Recent Posts

21

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

« Last post by IanB on Today at 02:32:13 pm »

According to the OP, the two power supplies are the only mains loads. The reason for the 20 A requirement was unclear, due to an earlier designer who has now left the project. It may simply have been a very conservative design.

These PSU can be used directly. But this is just 750W power consumption.

It is 750 W output power. Allowing for power supply efficiency the input power is closer to 900 W. But once again, this was covered earlier in the thread.

There is also another possible issue which is critical for medical devices, even if he using PSU which all are compatible with all mains standards, it still needs to be tested with both mains frequency. Note that the mains frequency has leakage through PSU in a form of a ripple and/or interferences and can affect equipment functions, especially if this is device which uses sensitive measurements.

For example precise ADC can have configurable rejection filter which can be software configured for 50 or 60 Hz depends on user environment. And it needs to be taken into account very carefully especially for medical devices (which is the case for topic starter question). And this example is not abstract this is example of a real case for medical devices.

There is a mains input filter in the design. Described earlier in the thread.

22

Beginners / Schumacher 5212 A battery charger

« Last post by cmvalerius on Today at 02:26:44 pm »

Both battery clamps fell off and I’m not sure which is positive and which is negative
One goes to circuit board, one goes to small white plug in? Can anyone help?

23

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

« Last post by KungFuJosh on Today at 02:26:36 pm »

If you do the equivalent of using a hammer to insert screws, is it surprising that the results are sub-optimal?

OTOH "Hammer Drive Screws" do exist. 😉

24

General Technical Chat / Re: Is LinkedIn worth keeping?

« Last post by tom66 on Today at 02:22:48 pm »

I maintain a LinkedIn account but rarely contribute.

I have gotten all of my previous jobs through the platform, besides the very first one, so I regard it as being useful from that end, but it is mostly recruiter spam these days.

25

Test Equipment / Re: UNI-T UDB3000S Series: UDP3305S / UDP3305S-E

« Last post by pope on Today at 02:22:13 pm »

Looks like the increased the prices. I was about to pull the trigger but now I'm gonna have to look for a different brand. Oh well...

26

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

« Last post by ebastler on Today at 02:21:06 pm »

I don't see that as much of a problem in practice, especially if you're aware of it. Four simultaneous 200MHz signals aren't easy for hobbyists to find. It's really easy to drop down to two channels if you're in doubt. You'll probably see a difference on the Siglent, too, if it's anything more than a simple sine wave.

If you're always working at 200MHz on four channels then you need a better 'scope than either of these. Probably active probes, too (if you're using probes).

It's enough to have one 200 MHz signal, which you need to observe in context with two other (potentially lower-bandwidth) signals. Not that exotic a requirement for those who decided to get a 200 MHz, 4-channel scope. On the DHO800/900, with only 312 MSa/s per channel, you will be out of luck.

27

Beginners / Re: Switching a 3KW (240V) immersion heater: Solid state or mechanical relays?

« Last post by IanB on Today at 02:19:35 pm »

It's an LED downlight with a 1m power cord attached to it.  So you install it into your ceiling and then... ahhh... WTF?

My garage is fitted out with switched plug sockets distributed across the ceiling. I was therefore able to buy replacement light fixtures fitted with mains plugs, and just plug them into those sockets. Having switched sockets for lighting is a common thing in the USA.

28

Programming / Re: Linux Dependency Black Hole

« Last post by shapirus on Today at 02:17:05 pm »

I also think things are getting worse. The reason are all those pesky new/better/wonderful ways to install software... that are full of shit. They don't want to learn how to create debian packages, or think they will make some money going that way, or fame/glory/whatever, so they have to invent the wheel again and again. But, while apt is almost the perfect wheel, those new wheels, well, not so much.

Apt is almost perfect, yes, but only as long as you install the software available in the distribution's repositories and, ideally, don't mix the distro releases (that can be done too, but requires experience and understanding).

The core issue with, almost universally, linux package management, is dynamic linking. Once you want to install something that was linked with a library that is not (or no longer is) a part of your distribution, you're screwed. That's where hell begins. It's good if there's a source .deb package: you can usually build a binary package from it using dpkg-buildpackage, and it will be linked against your available libs, and will install just fine. It's worse when you have plain sources. It's terrible when you have just binaries linked against libs in a 5 year old distro.

This is where packaging systems like AppImage can be helpful: they contain statically built binaries with no external dependencies. They will still work in 20 years just like they do today (provided it's the same CPU architecture), unless they depend on some specific kernel calls, which is not typical for general userspace apps. Good luck trying to run anything built for any Linux distro in 2005 today, unless it's a static binary.

I can see why software developers want to bundle their binaries as AppImage: spending time to learn how to build a gazillion different packages for a gazillion of different distros, not to mention another gazillion of their releases, would be insane. Why do that if you can build a universal package (actually several: by the number of target CPU architectures) that will be guaranteed to work on any linux distro?

Linux packaging is perfect as long as you stay strictly within a given distribution's ecosystem. Once you try to take a step outside (and you will, unless you have a purely academical interest in it), it becomes a nightmare.

29

Test Equipment / Re: SDS800X HD Bug Reports + Firmware

« Last post by eTobey on Today at 02:16:28 pm »

Another little issue:
The timout counter for closing the menu is not restart, when a sub menu settings is choosen. At least on cursors menu and search menu, and i guess on every menu.

Not a big one, but still annoying and confusing.

30

Test Equipment / Re: SDS800X HD Bug Reports + Firmware

« Last post by eTobey on Today at 02:14:28 pm »

Zoom function not working properly after loading mask:
Creating a mask and loading breaks the zoom function. See picture.

Also:
Creating a mask does not show the view that was set up for it.

I really would like that this feature "would" work with the zoom.

It does work.
You did not set it up properly.

You missed a little detail: i made a custom mask by hand.