Recent Posts

1

Programming / Re: Linux Dependency Black Hole

« Last post by shapirus on Today at 05:36:23 pm »

PSA to all who want to develop software:
 * Do not use bullcrap like Python or docker

What's wrong with docker? It actually provides a way to create an abstraction layer to decouple the software in question from the host OS, thus helping to solve dependency issues, not to mention runtime context isolation.

* Avoid dynamic linking, link statically if possible, and therefore:
 * Avoid library dependencies like plague;

How does the latter follow from the former? If you link statically, you don't care about dependencies.

By using libraries, you avoid reinventing the wheel and avoid making dangerous mistakes. That's what the libraries exist for in the first place. Yes, there are potential security risks, like the xz case. Such cases are rare. By creating your own implementations of what would otherwise be provided by libraries you waste resources and create potential vulnerabilities on your own.

2

Repair / Re: Quick repair project - Marconi 2024

« Last post by Lodekka on Today at 05:34:43 pm »

Just to add that replacement lcd displays for 2945 and 2030/40/50 series instruments are available in case anyone is looking. Try asking on the Marconi groups.io page for more details

3

Beginners / Re: Photodiode output emulation

« Last post by tggzzz on Today at 05:34:31 pm »

Does anyone know if there is a simple RC circuit that could emulate the current output of a photodiode? I wonder if it is possible to achieve starting from a function generator, pass it through an RC circuit, and then using the obtained current pulse as input to a transimpedance amplifier. Any suggestions are appreciated.

In the late 70s I did just that: function generator->resistor->transimpedance amplifier. Worked just fine for my purposes, i.e. measuring the amplitude of a 1pW to 50µW optical signal.

No idea whether or not it would work for your purposes depends on .... your purposes, oddly enough.

4

Projects, Designs, and Technical Stuff / Re: Heated Ferrite == Useless Ferrite

« Last post by Buriedcode on Today at 05:32:11 pm »

Regarding re-using old ferrites and disassembling them: I've had some success with solvents. Namely paint thinner/white spirit.  The silicone/rubbery stuff is unaffected, but varnish and tape residue will dissolve in 24 hours.  As for heat, I've used a hot air gun - the larger 2kW kind, on a low setting, far enough away so it doesn't melt the bobbin - but its very difficult to get it right, plus its a proper hassle handling the hot cores, so I quickly gave up that method.

The solvent has worked for all ferrites salvaged from ATX supplies, but more modern SMPS transformers - specifically the sammler ones - took a lot longer.

I got a joblot of small EFD20 ferrites off ebay years ago, and every so often I'll "pickle" a batch to separate them.  I only have a few projects using those, but they worked as expected (had to change the airgap on a few, or completely remove the gap entirely), although I had to measure the core parameters to make sure they were in spec.

5

Beginners / Re: Resistor ????

« Last post by soldar on Today at 05:31:33 pm »

The value wouldn't start with black unless the multiplier band was silver, and 180 would be BROWN grey black black.  The grey/silver band has a sheen to it that differs from the pigment bands so is probably metallic silver rather than grey.   Perhaps this color-balanced zoomed in view of it will help.

Its a tossup between:
   Brown (1) Black (0)  Black(0) Silver (/100) Black () = One ohm, with a mystery black final band (as black isn't a tolerance color)
and:
   Brown (1) Black (0)  Black(x1) Silver (10% Tol.) Black (250ppm TC) = Ten ohms, 10% tolerance 250ppm temperature coefficient.

You are correct, of course. I had a brain fart there. I blame it on the flu I am undergoing.

6

Microcontrollers / Re: How to create custom bootloader in esp8266

« Last post by tooki on Today at 05:29:33 pm »

They said they want OTA (over the air, i.e. WiFi, Bluetooth, etc) updating. So I don’t think they’re referring to the hardcoded bootloader’s ability to load from serial.

7

General Technical Chat / Re: $20,000 dollars of software or licences on a thumbdrive ?

« Last post by strawberry on Today at 05:29:14 pm »

expected 3y lifetime and 1/5000 failure rate for consumer grade products
well invested 20000EUR

8

RF, Microwave, Ham Radio / Re: High bandwidth FM signal generation

« Last post by radiolistener on Today at 05:29:07 pm »

Check out the DARPA program Computational Leverage Against Surveillance Systems or CLASS.

https://www.darpa.mil/program/computational-leverage-against-surveillance-systems

We developed the computational chip over a decade ago for CLASS.

is there any public available detailed info about used approaches in this program?

9

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 05:27:57 pm »

As I understand it, SMD chip resistors are made in strips, with all steps done in strip form, and then as a final step the strips are snapped or sawed apart.

10

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by mrisco on Today at 05:27:34 pm »

New header bar

(Attachment Link)

The "New Header" version has been released in the repo.