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Grin... I read a paper on thermo-acoustic coolers, when I was looking at a job for the gas industry, which uses them to chill (and maybe liquify?) the natural gas.... like I said I only read one physicy paper.

Has anyone done this at lower power? And can you use Helium on the bottom of a ln2 dewar to get ~10 K more cooling? (that would be fun... perhaps not all that useful. :^) ((dual stage coolers? :^)

George H.

Huh, So I could make a ~200C class A heater with a fet and the right resistor? (Resistor to take the heat load at higher temps.)

George H.

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Somehow I guess (or you said before) that there is a noise factor which mostly excludes them from the lab environs. GH

Or use a dpak resistor, or the thick-film equivalent, and PWM it. But use the right solder.

Grin..the last heater I made had solder as the thermal fuse. (unintentional) The leads on the to-200 resistors would melt the solder during overload. ~10% of the time the resistor would die too.

GH

Jun 19 PBSS303NX, PX and friends?

Why a chip ? You can't design a PWM circuit ?

Heat pipes are useful only if you have a cooler environment into which to dump the generated heat. Not usable for cooling below environment temperature.

Compressing ambient air into a high pressure will heat it up, so the heat can be dumped into the environment through a heat exchanger thus getting compressed air at about environment temperature. Letting the compressed air expand to environment pressure and the air temperature is below environment temperature and can be used for cooling. Of course, the compression requires external energy.

Uh, I've made dozens from scratch. That's why I know I have better things to do, than spend multiple revisions optimizing a relatively fast converter, just to end up with something sprawled over multiple square inches, and performing poorer than everything already on the market.

Tim

OK, dead old, known to all. 8 bit PICs mostly works fine at 180'C, even the ones labelled 85'C. Not for ever, but for a long time.

Bipolars leak and Vbe drops, so Si sort of becomes Ge. FETs are much better in this respect, and many nowadays are rated to 175'C anyway with no price penalty. I have an analog power stage using TIP3055 and 2955 which works fine at 180'C, the Tj must be about 210'C.

One of the trickiest things is capacitors, C0G are often ok, but X7R reduces several fold.

There's a selection of various parts which do work, op-amps, references etc, and a much bigger selection which won't. Sometimes a lifetime buy is advised if there's a chance that a manufacturer will change the process. Packaging is an issue - solder gets weaker and there's differential expansion to consider.

I enjoy the work as it suits an old bloke - you can't just bung in the latest greatest uC, and so you need to get the best from limited resources, just like in the olden days. If there's some surface electronics, you can do what you like.

Yeah, there have been pilot plants built for stranded gas--fields too small for a pipeline to be economic. IIRC they burned about a third of the gas to liquefy the rest, which is a big win compared with flaring it off.

The Los Alamos group (Greg Swift et al.) have published some TA design codes that seem to work OK. Swift's ebook on TA is a pretty good read.

Dunno. The thermoacoustic instability depends on transient heat storage in the ceramic tubes, and of course everybody's heat capacity drops at low temperatures. Might still work at ~70K.

Cheers

Phil Hobbs

TCA0372 has to be the undisputed champ. Dual 1-amp, 40 volts, 47 cents.

Strangely, no power pad.

t.

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Thanks, constraints can be the fun part.

GH

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OK thanks, GH

I really like these thickfilm resistors. They drop into a DPAK footprint. This is a Riedon. Ohmite has similar parts.

R31 will be a thermistor!

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Sounds like an excellent product for ElectroOptical Innovations LLC?

An innovator's paradox, when pitching an idea, is that if the persons being pitched were capable of imagining it, they would've already done it. But if you build it, when they see it, they'll want it.

(YMMV)

Cheers, James

It looks like a fairly thin package. (though it might be the camera angle.) I assume you like it 'cause it couples well (thermally) to the package. Which would 'make sense' thermally, the less distance the better.. (bigger C though.)

The to-220 packs are not so great thermally*. But a screw hole is great sometimes.

The thermistor is cute.

George H.

Did you run into the bouncer at the Palais de Danse? ;)

Cheers

Phil Hobbs

(Ancient Emerson, Lake, & Palmer / music hall reference)

It's a bit far afield, but not out of the question. We're a lot better at technology than marketing. ;)

If they have any idea what it is, and if it isn't too far out of the box. I've posted before about my experience 20 years ago at IBM, when I came up with a low-resolution thermal IR camera that had highly competitive resolution and performance, for about 40x lower cost compared with existing solutions.

A large control systems outfit whose name starts with 'H' and which is best known for gold-coloured round thermostats was very very interested. They were buying about 2500 of these $4k cameras per year. We showed them a solution that had a BOM price way below $100, and asked for a per-unit royalty of $50.

What we expected them to think: "Our costs will go from $10M to $250k per year--let's buy a house in Aruba!"

What they actually said: "That's a FIFTY PERCENT ROYALTY! ARE YOU OUT OF YOUR MIND?"

I didn't really understand what "inside the box thinking" meant until that moment. :(

Cheers

Phil Hobbs

Well, if you can stand cryopumps, you can probably stand TAs. ;)

Cheers

Phil Hobbs