shunts

I almost always put a spot for an inductor or resistor on power inputs. (Thinking mostly about LP filtering.) Then when testing, most of the time it's not needed so I jumper it out. (Through hole.. so an easy jumper.)

I found a "stash" of KOAspeer current sense resistors in an x-employee's drawers. Which is great because we don't stock very many low ohm resistors.

George H.

I always add a ferrite or 0-ohm jumper on the input to every supply.

So, you use these posts for your memory bank?

Low ohm surface mount resistors have gotten common and cheap in recent years.

Yesterday I needed to know the three output currents from a custom dc/dc converter. Luckily it has output filter inductors, 120 mohms each, so the current was easy to measure.

I designed this in 2002 and it's still in production. It's the timing controller for a DUV laser.

But nobody can make the transformer any more

because Magnetics quit making the 12-pin header. I've got to redesign it somehow.

Custom magnetics are an enormous PITA.

Not really, but I do like to discuss electronics. If anyone's interested.

Looks quite a bit like the transformers I've seen for the DC-DC supplies in VFD displays... Might have been a Keithley 2000, among others...

The problem is the weird header, with 12 pins on 3mm centers. We may have to mold or machine a new one. Or redesign the main board.

can't just use a piece of pcb?

castellations for the connections, or maybe just a hole and the wire also becoming the pin

-Lasse

We did machine one from FR4

and I wound one transformer myself. I assume real transformer people would do a prettier job.

Those round pins are not ideal, because the wire tends to slip off. Square or ribbed pins would be better. Maybe there is some way to do it with just a PC board, no pins. The pins are a nuisance. Gotta think about that. I have seen inductors that use the wire as the surface-mount connections.

I used Beldsol (thermal strip) 28 ga wire, which was a little stiff. I might try Litz, just because it would be easier to wind.

Incidentally, Amazon sells Thermaltronics Metcal-compatible tips, cheap. They seem fine. I guess some patent ran out. I had to get some high-temp tips to solder that wire.

Den onsdag den 22. juni 2016 kl. 22.36.44 UTC+2 skrev John Larkin:

yeh stick the wire through a hole and bend it around the edge

-Lasse

Did you ask XFMRS (XFMRS.COM)

They can do almost anything custom, but maybe you don't have the volume for a custom design (minimum 50k)

Cheers

Klaus

Turrets?

Cheers

Maybe something like this:

I could machine a piece of FR4 with 12 fingers sticking out. Wrap the transformer leads around the fingers and then tin them. It wouldn't be especially planar and I'd have to be careful about shorts.

I hate magnetics.

We've noticed. Magnetics is like everything else in electronics - it gets complicated if you want to do it right. Magnetics does start off fairly complicated, but can give stunning results if you get it right.

Is there a good negative rail sense amplifier chip around these days? I guess I can just use a 'single supply' op amp and a transistor. Telemetry is often useful.

--sp