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Beginners / Re: Convert US standard 115V to International 230V
« Last post by Jwillis on Today at 08:16:06 pm »

The transformer really doesn't care if it's 50 or 60 Hz, it'll run fine either way. If it's a
50Hz transformer it'll actually run slightly cooler at 60Hz because it may have more
copper in it. And a SMPS will generally also run OK at either line frequency.
Unless there's some kind of frequency sampler circuit that wants to see a particular
line frequency(which would be rather odd), it's not worth the bother to design the
device for one or the other.

On a SMPS, frequency of the mains voltage doesn't matter because the mains power is rectified to DC then the frequency is set to a by the PWM for the transformer.
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Pet peeve: Hackers.

Instead of spending an evening watching movies on Friday night with my wife, I spent over an hour on the phone with Netflix after a hacker hacked my account, changed my password and the email associated with my account, and locked me out. Bastards...
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Security / Re: Microsoft repackages apps with a telemetry .NET wrapper
« Last post by bd139 on Today at 08:14:22 pm »
Your reasoning is detached from the outcome.
That’s a rather lofty accusation.

I worked in the software industry for years, and at a usability agency. I have relevant, real-world experience with this, and am not the deluded simpleton you essentially accuse me of being.

I'm not making an accusation. I'm just stating that the data and the intent do not always end in the conclusion that people think that they do.

I would suggest that the "usability agency" is a considerable bias as well based on my other comment. Literally there is no business if you tell the client not to touch something, so the default state is that a change must be made otherwise there is no report to make.

The reason that we stopped hiring agencies to run user studies for us is that at no point did anyone run a baseline analysis against a null hypothesis i.e. no change. I got into a hefty argument with a consultant over this who said that a change is 100% necessary, without providing any evidence and before the study was run. That is a complete lack of objectivity, intellectual and professional integrity in the industry.

The end game of two large, well known agencies being hired was that we had to roll ALL the changes back because it crippled clients.

This cost us a LOT of money. Try writing off a couple of million GBP and you'll see where the ROI is.

I literally gave a real-world example: the post-pasting popup menu in Microsoft software (Office, etc). Usage telemetry had shown that the “paste” command is very frequently followed by “undo”, because the result was not as intended. Then people would either use a Paste Special command, or paste it normally and follow it by manual reformatting. So they added the little popup that lets you change the pasted formatting in situ. I think this is a fantastic feature, and well-implemented: it makes it easy to recover from an unexpected result, yet doesn’t force any change to one’s workflow at all: you can also simply ignore it and fix the problem in the old ways.

Personally I think that's a shitty feature because it doesn't work like anything else in the rest of the OS or any other software. It's literally an edge case coded into the office UI runtime.

Compare to "Paste and Match Style" on macOS which is system wide.

I don’t disagree in principle with that statement, but maybe I’m just not quite as jaded as you.

It's not really jaded, but experienced.

Put it this way, who's the last person you go to for financial advice? Actually a financial advisor. Why? Well it turns out that they have two principal objectives (a) earning commission and (b) reaching sales targets. That gets you a mediocre outcome. What gets you the best outcome is developing an understanding of the domain and the problem and that comes from a proper study and analysis, not witchcraft and hope for a fixed price.
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Beginners / Re: LC filtering for combined Vref/VDD of ADC
« Last post by HwAoRrDk on Today at 08:11:47 pm »
I just had a thought. I am buffering the inputs to the ADC with op-amps because I need to have a very high-impedance connection to what is being measured. Should I re-organise the filtered 3.3V so that it is supplying these op-amps as well as the ADCs? Otherwise, will the op-amps just be passing power supply noise into their outputs? Although, I do have RC filtering on the output of the op-amps...
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Beginners / Re: Convert US standard 115V to International 230V
« Last post by soldar on Today at 08:11:29 pm »
The transformer really doesn't care if it's 50 or 60 Hz, it'll run fine either way. If it's a
50Hz transformer it'll actually run slightly cooler at 60Hz because it may have more
copper in it. And a SMPS will generally also run OK at either line frequency.
Unless there's some kind of frequency sampler circuit that wants to see a particular
line frequency(which would be rather odd), it's not worth the bother to design the
device for one or the other.
If you bother to read the thread you will learn that this is not relevant or applicable.

And, as a general statement it is also wrong.
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Test Equipment / Re: Test Equipment Anonymous (TEA) group therapy thread
« Last post by bsdphk on Today at 08:07:27 pm »
I need help identifying a Tek scope plugin, for the most obscure reason you can possibly imagine...

First two (huge) photos:

https://datamuseum.dk/bits/30006763

https://datamuseum.dk/bits/30006749

These photos were taken in Stockholm in early 1955 by Bent Scharøe Petersen, and show the setup he used to investigate if the brand new "magnetic core memory" technology was any use for the IAS-derived computers being built in Sweden and Denmark at the time (BESK, SMIL, DASK)

There are also photos of scope-traces, with handwritten descriptions which either read "20µs/cm" or maybe "20ns/cm":

https://datamuseum.dk/bits/30006678

So which is it ?

The scope is a Tek 735, which does not seem to have a serial number.

But I have been unable to figure out if the plugin is 53A or 53B ?

My personal guess is that it "20ns/cm", mostly because "20µs/cm" would make the signals very slow compared to the IAS-derived computers.

If it is 20ns/cm, the signal is 25 MHz, and as I understand it, the 735 should be able to do that with a 53B ?

Thanks for any help.

PS: All the 200+ pictures are here:

https://datamuseum.dk/wiki/Bits:Keyword/PERSONS/BENT_SCHAR%C3%98E_PETERSEN/PHOTOS
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Test Equipment / Re: Second bench PSU, am I thinking about this correctly?
« Last post by krby on Today at 07:58:03 pm »
Ok, so what I'm inferring is that rather than looking at "better end of cheap" like the Korads, I should be looking at the cheap end of better brands like Rigol, Siglent, and others.

Also, any advice on 30V/5A x1 or stretching to get a multi-output parallel/serial-able that I could then treat as a full replacement of my 10A cheapo PSU?
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Test Equipment / Re: GSG-5 Series GNSS simulator and exploration
« Last post by ArsenioDev on Today at 07:55:02 pm »
Bad news, Looks like the unit I obtained is broken in odd ways. Ethernet is non-responsive and does not initiate a link, USB fails IVI with a timeout and I cannot update the firmware.
Did however obtain the firmware chain from Safran, I will repost it when I am back in the office for future ref.
If anyone has a 2014ish vintage of GSG Studioview it would be appreciated, would like to take one more attempt at cracking it onto a newer firmware rev before giving up.
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Beginners / Re: Bulk input caps and impedance
« Last post by Jwillis on Today at 07:52:46 pm »
A split out question from my other project.  Trying to pick out some of the basics I might be missing.

If I put a cap directly across a DC barrel jack input, then when I connect the power to it, I will get a spark and the supply will basically see a 0 Ohm short for a fraction of a second and a load which seems to want to pull an ideally infinite amount of current.

So, it seems to make sense to put at least a "token" value resistor in series before it.  That or one of them magical to me, inductors.

As it is a bulk input cap, it has to be able to pass at least the average current of the load.

True an ideal capacitor will "Draw" infinite current provided their is an infinite supply. But if restricted to 5A then the maximum is 5A. Now even 5A seems to be a lot, so Lets look at the mechanical structure of the circuits leads and internal plates of the capacitor and compare that to the fusing current. Typically you would see that 20AWG (capacitor lead gauge for a 100uF capacitor) is capable of 5A. But the fusing value of 20AWG is 158 A for 1second or 882 A for 32 mili seconds. https://en.wikipedia.org/wiki/American_wire_gauge
As you can see the amount of current that a simple piece of 20AWG can handle is incredibly high for short periods of time.


The Time Constant RC is variable as this is dependent on the series resistance and capacitance of the circuit.  https://en.wikipedia.org/wiki/RC_time_constant
But typically the charge time of 1RC (63.2% total charge or peak supplied voltage) is only a few micro seconds. By that time the amount of current across the capacitor has also dropped by  near 63.2%.
Of course you can lengthen the time constant by adding a resistor in series with the capacitor there by increasing the ESR, but keep in mind that that resistor will also slow the discharge of the capacitor. So in a PSU filter this becomes undesirable because slowing the capacitors charge and discharge will increases output ripple voltage. Also depending on the value of the resistor and the desirable RC time constant that resistor begins to heat up over repetitive charges and discharges of the capacitor. Typically you don't want the capacitor to discharge lower than 63.2% per cycle. You can work out the dissipation factor of the capacitor if you like. https://en.wikipedia.org/wiki/Dissipation_factor

So for filter capacitors, in your PSU, you want low ESR with a low dissipation factor.  A capacitors operating properties are listed in the data sheet and you would look at that to see if the capacitor your using is adequate for the application.




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Be sure to read the fine print on the pre-done certifications and special instructions from the module supplier.

For example:
"Single Modular Approval. Output power listed isconducted. Grantee is responsible for
providingspecific testing instructions to host manufacturersfor additional testing to verify
compliance as acomposite system. This includes retesting oftransmitter module per part
15.31(h) and (k) andverification of compliance with FCC RF Exposurerequirements. Separate
approval is required for allother operating configurations, including portableconfigurations with
respect to 2.1093. Theantenna(s) used for this transmitter must beinstalled to provide a
separation distance of atleast 20 cm from all persons. OEM integrators andend-users must be
provided with transmitteroperation conditions for satisfying RF exposurecompliance. The
device contains 20MHz and 40MHzbandwidth
"

Safety certifications, lead/other harmful chemical certifications may also be needed.  Some countries need you to have a cradle-to-grave plan for the materials which can include special recycling instructions to the consumer, etc.
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