Recent Posts

1

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.

2

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.

3

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/

4

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.

5

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.

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Projects, Designs, and Technical Stuff / Re: Control of 2 CAN Open DS402 motors on a single shaft

« Last post by moffy on Today at 09:52:57 pm »

For the torque/current controlled motor it will be important to keep the torque command below what is needed otherwise it will  tend to run away, speed wise, and yes the torque needs a faster loop because it needs to react to load variations. How dynamic is your load ? It also depends on how fast your control loop is compared to the dynamics of the system, lag is a killer for stability.

7

Test Equipment / Re: Heads up on MicSig Probe

« Last post by WattsThat on Today at 09:47:47 pm »

Just grabbed one with the same deal.

Thank you very much for posting!

8

Projects, Designs, and Technical Stuff / Re: what certification is required to sell electronic products?

« Last post by Retirednerd2020 on Today at 09:45:01 pm »

Does anyone have an estimate of what this costs these days?  Last time I ran a product through for safety for USA and Europe to UL60950/EN60950 (IT Equipment) using TUV as the testing agency, I believe the costs were about $30,000 for 2-3 minor variants of the same product.  Changes after that for modifications after certification were in the $5,000-10,000 range.  Even substituting inconsequential parts could cost quite a lot after the fact.  The emissions / susceptibility testing cost added more to that but I forget the total cost.

It is essential to bear in mind that changes will cost you and to plan ahead with potential second source components. Don't run it through agencies until you have thoroughly functional/ and pre-safety-tested yourself.  It is generally easier and cheaper to get it done up front vs. piece-meal later on.

9

Open Source Hardware / Re: ESP32 Ethernet, Wi-Fi & Serial Gateway

« Last post by selcuk on Today at 09:44:11 pm »

Looks nice!

Some questions/comments:
- choosing to use the bare ESP32 IC is a bold move, because that means you have to seek regulatory certification yourself for the radios. (One of the big advantages of using an ESP32 module is that they’re already certified worldwide.)
- why USB mini-B and not USB-C?
- what are the two different Ethernet port versions?
- the datasheet has a typo, the RTC crystal should be 32.768kHz, not 32.758kHz.

Thank you for your comments and pointing out the error in the datasheet.

I used micro USB since it is cheaper, and I have lots of them at my office. But USB-C is a good idea. I can use it when I make a second revision.

There are two boards with the same functionality in this project. One has components for a temperature range of -40 to +85 °C. That one has a more expensive Ethernet connector. The other board design is for 0 to 70 °C and I used a lower priced connector.

You are right about the certification, but I personally don't prefer to use modules instead of bare MCUs. Even I used it, I would need to get a certification for the whole product. I can say that the ESP32 Ethernet modules on the market are very susceptible to both radiated and transient emissions. The main goal of this design was having a robust ESP32 Ethernet module to use for my projects.

And there is another purpose. After I decided to do an open source design, I wanted to contribute more by not using a module and by doing the PCB antenna design from scratch for this board. ESP32 modules' PCB antennas are not that good, and I thought there was a room for an improvement.

10

General Technical Chat / Re: Post a picture of a cat!

« Last post by NiHaoMike on Today at 09:39:36 pm »