Recent Posts

41

Projects, Designs, and Technical Stuff / Re: What is the 'go-to' MQTT broker software for local home setup

« Last post by selcuk on Today at 12:20:23 pm »

The auth plugins only pull data about password and etc. from given tables. For a complete system with database and web interface, I think you should do your custom setup. I don't know a ready made solution.

For my project, I wrote a not-complex C application using libmosquitto and libpq. This app was a MQTT subscriber. There was a php web application as well. My app susbcribes to all topics of the devices so each sensor data arrives to it and then it stores them to database. Web app reads and writes only to database and it can read the saved sensor data any time user loads the page. In this scenario, you don't need and interaction between web pages and MQTT.

42

Beginners / Re: Bulk input caps and impedance

« Last post by strawberry on Today at 12:20:21 pm »

convert waveform to RMS power, that will produce heat within estimated timeframe
need to know resistors thermal resistance(long term dissipation) and thermal capacity(short term)
then calculate close enough temperature

can experimentally find hot spot temperature with IR camera

NTC wont work well when dissipated power is less than 1..2W

43

General Technical Chat / Re: Is LinkedIn worth keeping?

« Last post by artag on Today at 12:18:56 pm »

I joined some years ago, dumped it when they started to get a reputation for spam and worthless recommendations.
Haven't missed it.

IMHO personal contacts and scouting are the best ways to find a job. The vacancy websites are just full of recruiter spam jobs which always turn out to be filled when you ask. They just want you on their database and won't make an effort to find things quickly.

44

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

« Last post by pcprogrammer on Today at 12:18:26 pm »

2) I have 2 video capture adapters.  One of them is working, the other is not. It turns on when you twist or press the board in a certain way, but not always. Upon careful examination, I did not find any contact failure on the board.  Therefore, I want to compare both adapters on an oscilloscope. I want to ask: can I simultaneously check both adapters with both probes, connecting each of them to its own minus, or is this not possible?

As long as the 2 video capture adapters share a common ground you will be fine, but make sure the ground of the probes are connected to the same ground potential.

Are these video capture adapters USB devices? If so it is best to connect then to the same computer for performing these tests. Then the ground potentials will be more or less the same.  Connecting the probe grounds to the separate devices will cause ground loops and this might lead to incorrect measurements, but the scope you are using is not the most accurate either. 

45

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by mrisco on Today at 12:16:12 pm »

...You show signal that has 10ns period, measurements measure 20ns period, and Counter measure 140 Hz (should be cca 100MHz)..
Am I confused or what?

Just ignore that, it was noise at my desktop and the screen shows a little piece of a larger noise. So, the counter is counting anything.

46

Test Equipment / Re: Hacking the Rigol DHO800/900 Scope

« Last post by mrisco on Today at 12:12:42 pm »

Is your modified app fully functioning when installed? i.e., able to save screenshots, etc... 

Oh! I was on page 67 of this now 106 pages thread and saw a modification of the UI. So, I got down to work. I think that I just reinvented the wheel. I should have read some more pages, that could have made my job easier by working on what you have already done.

I had the same problems as Andybig had. My application is signed with my own development key, so it can't share the system user space. So, in the beginning if the application is installed normally and granted root access but not system access, it can't take a screenshot. For me it is not really a big problem because I use the webui to take the screenshots.

47

Other Equipment & Products / Re: Crimpin’ ain’t easy (or: best hobbyist crimping tool/system?)

« Last post by tooki on Today at 12:10:04 pm »

OK, I see why I didn’t find the original JST tools on Misumi: apparently, they’re “general purpose tools” and not the “dedicated tools” category I naively looked in…  (So far, I’ve found at least three categories which contain subcategories with crimp tools. What an awful, awful website, with respect to taxonomy.)

Anyhow, their prices for the tools are not low, so at 50% they’d be good prices, but not at full price.

48

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

« Last post by Aldo22 on Today at 12:09:38 pm »

I want to ask: can I simultaneously check both adapters with both probes, connecting each of them to its own minus, or is this not possible?

I don't know exactly what you mean.
The Zeeweii itself is not grounded (earth) when it runs on battery, but of course the two BNC grounds (minus) are connected in the oscilloscope.
Maybe someone else can help.

49

Projects, Designs, and Technical Stuff / Homebrew Lock-In Amplifier

« Last post by Picuino on Today at 12:03:59 pm »

Some time ago I bought the necessary chips to assemble a homebrew lock-in amplifier and I would like to assemble it and experiment with it.
Has anyone assembled the lock-in amplifier based on the AD630 that is circulating on the internet?
With which PCB can it be assembled with guarantees that it will work well?
Has anyone experimented with it and what interesting experiments can be done?
I know there are a lot of questions, but they can be summed up in just one. Can anyone tell us about your experiences with this instrument?


Homebrew Lock-In amplifier:
https://www.holographyforum.org/data/pdf/aa-Collection_a_k/aa-Laser/aa-lockin/Homebrew_lockin_amplifier.html
https://www.instructables.com/Lock-in-Amplifier/

More professional version:
https://physicsopenlab.org/2019/08/20/lock-in-amplifier/
https://www.ebay.com/itm/275596051897?epid=2282365081


What is a Lock-In Amplifier:
https://en.wikipedia.org/wiki/Lock-in_amplifier
https://www.zhinst.com/en/resources/principles-of-lock-in-detection
https://www.thinksrs.com/downloads/pdfs/applicationnotes/AboutLIAs.pdf
https://www.liquidinstruments.com/digital-lock-in-amplifier/

50

Test Equipment / Re: SDS800X HD - Issue disscusions - is it me, or the scope?

« Last post by eTobey on Today at 12:02:12 pm »

Another issue:
When missing the "+" or the button for resetting statistics, the measure menu opens. It is already too hard, to hit the resetting button. 
 

See picture.