When I'm measuring voltage at high currents, can I just use a voltage divider with very high resistances? Same as earlier: I'm measuring a fuel cell output with a max of 18V and 75A

Folks, does anyone know where to look for NPS pipe fittings? Not NPT (tapered), but NPS (straight). It's for this flow rate sensor. I've spent half an hour with search engines, but couldn't find the right fittings. Which industries use NPS threads? Could anyone point me in a right direction?

@NickAlexeev Weird: "In contrast to straight threads that are found on a bolt, a taper thread(NPT) will pull tight and therefore make a fluid-tight seal" - en.wikipedia.org/wiki/National_pipe_thread

learn.adafruit.com/adafruit-keg-bot/install-flow-meter

A 7/16" UTS thread has almost the same specs as a 1/2" NPT/NPS thread -- Pitch 0.07142857" and 14 threads per inch(TPI) - The problem is the diameter though

On the NPT wiki page it does say that a 1/2" thread has an "Approximate total thread makeup, hand and wrench" of 7/16"

Searching for NPT stuff("1/2 npt barb female") instead of NPS gets some non-tapered fittings such as: ebay.com/itm/331146108484, ebay.com/itm/351107150919, ebay.com/itm/390962087472

forums.adafruit.com/viewtopic.php?f=19&t=48642

forums.adafruit.com/viewtopic.php?f=19&t=61950

The two forum threads above, yielded the following links. The people posting vouched that they fit: grainger.com/product/THOGUS-Female-Adapter-3XVT2, amazon.com/dp/B008TSRWXS

@MLM Weird, yes. I haven't come across NPS threads before.

As far as I understand, the NPS thread has a gasket. The male part squeezes the gasket when it bottoms out and creates a seal.

@MLM It looks like they are hacking an NPS male thread into an NPT female thread. I could try that too.

I appreciate your help with tracking down these fittings!

I think many vendors/people are listing their fittings as NPT when they are straight NPS. (from some of the pictures, it definitely seems that way)

@MLM That's plausible. The 1/2" NPT prescribes that 10 threads should be cut, but some of the parts that you've found have only 5 threads.

What concerns me, though, is that the proper NPS female has a gasket, but NPT female doesn't have a gasket.

morning

morn @jippie

@MLM Ah! But I think, I've found a proper one here. Rubber seal and all.

fluid-tight... unless of course, it is liquid helium...

someone please invent a replicator so I can just download a scope...

good morning! I need help with selecting parts for PWM control of a 12V, 35 A resistive load.

so first of all - is anyone awake?

PWM will be generated by a 3.3V microcontroller, and I've picked the IRFP4004 as a low-side switch. Now 3.3V logic and this transistor won't go too well together, so I need a gate driver. This is what I don't have any experience with. What should I look out for?

@Christoph for playing around or doing something that should last a while? for playing a simple push pull+charge pump will work, for something that lasts any driver IC with the proper specs will likely do

It should last a while. What are "proper specs" in this respect? I really don't know much about driving MOSFETs and how their and the driver's characteristics play together.

@Christoph besides that you might want to look through some related questions on this site, look up your fets datasheet max V_th add that to the voltage you want to drive, add a bit, then thats the voltage you want to drive it with. make sure the IC can source enough current for whatever gate capacitance you need to drive. I would recommend you maybe simulate things if possible to get an idea of that those things do about what you want

@PlasmaHH By V_th you mean the maximum gate threshold voltage V_GS(th)?

@Christoph indeed

Hm...there seems to be only little magic involved, yet I'm hesitating to just give it a try.

@Christoph If your 12V supply is pretty stable, you can use that as your gate driver power supply. That's a pretty beefy FET, I'd say get a "4A" gate driver or more. Switching it at a high frequency will draw a lot of gate drive current.

Be careful that your gate driver IC you select isn't just 2 BJTs packaged together - some of the cheaper ones fall in that category. If you just need a part number, maybe the IXYS IXDN602/IXDN604 series? It's not the best with a 12V rail

Should logic ICs be socketed? I am building a one-off project which needs to last around 30 years.

@user60684 No

To elaborate, the chip isn't going to fail (unless you're doing something wrong), and adding the socket adds another point of failure (mechanical contact between the socket and chip)

And you should be using SMT parts anyways ;)

I'm somewhat amazed by the amount of thought that has gone into determining the appropriate length and diameter of a probe to represent the human finger when safety testing enclosures for accessibility.

@user60684 olin asked a question recently about stuff to take care of when things have to last long, maybe you find info there that is intresting

@ThePhoton I suddenly have an image of lots of bandaged chinese people in poor villages running around...

what is it with people that they pay more for things on ebay than they would pay for the new thing?

@W5VO My 12V supply would be an ATX PSU. The list of components I can get without too much hassle isn't huge, I've now picked the IRFP3306 (lower gate capacitance) and a MCP1407 to drive it.

@Christoph I found it sometimes being intresting to search on this site for such ICs and see what experiences/problems people had with it, if any.

@PlasmaHH I've looked around a bit and while that's certainly a helpful source of information, I'm having a hard time finding parts people have reported to work in a certain combination of parts I can buy, with the voltage/current I need

but reading Q and A certainly did help me pick something

@Christoph yep, thats almost an art... a lot of people have their list of standard parts after a while, even if others would fit better

Hm, what could I have lying around that I could use for breadboard "feets" ... must be 2cm high...

bottle caps

not high enough unfortunately... or what kind of bottles do you have? ;)

standard german PET bottles

yeah the caps are indeed less than 2cm high

~1cm in height...

use two!

hot glued together? dont know if thats so stable...

how stable does it have two be? you can also use a small screw

well, sometimes you have to push ICs with many pins quite hard, so... I want this one to last a bit longer than my last one ;)

you crushed you breadboard feet by pushing in large ICs? did you use corn flakes?

no, I crushed the last one itself... I wanted to pay the word tribute and glued it onto some wood, but it was probably too thin (or not enough supporting feet) so it broke apart

in that case I'd probably use a piece of thick plywood (15 mm or so), but seriously I've never managed to break a breadboard. are you talkng about those usually white, 15 x 7 cm solderless prototyping things?

ah well, good night! see you later

@Christoph yes, imagine you have like 16 ones with 800 contacts, all mounted (2x8) on some piece of wood... that is not thick enough