody is a certified old-timer, ask if they remember the old "military-style" capacitors that were color-coded with 6 dots... " 

Guilty as charged!!   I think I have some somewhere as well!  Just 2 days ago I was fossicking around in one of my junk boxes and came across a body-tip-spot resistor!  You'd remember those too??  I was devastated - I should have mentioned them in this column, with a photo.  The Body-tip-spot are coded Red-Black-Yellow, ie 200K, but it measures 221K!  Obviously a 20% tolerance one....  and it does look a bit like a dog's bone :-)  Thanks for the memories....

@Betajet....  "I should clarify that.  Max didn't say he was scared of Uncle George.  He said he was scared of me :-) "

Aah, OK.  Well in that case I would have kept the status quo and NOT changed the avatar.  Max was right - you are a big softie on the inside :-)

Maybe it's short for Equal Temperament and whoever came up with E3 liked music theory and acoustics :-)

en.wikipedia.org/wiki/Equal_temperament

mhrackin wrote: ALL of your previous postings now are preceded by the DIPpy "Mr. Smiley Domino" rather than the visage they were created with.

This is true, but I'm not usually thinking about my avatar when I write a comment.  Indeed, the "Post a comment" screen doesn't even show it.  So it's really the reader of the comment who might make the connection between avatar and comment.

I'm amused by the notion of someone with way too much time on his or her hands re-reading some of my old comments with Smiling PAL in place of stern Uncle George.  That person might say: "Wait a minute!  I thought Betajet was being serious.  Now I see that he was just being gamesome .  Now I have rethink everything."

But then, it's often a good idea to rethink everything.  That's how a lot of great engineering happens :-)

@Betajet... "Maybe it's short for Equal Temperament"

Hmmmm...interesting thought.  So if you came up with a resistance-controlled oscillator, you could use the preferred values to make a musical instrument with precise pitch?

But even as I think about this, the E series values are in decades and musical scales go in octaves a factor of 2 different from each other I think?  So scratch that theory....

@Karen... "this tale....about resisters"

It's resistOrs!  Which in turn reminds me of a cartoon I saw of a hillbilly looking type with the caption

"6 munce ago I couldn't even spel Injeneer, and now I are one!"

@ David and now I are one!

I have similar posted on my outer cubicle wall that ends in "...now I iz wun."  A joke to be sure, all my colleagues are literate unlike the stereotype.

One of my other on-the-cube-wall postings says

"I'm not a slow engineer.

I'm not a fast engineer.

I'm a half-fast engineer."

> On a personal front, if we do use the uppercase 'K', then this means that any units/multiples smaller than 1 are lowercase (like 1mV) and any that are bigger than 1 are uppercase (like 1MV).

Yeah, I always liked doing it that way too.  It's so intuitive!

> In addition to being used to jump tracks on a single layer board, zero Ohm resistors are also used to enable one of several configurations of a board at assembly time.

Some amateur radio transceivers use them to enable/disable certain frequency bands or other factory-set options.  People who needed to widen the tunable range of their ham-band radio for use on MARS/CAP frequencies, would remove one or more jumpers, or more recently, tiny 0 ohm SMT resistors.  These are things meant to be done either once and never again, or not at all, and not tampered with, so the 0 ohm resistor wins out over a switch.

> I've also been known to put zero ohm resistors in places where I might want a series resistor...

The other case I had in mind was where a designer didn't know for sure what value series resistor they would need, so they specified a resistor of unknown value, and ultimately found 0 ohms was best (or good enough).

> and changed the pint from 16 ounces to 20 ounces. 

So a pint's NOT a pound the world around?  Nooo!  Say it ain't so!

@Andy So a pint's NOT a pound the world around?

Seems a British pint gives one more beer for their money

@AndyI for some reason Liquid measurement is one of the most confusing in terms of the number of systems in use and the relations of the units to each other.  Have a look at the volume section of this Wikipedia article - there are pages of tables with factors...... 

http://en.wikipedia.org/wiki/Comparison_of_the_imperial_and_US_customary_measurement_systems

Weight is almost as bad in the small measures (grains, pennyweights, scruples and the like) but at least the upper ones (drams, ounces and pounds) are the same - in fact there are 16 drams in an ounce and 16 ounces in a pound.  Made for hexadecimal!  But above that it goes wrong again - 14 pounds to a stone and so on....

That reminds me of a post I wrote some years back that I called "A Modest Proposal' (a bow to the satire master Jonathan Swift).  I suggested that in this brave new digital world, perhaps it was time to take the next logical step after all the painful transitions to metric.  That woud be to a pure binary-base system since all calculations these days are performed on electronic digital devices.  I used the traditional English measures of weight and volume as examples of how simple such a transition would be (at least for those of us who still use or at least remember them)!

A related thought: when I was in grad school MANY years ago, studying information and coding theory, I thought about analyzing number systems regarding their efficiency from a coding theory point of view.  My analysis was based on number of different symbols required (as a measure of encoding/detection efficiency)  and the amount of information transmitted per symbol.  Much to my surprise, the resultant absolute winner as a number base was e!  Since 3 is much closer to e than 2, ternary coding is more efficient than binary!  So perhaps the occasional "contamination" of the binaryness of English-system units by a base-3 step (e.g. 3 teaspoons = 1 tablepoon) is an attempt to imrove the overall "coding efficiency" of the volumetric system! 

I sometimes use zero Ohm resistors as a "service disconnect" by putting one between, say, the output of a power source and its load. When diagnosing a failed board being able to separate parts of the circuit by removing a resistor sometimes comes in handy. They are also useful to create optional circuit paths, such as selecting one signal or another to connect to an I/O.

"Resistors are measured in ohms..." Am I the only one that thinks this is a little basic for a mag directed at Electronic Engineers? An article on dissipation of SMT parts and required copper area would be eye-opening to some, as would RF considerations and resonance issues and rise-time fun with wirewounds. Note to Chemical Eniginers everywhere- water is liquid. LOL, Greg

And you wouldn't want to drop a 1 henry inductor on your foot either! 

Supercaps are commonly available as big as 300F in a pill bottle size.

The other confusion with capacitors is the microfarad has been historically abbreviated to MFD , which gets confusing when working with SPICE type simulators , as does using 1MΩ and 1mΩ for resistors:

so  1u  =1microhenry(=1μH)  or 1microohm or 1microfarad (1MFD=1μF)

and 1m = 1millihenry or 1 milliohm  or 1millifarad (= 1000μF)

and 1K = 1thousand henrys, ohms,or farads

and 1Meg = 1million henrys, ohms, farads

One might think you would never use a 1megF capacitor in a simulator, but lead acid battery equivalents are of this size.

re  So a pint's NOT a pound the world around

It's still a pint here in Oz (rarely used), although if your'e real thirsty, go the whole "jug" = 1040ml. 

We normally use half pints over here = "a pot" or "a ten" , rarely "a half" , as a full pint would get warm by the time you finished it. 

You can drink straight from the bottle , a convenient size is the "stubby" (2/3pint?), which is standardised to fit into an insulated "stubby cooler", which fits the average blokes hand. If your'e really thirsty, go the "Darwin Stubby" , approximately 2litres = approx 4 pints.  

@Salbayeng...you didn't mention the schooner, which I thought was a universal Australian beer measure, but turns out it means different things in different Aussie states and still more different things in different countries:

http://en.wikipedia.org/wiki/Schooner_(glass)

If mankind can't standardise a glass of beer, I don't think there's much hope for it..... :-)

@Salbayeng I have seen some fairly large capacitors in electricity substations, they are used for frequency injection (putting higher freqs on the lines to switch water heaters, streetlights etc on and off) and also power factor correction.  But not room size.  And not that high capacity, either, just high voltage.  The transformers are huge, though.

@Greg....You're probably right, it is difficult to know where to start, or end.  As I remarked in the article, it could have been several times as long and not covered everything.  That sentence was followed by how to get Ω in Word, which I am sure some readers would have found useful, and some have commented on.    Yes, I could have covered the lower dissipation of SMT parts due to their minute size, but that was commented on as well.  You can always rely on the comments to fill in the gaps, usually from people well qualified to do so.  But point taken.

@Greg: "Resistors are measured in ohms..." Am I the only one that thinks this is a little basic for a mag directed at Electronic Engineers?

Personally, I rarely mind the author setting things up and creating a background to an article. Another thing to consider is that -- with the Internet -- younger folks might be doing a Google search looking for information and may land on an EE Times article, so once again it never hurts to make sure everyone is tap-dancing to the same drum beat.

Last but not least, we get managers visiting the site -- bless their little cotton socks -- and it never pays to overestimate their knowledge, because if we do so we shall surely be disappointed LOL

@Max: well put, my friend!  After 40+ years at several companies, interviewing potential EEs,  many of the EE Times readers and writers would be shocked (pun fully intended) to find the level of ignorance of basic fundamentals that I saw.  This included not only fresh graduates, but in some cases "experienced" candidates that seem to have had the same one year of experience many times over, and still didn't benefit from it!  A lot had very impressive resumes, but exposed the truth as soon as you asked them to explain exactly what they did and how did they approach their tasks.

@Greg Richter Note to Chemical Eniginers everywhere- water is liquid.

Except when solid or gas depending on temperature and atmospheric humidity.

EETimes covers a wide variety of complexity, and I fully agree with Max, Mhrackin, and David that it is wise to include basic facts for background, even for engineers.

See my comment "Colour Code" on page 5 of these comments 9/28/2014 12:07:30 PM about the engineer who was not sure what a resistor looked like.  This really is a true tale.

I'm an occasional reader, so please pardon my rudeness if I got the intended audience wrong. I look here and on EDN for things of interest to the Craft, and was a little stunned that a practicing engineer would not know all of these things, and know them stone cold. I saw the comment on maximum element voltage and was equally surprised. Really? OMFG were in trouble if so.... I agree with you, if the article is targeted to the world at large, you are abolsutely right, got to mention what a resistor is for, and Ohm's law and all that.

Lol! The solid stuff we call Ice, the gaseous version we call Steam. Water is the word we use for the liquid form, but my English my be imperfect since we do speak a non-standard dialect at Georgia Tech.... Ah, this is a bit of fun!

David & Max & other people of influence at EE Times

You can always rely on the comments to fill in the gaps, usually from people well qualified to do so.   

It's just so damn hard to find the comment you are looking for in 13 pages of comments.

1. Wouldn't it be nice (once the abitily to insert links is restored) to be able to link to one precise post? Actually the simplest would be to number each post.

2. Also it would be nice to select a particular page, rather than click through 8 to get to the one you want!

3. In the 13 pages of posts there is quite a lot of opinion and chit chat. Would it be possible to have a separate repository where comments that add to the content of the blog are stored (simply copied across)? I know it would add additional burden on someone (probabaly the blogger) to add a suitable comment, but the benefits could be substantial.

"It's just so damn hard to find the comment you are looking for in 13 pages of comments. " Agree. The commenting system needs a major overhaul. "In the 13 pages of posts there is quite a lot of opinion and chit chat. Would it be possible to have a separate repository where comments that add to the content of the blog are stored (simply copied across)? " A (working) comment ratings or "like" system along with a "Highest Rated First" sorting system might be one relatively easily implemented way to help filter out the wheat from the chaff.

2. Also it would be nice to select a particular page, rather than click through 8 to get to the one you want!

While I am on my wish list, it is also sometimes difficult to follow a thread where the response is 20 comments newer that the original. Wouldn't it be nice to be able to click to jump back to the preceding message in the thread.

And more: as a blogger I only get notified of a new post on one of my blogs when the "Post Message" (i.e. new message) is used for a post, or some one replies to one of my posts. I scan my most current blogs relataively frequently to see what conversations are going on, but if someone replies to somemthing from seveal months back, I rarely get to see it.

@Greg: ...my English my be imperfect since we do speak a non-standard dialect at Georgia Tech ....

LOL -- I myself am bi-lingual -- I speak both English and American (although I can't do the silly American accent :-)

Man speak with forked tongue?

  I look here and on EDN for things of interest to the Craft, and was a little stunned that a practicing engineer would not know all of these things, and know them stone cold. I saw the comment on maximum element voltage and was equally surprised. Really?  

At the risk of opening a can of worms (it did happen on the forum "The Connecting Edge", now gone), have you seen some of the ideas for design in EDN and Electronic Design over the years? There is plenty of stuff there that should be known "stone cold". There was one that was purely an ADC with the explanation that the output was the number written divided by the full scale... (you get the idea).

I saw an idea in a Microchip app where a zener was regarded as a brilliant new way for a low cost power supply for a micro.

Max wrote: I speak both English and American (although I can't do the silly American accent :-)

Hey Max, which American accent is the silly one? :-)

For a hilarious example of an Englishman trying to do an American accent, watch the first five minutes of the Technicolor melodrama Hurry Sundown (1967) in which the great Michael Caine tries to do a Jawjah accent (Georgia to non-natives).  Oh, it's just awful.  He sounds like he's trying to imitate Dude Boy from Tobacco Road (1941).  When he finishes his first speech, he seals his mouth with a really sour look on his face as if he's thinking "I am going to kill my agent."

Hurry Sundown is pretty much all downhill from there IMO.  Dreary waste of good actors, with most of the movie best suited to MST3K.  The exception is Burgess Meredith who is terrific as a racist judge.

@Betajet: For a hilarious example of an Englishman trying to do an American accent, watch the first five minutes of ...

I never saw this -- apart from this, my recommection of Michael Caine is that he always had the same Cockney accent, irrespective of the role he was playing ... and genereally speaking it worked for him.

@Betajet: Hey Max, which American accent is the silly one? :-)

You're asking the wrong question ... a better one would be "Which American accent isn't the silly one?"

I never saw this -- apart from this, my recommection of Michael Caine is that he always had the same Cockney accent, irrespective of the role he was playing ... and genereally speaking it worked for him.

He certainly had the cockney accent in "Cider House Rules" which was never explained.

Max quipped: "Which American accent isn't the silly one?"

I'd start with John F. Kennedy, Tom Brokaw, and Peter Jennings.  The last one is North American :-)

I'll also point out that half of Monty Python's Flying Circus is making fun of British accents.  Favorite examples include: "Oh Mr. Belpit, your legs are so swollen ", "'arold! Come back 'arold!", John Cleese's Duke of Kent imitation as Robin Hood in Time Bandits , and best of all "No more buttered scones for me, Mater, I'm off to play... the grahnd piahno ."

antedeluvian wrote: He certainly had the cockney accent in "Cider House Rules" which was never explained.

Here's my hypothesis (SWAG): After Michael Caine did Hurry Sundown , he had a chat with his friend Sean Connery, who always uses his own voice.  For example, Sean Connery won Best Supporting Actor for The Untouchables (1987) in which he played an Irish policeman with a Scottish accent [*].  My hypothesis is that Sean Connery basically said "I told you so" and that "some actors can do voices and others shouldn't even try".

[*] Thank you, John Boorman, for pointing this out.

Wasn't he from the land of "Eh? "

Max asked: Wasn't [Peter Jennings] from the land of "Eh ?"

Absolutely.  As I said, a North American accent :-)  The USA is only part of America.

Alan Rickman in 'Die Hard' nails the 'American' accent in a beautiful, effective and caricaturish way; my favourite scene! Somebody also mentioned Michael Caine's accent. There was one role in which he was so perfectly cast (at least as well as Robert Downey Jr in 'Ironman'), that it makes the whole movie, and makes it another of my favourites. And that movie is 'The Muppet Christmas Carol.'

@Antedeluvian (and others).  You can save a comment of particular interest.  I've never tried it before, but just did.... you just click on SAVE IT at the top right of the comment.   You can then go to your profile (top right of the home page where you log in) and retrieve saved content - by month if you wish.  Not a bad system, except that there seems to be no way to delete saved content when you no longer need it, so it will rapidly become huge if you use it much.

I've found the search facility in EET is not bad, if you can remember a fairly unique word or phrase in something you want to find you have a good chance of finding it.

I'd agree that when you have pages of stuff (either content or comments) it would be nice to have a list that lets you select what page you want, just highlight and/or underline the current page:

Something like that.  Much like it is, except showing all the pages.

Some recent slide shows have had a list of all the slides underneath each page so you can get to the one you want quickly.  That is also good.

Another trick that I have found useful.   If you want to link to a certain comment rather than to a whole blog.  If you are perusing the blog then the URL in your browser will be for the blog.  If you see a comment that you want a link to, click on the poster's name.  That will take you to his profile.  One of the menu items is "Content by X".   Click on that and you get a list of his or her postings.  If it's a fairly recent comment, you will find it fairly easily.  Click on it and it will take you back to the blog, but at that comment, with the URL of the comment in the browser.  Copy that and you can then send it to someone else, link to it, save it somewhere or whatever.

@GsKrasle: And that movie is 'The Muppet Christmas Carol.'

Ah -- you can't beat the classics -- my chum Steve can sing "Lydia oh Lydia" in Kermit's voice, and you's swear Kermit was in the room with you LOL

Have you seen the most recent Muppet Movie with the Russian Kermit?

Many designers don't realize that parasitic elements in real components affect their values. When frequencies reach hundreds of megahertz, basic components such as resistors, inductors, and capacitors take on non-ideal characteristics. Such changes can become critical when you design filters or attempt to optimize power delivery networks, bypass networks, or bias circuits.

While I can recognize a resistor when I see one, seeing the colorson the colr bands is another story, especially red, green, and brown. I gave up long ago and use 1% resistors because the number is printed on the side. I'm talking axial-lead resistors, of course.

See my comment "Colour Code" on page 5 of these comments 9/28/2014 12:07:30 PM about the engineer who was not sure what a resistor looked like.  This really is a true tale.

Great article on the finer points of high frequency component use, thanks Martin.  Fortunately I don't often venture into such territory, but there is certainly a lot to consider for those who do.

David: re  I don't often venture into such territory

Yes, you do, if you do high-speed digital design! Even at a clock speed of 100MHz, you need to consdier the same things as if you were designing for 350 MHz RF!  If you're dealing with things like DDRx RAM, the multiplier is even higher.  The effects of things like cross-talk, reflections, termination impedances, etc. show up in sometimes strange and mysterious ways (to those who don't think digital design has a big analog component at higher speeds).  "Noise" is what causes jitter, for example. 

At high enough voltage, every component becomes a fuse :-)

@Betajet... "At high enough voltage, every component becomes a fuse :-) "

Show me one reader of these columns who has not found that out experimentally!!

@MHRackin..."Yes, you do, if you do high-speed digital design! "   Well I don't do too much of that.  Though I am wanting to use a bunch of ICM7216 counter chips I got cheap.  They are basically 10 MHz 8-digit counter chips, but I can obviously add on prescalers to use them into the 100 MHz / GHz regions, so some of this advice will be best kept in mind!

Good for you for tackling that! If you expect to use that for signals other than multi-volt digital ones, you'll also need an ANALOG preamp with the necessary bandwidth.  Although these are readily available for very little money these days (typically in small SM 3,4 or 6 lead packages), you'll definitely be dealing with RF!  Main considerations would be controlled-impedance traces, a really good ground plane, and a barrier ground surrounding the entire part of the RF design. I'll be glad to help, although I haven't done this kind of stuff for several years, and don't have access to the kind of tools I used to use (for designing the controlled impedance traces and RF analog design; that stuff is REALLY EXPENSIVE, 5 digits or more!).

@MHRackin...thanks for that....don't hold your breath though...got a lot on my plate right now....and there are some designs around that I can work off.  I soooo need to win the lotto and retire so I can do fun stuff like this all the time!!

Well, since I'll retire a couple of months before the Dayton Hamvention, I'll have time!  And I have friends with those tools....

@Betajet... "At high enough voltage, every component becomes a fuse :-)" Show me one reader of these columns who has not found that out experimentally!!

Two more and this blog will hit the coveted "most commented" spot.

Who will be brave enough to take it over the top?

Is David ready to assume the mantle from Max?

@betajet: At high enough voltage, every component becomes a fuse :-)

When I'm giving an introductory electronic class and I get to the part about conductors (like copper) and insulators (like rubber wellington boots), I point out that everything is a conductor if you have a high enough potential -- and add that if you go out in a thunderstorm flying a kite, you will discover that your wellington boots do indeed conduct electricity LOL

 thanks for all the comments, and I thought several times when writing this that you ought to be doing it!  You've filled in a few gaps I think.

I said before you did a great job, and the number of blogs now proves it!

To fill in another gap- it occurs to me that there is a resistor type that has been omitted from the discussions (I did try to look for it in the comments, but as I have said before- finding something in the comments is not always easy). That resistor is the 4 terminal resistor (Kelvin sensing). Of course, it is possible on a PCB to use a two terminal resistor and use the tracks to create the Kelvin connection, but there are quite a few 4 terminal devices out there. I was reminded of it when I saw the 5 pins on your 3rd photo.

Aubrey: You're absolutely correct on that! This actually ties in to some of Max's stuff related to meters, in that high-current ammeters effectively have the shunt working in 4-terminal mode, and even those with external/remote shunts do too.  That is a subject all by itself, especially relating to proper PCB layouts when using high-power/high current resistors for current sensing.  You in most cases HAVE TO use a differential sense amplifier/buffer because "ground isn't really ground."  I have designed or managed designs for items like telecom -48VDC in/multiple voltages out PSUs (rack plug-in generally in redundant configurations for hot-swap without disturbing system operation) in the multi-hundred watt total output range.  Those needed current sensing on each output AND on the (redundant) inputs, and each side had its own isolated reference point.

Thanks guys.   Trouble is, it's a precedent and everyone is going to expect this every time now :-)

@Antedeluvian, MHRackin, As I said I could have filled another article.....I have a couple of lovely 4-terminal SMD resistors which you just reminded me about.  The other day I found one of the old Body-Tip-Spot color code resistors as well.  Both of them would have been great photos / mentions here.  Ah well - next time.

Ah well - next time

Save it for your book

@Chuck, Ian....thanks for those comments!  Max has already suggested Capacitors and Inductors.   Unfortunately I have this thing called work that takes up most of my time, so don't hold your breath!  Ref Memristors, I think someone else is probably better qualified to do those.......

Here's a good start for capacitors. Maxim's version is here.

There is more here and here.

Looking forward to your blog, despite your protestations.

David/Aubrey: by a strange coincidence (and we all know THAT never really happens), I just received an e-mail from sister pub EDN announcing their "new" compendium of all things capacitive! Just FYI.... maybe you can cross-link!

 I just received an e-mail from sister pub EDN announcing their "new" compendium of all things capacitive ! 

Thanks I just got it myself. Here is the link. David, half your research is done!

It is still used today. Depends on the target market and the price point for a specific product/design. There is no cheaper current measurement circuit than a well specified PCB track (in a 4-wire configuration). If you also implement a automatic calibration process during production/testing you can also achieve a very good precision. Even the frequency range is higher than with hall-sensors!

Hall sensors and closed-loop current transformers also have there advantage, especially with higher currents (where you would need very small resistors or you get problems with the head dissipation). But they are expensive.

The big advantage with this sensors ist, that they are galvanically isolated from the conductor.

If you need to use this character in your word processor, type in an upper case W, highlight it, and change the font to Symbol.

There is no need anymore to use such things as Symbol or Math fonts. Since at least MS Office 2003 (and other products from the same time) you have installed Unicode fonts providing all greek letters (and many more) by them self. This works much better when you exchange your documents with other companies/operating systems/web pages/creating pdf's etc.

I will not start the case with Excel used as a "scientific tool", I should pass your address to my EE professor from the first semester. He would beat you this ideas out of you (how he did with us) :-)

@ChristophZ.... "Since at least MS Office 2003 (and other products from the same time) you have installed Unicode fonts providing all greek letters (and many more) by them self."

Thanks for that - I had heard a bit about Unicode...but how do you get these characters into your document?

As you can see the pull down menu remembers the last used symbols. So in my case the first two entries are the Ω and µ. This way is not extremly fast but not slower than the old font change method.

At home I'm much faster, using Linux and KDE on a european keyboard (with 105 instead of US 104 keys, right alt is changed to "Alt Gr"). KDE maps a lot of symbols and scientific stuff additional to the character keys (in combination with the Alt Gr key). So at home I have a direct shortcut for the Ω and µ. I was looking for a solution like that under windows but I think I have not searched long enough.

@ChristophZ....Thanks for that, I see it mentions unicode when you do this.  And you don't have to remember all the Symbol font mappings.....

Another way in Windows 7 is to add the Greek keyboard as a second keyboard.

Start>>Control Panel>>Clock, Language Region>> Change keyboards or other input methods

In the General Tab, Select Add, Select Greek Polytonic, Select Okay.

In the Advanced Key Tab, Select Change Key Sequence

Under Switch Input Language, select the Left Alt + Shift Radio button.

Now Left Alt + Shift will switch between English and Greek keyboards. There is also a button on the task bar.

Someday I would like to figure out how to make a custom keyboard that includes stuff like temperature degrees, not equals, +/-, etc.

This blog has expanded to cover OS choices and preferences, editing shortcuts, keyboard options, etc. Amazingly (for the EET site) not one post having to do with food or eating! Max hasn't even made a passing reference to bacon! Maybe you could use bacon grease to improve heat transfer! That would be releveant for surface-mount power resistors....

@mhrackin Amazingly (for the EET site) not one post having to do with food or eating!

This recipe can be adapted to use bagels instead of pizza dough to make cheesy-bacon-brussel-sprout-pizza-bagels!

Was that link on this blog? With a record (excluding caption contest ones) 18 pages, it's hard to keep track! Or are you re-posting on this topic to ensure the "food link" string stays alive?

David, you stated "Early telephones used carbon microphones" (a bit paraphrased from your original). I know for certain (as had been associated with the manufacturer) that these were STILL in production into at least the late 1990s. Our factory (in Corinth, MS) had a special room that was the workshop of the guy whose job it was to take the special grade of coal (from a mine in Pennsylvania owned by the company) and crush, grind, and sort by grain size the carbon for these mike elements. I suspect he retired (or died???) around 2000 or so, and once the inventory of "his" carbon ewas gone, they dropped the carbon elements and telephone designs using them from their catalog. I still have a few 2500 sets (the touch-tone equivalent of the rotary-dial 500 sets that were the "modern" design introduced in late 1950s). One of them in my basement shop is still in use (although I do have to whack the handset against the top of the workbench once in a while to unpack the carbon granules).

@mhrackin Or are you re-posting on this topic to ensure the "food link" string stays alive?

I thought you were pointing out a food link was required for legitimate number one most commented status.

Touche! [seems like the EET IT gods have eliminated the ability to format the text which also allowed insertion of symbols like the "e" with a '). Or maybe that's a feature now blocked from my IE9.....  Yup!  I can see the insert link below now... I'm editing in FireFox. è (special shortcut for Canadians.....)

David, That's what the 'Alt+digit-digit-digit' method does. You can find tables for FOUR-digit access codes, but some symbols are also available in three digits. There doesn't seem to be a published list of those. You can also use 'Insert/Symbol' and under that you can see the defined keyboard shortcuts and define new ones. I don't use those shortcuts b/c I move from computer-to-computer too much.

Wndrer, ANSI.SYS did exactly what you want, but also opened the door to some juvenile pranks. It allowed you to define keys, CTRL+Keys, etc to functions different from usual. Wikipedia has a good article on it.

@MHRackin...interesting....I worked on Nortel PABXs (telephone switches) until fairly recently.  All the phone set types have number designations (2216, 2616, 3904, etc) and an analog phone is configured as a "500".  Always wondered why, now I know.  I built myself a "butt" phone when I was training (ca. 40 years ago) with an old phone handset, a mushroom tin and a rotary dial.  It had a carbon earliece.  I reconstructed the PCB to one which would fit on the back of the dial inside the mushroom tin, and used an oscillator switched to the earpiece as the "Ringer".  It was still at my place in Zimbabwe till recently, it must have been "appropriated..." - pity, as it had very sentimental attachments.  

@mhrackin... " Amazingly (for the EET site) not one post having to do with food or eating!"

Well I'd wondered about that, but thought it was cheating to introduce the subject myself...

@Wnderer: picky-palate.com/2014/04/07/parmesan-rosemary-brussels-sprouts-bacon-pizza/ This recipe can be adapted to use bagels instead of pizza dough to make cheesy-bacon-brussel-sprout-pizza-bagels!

Well since you have mentioned Bacon and Bagels we should get Max AND Martin Rowe chiming in any moment now :-)

There is a white-paper that I have found useful for trying to get better instrumentation accuracy from shunt resistors: h t t p : / / w w w .analog.com/library/analogdialogue/archives/46-06/shunt_resistors.html

@David: I didn't catch this until today! Funny thing: when I was about 10 or 11, I came across a handset from a defunct 500 set. At that time (like most folks) we had exactly one telephone. Since I spent 95% of my time in our basement (lab and workshop), I decided I needed an "answer only" phone. I constructed one with my very limited knowledge of telephony; as I had no idea what the "induction coil" did or why it was needed, I just put the earphone and carbon mic element in series, and thence to a standard phone plug. I mounted a jack on a metal bracket, and wired it "bridged" across the phone wiring (conveniently accessible in the basement just above my lab bench). When the phone rang, I just plugged in the handset; it worked amazingly well (in retrospect) although I always wondered why the "sidetone" was so much louder than a "real" telephone. These "coincidences" just keep coming! We HAVE to get together sometime to further compare notes!

@MHRackin....  "earphone and carbon mic element in series "  yeah that would give you some mean sidetone... Lol.  At one point in our telephone course another guy and I produced a very creditable dial tone with 2 relays.  Our instructor was impressed until we said we were going to box it up and sell it, then he walked away shaking his head sadly....

We do seem to have had more than the usual number of similar learning experiences.  Good excuse to get together and have a beer (or whatever your tipple is).  You going to ESC 2015 in July in Califormia??

As I'll be retired by then: my time will be my own to use as I see fit (with my wife's agreement, of course!). Unfortunately that is true for my travel expenses as well, so (other than our trip to Dayton) I'm not planning that far ahead....

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