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AoE III price lowered another $10

On Wed, 03 Jun 2015 09:08:46 -0700, Jim Thompson wrote:

Hey, speaking of goofy, in the shower this morning I invented the Larkin Current Pump. The new shower head seems to be working.

Just start with the worst current source, a voltage and a resistor. Add a negative resistor across the load to fix it. As the load voltage goes up, for every mA you lose from the source, the negative R makes up for it.

All it needs is one opamp and one quad resistor pack.

OK, Mr Self-Declared Master Circuit Designer: it's your turn.

Version 4 SHEET 1 956 680 WIRE 416 -160 352 -160 WIRE 448 -160 416 -160 WIRE 720 -160 688 -160 WIRE 752 -160 720 -160 WIRE 896 -160 864 -160 WIRE 928 -160 896 -160 WIRE 352 -96 352 -160 WIRE 688 -96 688 -160 WIRE 864 -96 864 -160 WIRE -240 -80 -368 -80 WIRE -64 -80 -160 -80 WIRE 320 -80 -64 -80 WIRE 512 -64 384 -64 WIRE 320 -48 288 -48 WIRE -368 16 -368 -80 WIRE 688 16 688 -16 WIRE 864 16 864 -16 WIRE 352 32 352 -32 WIRE 416 32 352 32 WIRE 448 32 416 32 WIRE 160 112 112 112 WIRE 288 112 288 -48 WIRE 288 112 240 112 WIRE 368 112 288 112 WIRE 512 112 512 -64 WIRE 512 112 448 112 WIRE 112 160 112 112 WIRE -368 208 -368 96 WIRE -64 256 -64 -80 WIRE 256 256 -64 256 WIRE 512 256 512 112 WIRE 512 256 336 256 WIRE -64 336 -64 256 WIRE -64 464 -64 416 FLAG -368 208 0 FLAG 688 16 0 FLAG 864 16 0 FLAG 720 -160 +15 FLAG 896 -160 -15 FLAG -64 464 0 FLAG 112 160 0 FLAG 416 32 +15 FLAG 416 -160 -15 SYMBOL res -144 -96 R90 WINDOW 0 -57 52 VBottom 2 WINDOW 3 -46 48 VTop 2 SYMATTR InstName R1 SYMATTR Value 10K SYMBOL res 352 240 R90 WINDOW 0 83 57 VBottom 2 WINDOW 3 88 55 VTop 2 SYMATTR InstName R2 SYMATTR Value 10K SYMBOL res 256 96 R90 WINDOW 0 75 54 VBottom 2 WINDOW 3 83 53 VTop 2 SYMATTR InstName R3 SYMATTR Value 10K SYMBOL res 464 96 R90 WINDOW 0 67 52 VBottom 2 WINDOW 3 76 54 VTop 2 SYMATTR InstName R4 SYMATTR Value 10K SYMBOL Opamps\\UniversalOpamp 352 -64 M180 WINDOW 0 29 45 Left 2 SYMATTR InstName U1 SYMBOL voltage -368 0 R0 WINDOW 0 82 51 Left 2 WINDOW 3 55 94 Left 2 WINDOW 123 0 0 Left 2 WINDOW 39 0 0 Left 2 SYMATTR InstName Vprog SYMATTR Value SINE(0 10 1) SYMBOL res -80 320 R0 WINDOW 0 79 41 Left 2 WINDOW 3 92 76 Left 2 SYMATTR InstName Rload SYMATTR Value 333 SYMBOL voltage 688 -112 R0 WINDOW 0 46 44 Left 2 WINDOW 3 50 79 Left 2 SYMATTR InstName V2 SYMATTR Value 15 SYMBOL voltage 864 -112 R0 WINDOW 0 51 35 Left 2 WINDOW 3 49 70 Left 2 SYMATTR InstName V3 SYMATTR Value -15 TEXT 676 277 Left 2 !.tran 0 2 0 10u TEXT 624 176 Left 2 ;LARKIN CURRENT PUMP TEXT 672 216 Left 2 ;JL June 3, 2015 TEXT 32 8 Left 2 ;quad r-pack

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin
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That's still digital, and the kids will mostly type code. They can turn motors on and off ("robotics") without knowing much about electricity or electronics.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

And that is the beauty of so much these days.

--

Rick
Reply to
rickman

It's interesting to wonder where the next generation of actual electronic circuit designers will come from. Having interviewed a lot of senior or recent-grad EEs for intern positions, it looks bleak.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin 

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Change of subject to move the focus?  

I don't see volunteers, I see critics who feel duty-bound to thwart 
your snide little attempts at games of demonizing and 
self-aggrandizement.   

John Fields
Reply to
John Fields

So, you're not a volunteer, you're a netcop super-hero!

Had any good ideas lately?

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin

Worse? You don't like the Larkin Current Pump?

Well then, post something better. As I'm sure Jim will do presently.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin 

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He didn't say _he_ had a clue, he said _you_ didn't, which I suspect 
is pretty much the truth since you seem to deal more with opinion 
than fact.
Reply to
John Fields

There are likely just as many now as there were then. Not everyone gets out of school with much practical experience. I was luck in that I had a part time job in a small electronics company which augmented my schooling with practice at the same time. A very powerful combination.

--

Rick
Reply to
rickman

[snip]

Slide R2 schematically up to above the OpAmp and any student will recognize you re-"invented" the Howland Current Pump ;-) ...Jim Thompson

--
| James E.Thompson                                 |    mens     | 
| Analog Innovations                               |     et      | 
| Analog/Mixed-Signal ASIC's and Discrete Systems  |    manus    | 
| San Tan Valley, AZ 85142     Skype: skypeanalog  |             | 
| Voice:(480)460-2350  Fax: Available upon request |  Brass Rat  | 
| E-mail Icon at http://www.analog-innovations.com |    1962     | 
              
I love to cook with wine.     Sometimes I even put it in the food.
Reply to
Jim Thompson

Dead astronauts are facts. The shuttle should have had bolt-on ablative heat shields, which would have needed to be replaced every flight, but management decided that was too expensive, since the shuttle was scheduled for a flight every week. So they used tiles.

We all know how that turned out. Challenger. Columbia.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin 

--
https://www.youtube.com/watch?v=OzHBr0ndKus 

John Fields
Reply to
John Fields 

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Geez, John, whatever happened to that little prick who pretended to 
abhor competition? 

John Fields
Reply to
John Fields

Whan I was a sprout, the only electronics to play with was analog. Old TV sets, ham radio, record players, surplus radar bits, that sort of thing. So we did that. Now there are more kids in engineering school, but few have a tinkering background, and are seduced by the charms of code and apps and "entrepeneurship". Signals&Systems and Electromagnetics - really hard hurtey stuff - are often now electives.

I found one kid with interest and aptitude for real electronics. I'm teaching her all I know. I will NOT allow her to program FPGAs. Everybody wants to do that.

--

John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin 

--
Nope, just calling a spade a spade. 

Do you have any idea why that rattles you so badly?
Reply to
John Fields 

--
I noticed the issue-dodge with your typical Larkinese bob-and-weave 
snippage, so count me out of your little "My dog's bigger than your 
dog" game. 

John Fields
Reply to
John Fields 

--
That's true enough, but what you're saying is that had you been in 
charge they'd be alive, which is your opinion and is unwarranted, at 
that.
Reply to
John Fields 

--
Can she select the colors by the numbers on the canvas yet?
Reply to
John Fields

Of course, ignorance in one area means superb skill in all others.

--

Rick
Reply to
rickman

Not to pick on you John, but we were doing that with RTD/universal instrument front ends back in the 1980s. You can get constant current or overcompensate with a bit more negative resistance and you can tweak out the sensor nonlinearity and zero the error at midrange or whatever (leaving an S-curve rather than a parabolic shape error curve). Which I **know** you know already.

I guess it's a form of the Howland pump, but less sensitive to resistor matching than the usual textbook implementation.

Neat observation that it can be done with a single 4-resistor pack (same value) and an op-amp!

--
Best regards,  
Spehro Pefhany 
Amazon link for AoE 3rd Edition:            http://tinyurl.com/ntrpwu8 
Microchip link for 2015 Masters in Phoenix: http://tinyurl.com/l7g2k48
Reply to
Spehro Pefhany

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