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81

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

« Last post by wraper on Today at 09:01:40 am »

Soft ferrites are not permanently effected by heat (unless you go to the extremes near 1000 C). They however have a relatively low curie temperature and thus don't work as long as they are hot (e.g. > 150 C). This effect is however reversible. The air gap can be a big issue - there would have been a spacer that is not much different from the glue.

In therory there could be flybacl transformers with a permanent magnet premagnetization, that could be effected by heat. However I have not seen such a thing, except for linearity correction with CRTs. So I doubt one would find it in more normal PC supply - though they would do all kind of tricks to save a few cents.

It's certainly not as much as 1000^oC as I've seen cooked transformers with useless cores and no way they heated up that much while having bobbin remaining in one piece or FR-4 PCB not catching flames under toroidal one. But it's not 160^oC either. 

82

FPGA / Re: ATF1502 programming & 'wrong' id (fake?)

« Last post by c64 on Today at 09:01:01 am »

For all my projects based on Atmel ATF150x CPLDs I successfully use a homemade 'ByteBlasterMV' programming cable (on parallel port) in conjunction to the program  ATMISP version 6.7. 
More details here :

https://github.com/MattisLind/82S100replacement?tab=readme-ov-file

P.S.

I program .JEDs instead of SVFs

I do exactly same.

83

Beginners / Re: What function generator, that does a bit more than just a simple signal

« Last post by eTobey on Today at 08:58:37 am »

It is possible that it is compatible with PSG9080. If so, then can be used my tool: https://github.com/qrp73/PSG9080_ARB

This looks like a good instrument! Alltough its not so cheap, i consider getting it.

Have you used the programming feature? The manual is not so good to explain things here. Also i wonder if there are limitations when using some more complex function on one channel, for example using sweep or FM/AM/... : The other channel can be used what ever you want to do with it? Is it possible to use AM/FM/... on one channel, and sweep (with fm) on the other?

84

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by gf on Today at 08:54:25 am »

The frequency range of interest for the interpolation test is about 40%...49% of the sample rate (and the way it looks, 30%...49% for the Rigol).

There is no need to sweep. Covering this range with 5 or 10 steps is certainly sufficient. Better try to get a stable view at each frequency. If you get AM, but can't get a stable trigger on the AM envelope, then better capture a single shot at each frequency step.

The timebase should not be faster than about 10/sample_rate (e.g. 5ns/div for 2GSa/s) in order that at least 1 or 2 periods of the AM envelope fit into the screen widht when the signal frequency is 49% of the sample rate. At lower signal frequencies, the envelope period will be shorter.

85

Projects, Designs, and Technical Stuff / Re: more modern version of tl494?

« Last post by T3sl4co1l on Today at 08:53:59 am »

Not much I think, that is still simple enough to have sort-of-uncommitted error amps, perhaps the UC(C) relatives -- but they're not exactly much newer, and are legacy priced.  (At least cost doesn't matter for a "one off".)  UC3525 does go much faster (500kHz osc).

Can always make one yourself, it's nothing more than a couple op-amps, comparators, current mirrors, and logic.  An embedded version might even be feasible, if you feel confident enough to chance the survival of a 20kW inverter upon the reliability of software...

(I've written an embedded 1kW resonant control, myself; I'm fairly meh on its overall quality: it seems to work, it's not the smoothest (i.e. low noise, at least in part due to quantization but also probably sampling dither), but I don't exactly have any way to prove its correctness, or [begin to] fuzz its immunity to other software glitches or input errors.)

Tim

86

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

« Last post by moffy on Today at 08:52:58 am »

Example on my old website, https://www.seventransistorlabs.com/tmoranwms/Elec_Magnetics.html which, the magnetic theory part I think is still fine, if a bit out of style for me these days, and I do have better and more diverse inductor and transformer design methods today (but, also which aren't worth going into detail on such a page).

Thanks, saved the page as a reference, always nice to have something to assist with memory.

87

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

« Last post by T3sl4co1l on Today at 08:43:29 am »

This thread is useless without measurements

You don't need to use an SMPS (and definitely shouldn't) to do that testing.  A signal generator, capacitor, resistor and oscilloscope do a fine job.  A pulse tester can also be built, usually using a signal generator (or in a pinch, a 555 timer), MOSFET, diode, capacitors, shunt resistor, and power supply.  Example on my old website, https://www.seventransistorlabs.com/tmoranwms/Elec_Magnetics.html which, the magnetic theory part I think is still fine, if a bit out of style for me these days, and I do have better and more diverse inductor and transformer design methods today (but, also which aren't worth going into detail on such a page).

After fractures (which can be glued back together with superglue or epoxy, with care), probably burrs and varnish are the next most common fault.  Use a knife to scrape off the excess, and use a very flat sharpening stone or lap to grind the core faces flat.  If you find only the outer limbs are grinding, congratulations -- you have an air-gapped core, and the inductivity (A_L) will be low; this is suitable for flyback converters and inductors, and unsuitable for forward converters and CMCs.

Occasionally you'll see an E-core (or other shapes) that is definitely not air-gapped, and yet doesn't have a high A_L; I haven't seen these very often (and, I seem to have lost the one example that I had found..!), but, these shapes are occasionally made in powdered-iron and related materials, with lower permeability, so can be used ungapped just as any powder toroid.

As for leakage, or coupling coefficient, note this also depends upon the relative positioning of windings.  The core is not an ideal magnetic path (and even if it were, it wouldn't actually matter--), and there are plenty of flux paths outside of it, literally leaking around; wires hanging around anywhere in the space around the core, can pick up varying amounts of those paths.  You maximize coupling when the windings are, as much as possible, in the same place: adjacent layers, twisted pair or bifilar, alternating layers or strands in parallel, etc.

Tim

88

RF, Microwave, Ham Radio / Re: Transistor tester

« Last post by madires on Today at 08:42:40 am »

For example:
- https://github.com/carl1961/Transistor-Tester-AVR-Compiled-files-On-Windows
or
-

89

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

« Last post by moffy on Today at 08:31:17 am »

Well, I look forward to any follow up info you might provide.

90

Test Equipment / Re: Siglent SSA 3021X... Ooops

« Last post by wofritz on Today at 08:31:12 am »

Here is my repair:

https://www.eevblog.com/forum/repair/siglent-ssa3021x-hw-07-03-00-frontend-repair/msg4812686/#msg4812686