Recent Posts

71

Repair / Re: Repairing traces on a circuit PCB

« Last post by inse on Yesterday at 10:59:01 pm »

The photo doesn’t reveal too much detail, but if you can measure the width of the former trace you can calculate the cross section and select a wire accordingly or simply use whatever is at hand.
In case the trace was made as fusible link, you will never match the original behaviour.
It’s botch work anyway, but that’s ok if you keep it in mind

72

Projects, Designs, and Technical Stuff / Re: high voltage current source (mirror)

« Last post by coppercone2 on Yesterday at 10:58:34 pm »

Well its for measuring the voltage drop of a passive component I don't care if its high or low side if thats what you mean? I.e. it has to be transistor supply side for simpler implementation? That is more then OK


I am not sure what you mean by the 4-20mA loop. I was just thinking about this from the perspective of a simple textbook current mirror (there is many types with varying amount of transistors). I don't know which would be appropriate to analyze for this idea.

73

Projects, Designs, and Technical Stuff / Re: high voltage current source (mirror)

« Last post by PCB.Wiz on Yesterday at 10:57:49 pm »

Like this. I bet something bad would happen to the lower voltage supply though without more parts

If you want a grounded load, you are looking for a current mirror and a lever shifter.

Standard current mirrors do what the name says, they take a current fed to a common rail and reflect that using the same rail.
That means a high side load.

If you want no external low side power, then the circuit needs to power off the low side current source (see 4-20mA current loop designs for ideas)

74

General Technical Chat / Re: Chinese solder wire brands?

« Last post by tooki on Yesterday at 10:54:42 pm »

See the screenshot in my post above.  I can't buy leaded solder from any of the European vendors.  I'm sure I could buy it from China, who famously couldn't give a toss about EU regulations.

I know the European vendors cannot sell to consumers. That’s why I said to try buying from a US vendor like DigiKey or Mouser.

RS and Farnell are both UK-based.

75

Other Equipment & Products / Re: Suggestion for wire stripper for small gauges

« Last post by coppice on Yesterday at 10:54:37 pm »

The stripmaster lite is certainly not in the $30 ballpark however. It costs $100 and is probably worth that (nowadays). When I purchased 10 years ago, it was closer to $40.

You sure about that? I remember looking at the Stripmaster products nearly a decade ago and finding that the Lite cost about $100 and the big ones (especially the “custom” line) being significantly more than that, like $300+.

The Stripmasters used to be quite cheap. I've seen professional wire-men using a variety of tools for stripping fine single core and stranded wires for various kinds of electronics, but the Stripmaster has been the most common. Especially in defence work, where the cables all have to be temperature tolerant, and thermal strippers don't really cut it. There have been quite a few clones over the years. Some have been just as good as the original, while others are junk.

76

Computers / Re: Compiler Design at Cornell

« Last post by abeyer on Yesterday at 10:53:23 pm »

Information-dense exact notation does have its place: when that knowledge and understanding is applied, either in further science, or to solve problems or prove results in relation to that knowledge and understanding.  It should be built either as part of the learning process (but always secondary), or afterwards.  If you disagree, consider why learning Standard Chinese is easier if you learn Hanyu Pinyin first.

While I don't disagree with the premise that it would be easier to decouple learning the notation from learning the concepts... given the context of this being something that would be taught as an upper-level undergrad or graduate course, there's also going to be an expectation that students are at least reading and engaging with academic research, if not doing their own, and being able to consume the notation is pretty much table stakes there.

This style was never intended to maximize efficiency in learning, but rather for communication among the learned. And even there, I think it's debatable to what degree it's actually more efficient vs just customary and expected (and a bit of a shibboleth.) But either way, someone getting started in the field has to at least learn to read it, and trying to buck the trend and write in a different style isn't impossible, but is definitely a risk. I've seen people do it, but the ones who succeed tend to be people who have really good research content to start with, and are exceptionally good communicators and writers of prose on top of that. Getting to that level if you aren't already might be even more difficult than just learning the notation.

77

Other Equipment & Products / Re: Suggestion for wire stripper for small gauges

« Last post by Analog Kid on Yesterday at 10:53:23 pm »

Wow, that was a great deal indeed!!

So maybe my quest here isn't so ridiculous after all, eh?

78

General Technical Chat / Re: Solar frickin' Radweg, Erftstadt/Liblar (Germany)

« Last post by SiliconWizard on Yesterday at 10:53:21 pm »

Oh no, Solmove went out of business on March, 25th.
Now, I didn't see *that* coming 

Nobody did!

79

General Technical Chat / Re: Chinese solder wire brands?

« Last post by Monkeh on Yesterday at 10:51:01 pm »

I can't buy leaded solder from any of the European vendors.

You appear to have tried.. one.

You could also just try getting some decent lead-free..

The same regulations apply to all of them!

But aren't implemented the same way. You may well be able to convince some of them to sell you some.

I hate using lead-free - the iron needs to be stinking hot, it doesn't wet the surfaces as well as leaded, and generally produces poorer joints.

Oh, another 40C or so, terrible. Good flux wets fine (I have some which will strip the plating off cheap parts), and the joints produced are just fine. I doubt you could tell the difference between my 60/40 and SN100C by eye without side by side joints, and you won't find any difference electrically or mechanically which matters.

If it was any good they wouldn't have needed legislation to ban the leaded, would they?

You're proving exactly why change sometimes has to be forced.

80

Repair / Re: Repairing traces on a circuit PCB

« Last post by forrestc on Yesterday at 10:49:02 pm »

If they're only a couple of mm in width, you're probably looking at around 4A through those traces, absolute max, ever, even with thicker copper.

I'd just use something like 18AWG wire to repair them which is far in excess of what you need.  You mentioned that these went to the MOV which burned up.  One other option is to just use the leads from the replacement MOV (assuming through hole here) to connect to the appropriate pads.  That is, don't trim the leads, just bend them over to attach to the input pads.