Recent Posts

1

PCB/EDA/CAD / Re: JLCPCB alters soldermask without any notice

« Last post by Infraviolet on Today at 10:17:32 pm »

I had an issue once where JLC cut out a milled slot in a weird way such that it was at an angle to what my gerber specified. I was using the confirm-before-production option, but the gerber I confirmed for was correct, so this error got introduced after my review and confirmation and it wasn't known by me until the boards showed up. JLC had a quality complaint facility in their website, I sent them a photo of the PCB slot that arrived vs what it looked like in my original gerber and they gave a refund (money off next order) on those boards from among a larger order. With luck you might be able to get that from them for this soldermask ****-up.

2

Other Equipment & Products / Re: T12 STM32 V2.1S Soldering Station Controller - schematic etc.

« Last post by floobydust on Today at 10:16:54 pm »

I thought the 245 thermocouple has 2 junctions and thus too much output for the usual T12 op-amp configuration.

3

Test Equipment / Re: Agilent 4338B adjustment program

« Last post by TheDefpom on Today at 10:16:52 pm »

yeah me too, I just purchased a broken unit (not in my hands yet so it may not even need it).

4

Test Equipment / Re: New Zoyi multimeter+oscilloscopes - ZT-70xS, up to 50MHz/250MSps (nov 2022)

« Last post by Vapor8 on Today at 10:16:32 pm »

I did some tests with the Zoyi and some other meters I have access to. The AD780 was trimmed to give a 2.5000V output on the (old) HP desktop meter. The film capacitors were measured with an Agilent 4294A impedance analyser at 10KHz. The table shows that my 703S gives the results closest to the ones by the more advanced equipment. Yet most of the meters tested do well enough for most situations. Even the 10$ T7 component tester gives great results!

Would you mind sharing what version firmware the Zoyi 703S used in your testing has? Thanks!

5

Programming / Re: Angle wrapping in code, "easy" problem, need to double check

« Last post by ejeffrey on Today at 10:15:40 pm »

In languages like C and C++ where % is modulo, not truly a remainder and therefore returns negative results when negativeNum % positiveNum is done.

The C C++ way is generally called remainder, the sensible way is called modulo.

6

Test Equipment / Re: New 2ch pocket DSO+SG - Zeeweii DSO2512G

« Last post by Sham73 on Today at 10:09:42 pm »

That's OK, just don't overdo the calibration, it won't be like a multimeter.

For calibration, I need a more or less accurate laboratory power supply and a functional signal generator, which I don’t have.

If you don't want to spend much, I purchased a cheap device like this one https://www.aliexpress.com/item/1005006786894152.html it comes with a hand written paper with the real measured values with good equipment and also states the date and temperature when they were done, it can be used to know how good are the measures of your equipment.

I have such.  I purchased it to determine the accuracy of my Owon B41T+ multimeter.  It only has four values ​​from 2.5 to 10 VDC, so I didn't mention it.

7

PCB/EDA/CAD / Re: High current traces meeting small component legs

« Last post by Infraviolet on Today at 10:08:30 pm »

Thanks for the extra details. All the online calculators I've found use a model where the trace in which the current flows is the only copper, and it isn't connected to bigger pours for heat dumping, so are there any rules of thumb or empirical equations to approximate (to the nearest 10 celsius maybe) how much temperature rise you get when you have a short, narrow high current trace where the current actually flows but connected by copper to a much bigger pour (or even a pour on both sides with lots of unfilled thermal vias to increase the surface area contacting the air) some distance away.

8

Projects, Designs, and Technical Stuff / Re: PC74hct4046ap Replacement

« Last post by dj_holmes on Today at 10:08:02 pm »

Accordig to this post IR LED is even less noise!

https://www.diyaudio.com/community/threads/some-noise-measurements-for-leds-and-zener-diodes.35821/

9

Beginners / Re: Convert US standard 115V to International 230V

« Last post by soldar on Today at 10:04:07 pm »

I agree that the statement is a simplified explanation of how a SMPS works. But if you look at main stream switching power supplies on the market they are designed for a broad range of frequencies and input voltages. You need to choose a power supply rated for the application to which it is intended. There are SMPS's rated for medical applications. So why reinvent the wheel just get a power supply rated for your application.
Electrolytic's  standard testing is between 100Hz 20C^o and 120Hz at 25C^o. The DC ripple in a SMPS after rectification is either 100Hz or 120Hz.
Electrolytic capacitors show very little change to behaviour between 10Hz and 1kHz depending on temperature. So to say that there would be any significant change in behaviour between 50Hz and 60Hz at an ambient temperature of 20C^o to 25C^o is over thinking that a problem can occur. https://www.cde.com/resources/technical-papers/AEappGuide.pdf

You are missing my point. It has nothing to do with SMPS. The point is that a bridge rectifier followed by a capacitor is highly dependent on frequency because the capacitor needs to hold enough energy to power whatever it powers during a longer time, until the next pulse to recharge it comes along. Lower the input frequency and you increase the   ripple, decreasing the voltage level to which it falls. If you reduce the frequency by 50% you need to double the capacitance in order to maintain ripple and not increase voltage drop. It does not matter what follows, SMPS, linear or whatever.  I have dealt with adapting 120 V, 60 Hz machines to 220 V 50 Hz, including linear PSU, motors and transformers and I am quite familiar with the issues. That was long time ago, in a previous life.

10

Power/Renewable Energy/EV's / Re: Totem Pole PFC is over-hyped?

« Last post by coppercone2 on Today at 10:00:44 pm »

and its not a problem for them because you managed all three companies and saw software implementation for a hardware power systems control go down smoothly?

its a crux if there ever was one. Treez is wanting to bleed less money. I can understand that, actually, and it makes sense that removing a software requirement would make things go smooth.