Recent Posts

31

Projects, Designs, and Technical Stuff / Re: Sylvano ZeroSmogISH fume extractor - how to measure rosin fumes level?

« Last post by BrokenYugo on Today at 06:05:23 pm »

Maybe a pair of dust sensors?

If filter life monitoring is your primary concern looking at pressure ahead of the filter might be a better approach.

32

Microcontrollers / Re: STM 32F4 FPU registers and main() gotcha

« Last post by wek on Today at 06:03:29 pm »

The FPU is part of the processor core, so it's not like other peripherals. This is ARM's rules, not ST's.

So, if you don't enable it, and attempt to access its registers, the processor throws UsageFault (ARM® v7-M Architecture Reference Manual B1.6.3 Pseudocode details of FP operation). If you don't have UsageFault enabled - which is the default - then it escalates to HardFault.

JW

33

Test Equipment / Re: Difference between HP / Agilent 435A and 435B Power Meters

« Last post by johnk0gcj@gmail.com on Today at 06:02:18 pm »

Good question. I've had a couple 435A's over the years and had seen but never had 435's, and had
assumed that the difference was the interchangeable scales on the 'A'. However, I recently obtained
another 'A' model, and it has the non-interchangeable scale. At first I thought someone had swapped
knobs with a non-working 435 until I realized that it has the marker where it belongs, just above the
outside circumference of the scale. The two 435a's are identical except one is a 1415A prefix with the
old style range indicator and the other is a 1629A prefix with the interchangeable scales. Apparently
the difference is other than what I've been able to detect without getting inside. Maybe when I get more
curious I'll do an inside examination.

34

Metrology / Re: Solartron 7081 - Reference Circuit

« Last post by Ismsanmar on Today at 05:52:26 pm »

All of my statements were factually correct and easily verified. PTFE is an excellent insulator/dielectric when you go up in frequency, having lower losses than most other dielectrics, but that is irrelevant to an electrometer that operates at near-DC. Yes, the carbon layer in commercial electrometer cables tames tribolectricity, but that triboelectricity was a problem introduced by the PTFE.

PTFE insulated cable is popular for a number of reasons. The best justification is that it withstands high temperatures, which is great if you need to move soldered wires. With care, a wire can be desoldered, soldered somewhere else, then resoldered in its original position and provided you deflux afterwards, nobody will be any the wiser. Try that with any other insulator and shrink-back will make your interference obvious. I like PTFE for that property. But we should not be blind to PTFE's documented shortcomings. Just because it is popular does not make it ideal.

Remember that exist something called silicone wire, it doesn't shrink with heat, and that is used to insulate cables. Or kapton coated wire.

It's only used because is the best dielectric, anything more.

35

Beginners / Re: Fast snubber circuit for relay coil

« Last post by SteveThackery on Today at 05:47:51 pm »

Hence the guess work, all in an effort to help them, and simultaneously irritate you it seems.

Now, now, don't be nasty. I've said not one single thing that implies irritation. I simply did my duty to the OP and future readers by pointing out that everything after post #2 is answering the wrong question and will actually have the opposite effect than the OP wants.

I'm puzzled by the reactions to me pointing that out. Instead of "Oh, yeah, you're right about that - we should make it clear to the OP", I get lectured on thread drift followed by some hand-waving around protecting the switching element. Trust me, I'm an expert on thread drift! 😂

Check my posting record - I don't make a habit of posts like this. But on this one occasion I believe my point is worth making. I don't understand the reluctance to acknowledging that.

36

Metrology / Re: Solartron 7081 - Reference Circuit

« Last post by Alex Nikitin on Today at 05:47:28 pm »

My two cents: at room temperatures as in a lab, I prefer a quality polyethylene isolated triaxial cable (H&S) for my electrometer interconnects. I also had some good experience using PEEK isolated connectors for an electrometer input (PTFE was impossible to use in that particular application) and as long as the temperature is kept below 40-50C they work fine with no reduction in performance compared to PTFE isolated connectors, with sub-fA leakages. 

Cheers

Alex

37

Test Equipment / Re: $20 LCR ESR Transistor checker project

« Last post by Yuriy_K on Today at 05:46:16 pm »

I burned mega328_st7565 to the tester, and that is the only one which is kinda working except that the screen size doesn't fit

I really don't know what to do with the makefile or how to use it, looks like a compiling thing

Did some tests still the same problem with those uF's

Your problem is that you need to have some knowledge of programming and understand how to configure some parameters in the makefile.
Here I fixed the horizontal offset of the text displayed on the display...

Now about the value of large capacities. In the firmware you can adjust this value, but you must take into account that the readings measured at a constant current differ from the readings at a frequency of 100 Hz. At 100 Hz the readings are noticeably lower...

38

Projects, Designs, and Technical Stuff / Re: Can anyone help to identify an op amp

« Last post by magic on Today at 05:45:23 pm »

I tried to pull the op amp out but it broke. I think it's glued to the board.

Time for more radical measures

39

Beginners / Re: Fast snubber circuit for relay coil

« Last post by floobydust on Today at 05:40:11 pm »

Late here but the zener's required power rating is something to consider as well. 1/2W generally too small for the impulse, good discussion with scope traces https://www.eng-tips.com/viewthread.cfm?qid=426309
Other papers:
TE Coil Suppression Can Reduce Relay Life
TE P&B The application of relay coil suppression with DC relays sourcve of pic 13.5V applied to automotive ISO 55Ω (large 250mA) coil.

40

Dodgy Technology / Re: Grants for Warp Drive Designs.

« Last post by coppice on Today at 05:38:11 pm »

I check in on the ITER project from time to time.  Almost 20 years in and what really do we have to show for the $$$ spent?

https://sciencebusiness.net/news/iter-fusion-project-confirms-more-delays-and-eu5b-cost-overrun

Their website is here:
https://www.iter.org/

I think you missed the point of ITER. Numerous people have already got their PhD from it. Did you think it was supposed to achieve something else?