AoE x-Chapters - 1x.2 Resistors

The Caddock and Ohmite 50r DPAK parts run around 5 pF from element to tab, and are very fast. They TDR like you would expect, with the probably-serpentine resistive element looking like a lossy transmission line. It's all over in a couple hundred picoseconds.

Caddock makes a resistor

that is almost perfect. Stick a 450 or 950 ohm one in to an SMA female on the end of a coax, and you get a cheap 3 GHz probe.

HP wanted about $3K for that kit.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Giant electrostatic voltmeters were fun.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

OTOH, it does add local color reminiscent of Bob Pease to a potentially dry tome. Although Pease would've probably said something along the lines of:

John Larkin of Highland Technology wrote a nice explanation of his pulse-power torture machine in sci.electronics.design ...

This local color also functions as an Easter egg that enables insiders to feel special, to be "in the know," regardless of how they feel about Larkin.

Thank you, 73,

--
Don Kuenz KB7RPU 
There was a young lady named Bright Whose speed was far faster than light; 
She set out one day In a relative way And returned on the previous night.

Yeah, for settings near mid-scale you get a nice vernier action, but you can have the whole range if you need it. Figuring out new nonlinear curves you can get from a loaded pot is recreational, too, like making AM radios out of 555 timers. ;)

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs 
Principal Consultant 
ElectroOptical Innovations LLC / Hobbs ElectroOptics 
Optics, Electro-optics, Photonics, Analog Electronics 
Briarcliff Manor NY 10510 

http://electrooptical.net 
http://hobbs-eo.com

One not so technical thing about resistor arrays is that a quad array is more expensive than 4 single resistors , but production cost is a lot lower for the quad so Cost Of Gods Sold is cheaper for the array

Add to that better matching and drift, but worse PCB routing (if function is spread across the board)

Cheers

Klaus

We can see it differently. I know Win a little bit from here, but with people I know nothing about that sort of stuff is just noise that gets in the way of the signal. And most readers won't know him at all.

A dry tome? If you don't want that you won't be buying AOE :) It's a book of engineer's factual info, not a junk soap.

NT

I don't remember seeing anything on metal staple resistors. Carbon comp got a lot of mention but not carbon film. Were printed-onto-pcb Rs mentioned? I don't remember. Oh, something I don't think was, and am not sure if usefu l: how may R values you can get from each size of R-pack. Oh, also use of o ther components as Rs, primarily filament lamps & neon lamps.

Also, and not sure if relevant, R stocking policies for mfrs. Eg if you red uce the number of R values your board takes, it's slightly cheaper to make. Less purchases, less time. Also if you give a range of values in your part s list, as I usually do where practical, you can often sub with what you've got. In some parts of the world that has some use.

Then there's robustness of sm versus TH. And mounting options for power Rs. And the pros & cons of fan cooling... And of course tricks to avoid the energy lost in power Rs.

Resistors are far from futile.

NT

Thanks, I think. Actually we're a little of each; we get tired of the endless spreadsheets of parts data, bench meas, writing dry-tome stuff, and Paul breaks out in the Big Lebowski, or whatever. Gotta jazz up the stories.

And we love name dropping. John sends us his huge resistor fixture, we explode it, damn right we fess up. Are we gonna post pictures, claim we made it?

OK, could ... Nah.

--
 Thanks, 
    - Win

AoE has always had a relaxed folksy feel. Transistor man, for instance, is in the first ed. I'm happy that is not going away. :^)

George H.

I have a spreadsheet for that, not for the general loaded case but for the one-side-loaded case, with a series resistor on the ground leg, so that it can be made to approximate a log pot. The approximation is best for small gain ratios, understandably.

Tim

--
Seven Transistor Labs, LLC 
Electrical Engineering Consultation and Design 
Website: https://www.seventransistorlabs.com/

Transistor man vs Ebers-Moll, mumble frotz. Ebers-Moll for me.

Cheers

Phil Hobbs

(Relaxed and folksy is key, though.)

Some more... Mains bleeder resistors run within ratings tend to fail. Typical V ratings for various R types - IIRC you touched on it but didn't give the reader much idea what to expect from what parts, something that surprises many. HV R stacks & reliability. Fusible/safety resistors. V ratings: end to end & case to external differ V ratings & pots, why so many fail in mains dimmers Life ratings of power Rs Reducing cost of power Rs by using distributed small Rs

Maybe one day you'll end up going to a series of books.

NT

On a sunny day (5 Aug 2019 14:44:40 -0700) it happened Winfield Hill wrote in :

You probably know I am not a big fan of your books amd never have read those apart from the things I found here and on the web. Now you are moving into the realm of destruction, have you ever written about construction of things we used and use everyday such as radio, TV, the old way, how to design one, how to write the software for the newer systems (DVB-S DVB_T and their newer generations), as hardware and software is really both an essential part of electronics these days. I know books have been written by others about that, very good ones, and you cannot be an expert on everything but what is part of our daily lives is an essential aspect in my usual NSHO, but also because I did all that.

You asked for feedback, here it is.

Can you still get those anywhere, or something equivalently proven? I had a look a while ago for some tricky probing, but couldn't find a source (in small quantities, anyway).

? David

Sure, Caddock sells them. I got 5 samples. They are good for probing kilovolt pulses, too.

Caddock is great to work with and makes some really interesting parts.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

Well, I am a lot better at blowing up parts than you are.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

You should get, and read, AoE3. Really.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics

I thought this might be in the book, but if you're covering resistors in depth in the X-Chapters then maybe it's worth remembering there was a pretty long thread about this and the minimalist solution wasn't obvious at first.

---------------------------------------------------------------------- Don't do this! Just don't! John Larkin 1/19/03

OK, every once in a while we need to have a trimpot crank in a little bit of DC offset into an opamp or something, and there are those nice

+-15 or whatever power rails handy. But I see so many presumably intelligent engineers do something like this: +15----------+ | | 10k | | P 100r O

If you think that's bad, I've seen many circuits in the past where adjusting a preset pot to one end of its travel would destroy a transistor. That was somewhat common at one time.

NT