[fun] Weird electronic circuits collection

Didn't Vyvyan throw the toilet out the window in the young ones, to avoid the toilet tax? I read that the toilet tax is being / has just been reintroduced in some form.

how do you do those 3?

Terrible capacitance tempco, but is it worth the additional circuitry you need to turn that into a temperature signal?

NT

There are also FET stages that work in both directions in transceivers. I think the Atlas 210 and 215 series are among them. I've got one that still needs repair.

Ah yes. That was the best evocation of student life in the 70s :) Given one of the houses my daughter lived in, I'm not sure it has changed too much. Three examples: - a hole appeared in the kitchen floor (not a trapdoor like in my kitchen floor) - the boiler failed, but one shower continued to have hot water; apparently it was fed from next door! - there was a problem with the electrical distribution where it entered the house. The electricity companies refused to touch the equipment because it was too old and couldn't be isolated

The superregen.

That trick of putting current boosters controlled by resistors in series with the supply pins of an op amp.

Avalanche transistors.

SCR inverters

Magnetic parametric dividers for generating 20-Hz telephone ring tones from 60 Hz

Cheers

Phil Hobbs

I sketched out an idea for a one tube regenerative reflex radio a while back but haven't had a chance to build it yet. I should do that before the end of the winter to take advantage of the good SW listening season

They have weird wiring in the UK. As a student I stayed in a cheap London hotel. You had to insert a coin into a box at the end of a long hallway for a few minutes of hot shower water, then run as fast as you can to the _other_ end where the shower was. Tick-tock-tick-tock, every second counted. The timing was a bit erratic and occasionally it blitzed off mid-stream. Ice cold water shot out. YOUWEEE! Then you had to insert another coin. However, now you were naked and soaped up, plus there were

Yup, they put a perforated metal plate in there instead of a phosphor screen; perforations just happened to correspond to binary codes. Apply deflection, you've got an ADC!

More involved tricks, I'm not sure, but that's a good example.

Parametric amplifier, I assume.

IIRC, there was an HP electrometer that did this. Varicaps have low leakage, thus, parametric op-amp with much lower input bias current than other methods.

There's a lot of "measure thing with completely different property" in physical instruments, like atomic structure by resonant frequency (AFM), or gravity waves by interferometery (or every other damned thing with interferometry, because it's so good). It seems odd to apply the same principle with electronics (as you're starting and ending with electronic signals), but sure, why not? :)

Tim

Just make an LC or schmitt oscillator where a bit of the PCB is the capacitor. It's ideal for compensating FR4 problems elsewhere on the same board. An FR4 PCB cap has a tempco around -900 PPM/K.

Silicon diodes are used as temperature sensors at liquid helium temps. Below 20K, the tempco gets extreme.

One liquid helium level sensor is a vertical piece of wire in a tube. Apply current and it gets superconductive in the liquid and resistive in gas; measure the voltage.

Core memory is actually pretty weird.

The most famous is the Philbrick P2. Pease wrote an article or two on it.

Cheers

Phil Hobbs

Shock lines, NLTLs, are cool; a transmission line with nonlinear elements. A voltage step gets faster as it propagates down the line. It has been done with varactor diodes, hi-K capacitors (discrete and continuous strips) and with saturating magnetics.

Nice trick. I was guessing you used it as temp sensor for a power pass element.

George H.

I've heard a rumor that you have to pay a tax in the UK just for having a television. But that's too silly to be real.

That was always the case in Germany as well. AFAIK they now went farther and made it a poll tax. You are by default presumed to have access to radio and TV, even if just through a computer somewhere, so you must pay radio and TV tax.

Tis (almost) true, I admit.

It has an interesting side effect: every hour contains >58 minutes of TV program. And often a high quality programme.

And, of course, you aren't the product being sold.

Very few British people would have it any other way.

We get the BBC mysteries. It's shocking how many murders you guys have.

Yep, done with a swept function generator that makes a curled trace, and minimize the transmitted light through a negative of a cloud-chamber track. When the curvature matches the trace, the output light signal dip tells you what the track curvature was...

Oscilloscope/photocell with a paper mask to make arbitrary function generator.

because one can? You do get light as well as sound. And VFDs are free. And they can run direct off the mains.

NT