Recent Posts

1

Beginners / Re: Convert US standard 115V to International 230V

« Last post by tooki on Today at 02:07:47 am »

My favourite one was when it took several pages to explain why a capacitor connected to a generator doesn't increase the power consumption, ignoring the tiny extra I²R losses.

For what reason you're writing it in that way like I was claimed that capacitor will consume the power? This is false. I didn't claimed that.

No, the wording doesn’t say the power consumption is in the capacitor, just that you thought adding the capacitor increased power consumption in total. Which is something you stated in the thread over and over and over.

We could substitute “reading comprehension” for listening, and you just proved our point: you don’t listen, or in this case, read carefully. You’re seeing what you want to see, not what’s actually written.

2

Power/Renewable Energy/EV's / Re: SMPS input filter cut off frequency

« Last post by temperance on Today at 02:05:48 am »

Explanation and real world measurements included.

Cheers

3

Test Equipment / Re: Test Equipment Anonymous (TEA) group therapy thread : GPIB breakout board

« Last post by dazz1 on Today at 02:04:59 am »

Hi
I have modified the design to include the probe networks.  I decided to implement the full terminator/probe networks.  Two resistors and one cap on each probe are now fitted to the bottom layer.
I used discrete components because using arrays would have required a major pcb design change. 
There wasn't room for the capacitors without a significant increase in pcb size, so I will stack them with the 91k resistors.  The caps are probably not needed  for my use case, but easy and cheap to include in the design.

4

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by coppercone2 on Today at 02:03:04 am »

they are superior materials but they are difficult to make and expensive, some require a long heat treat process (72 hours glowing)

ceramic is expensive when its performance ceramics. when we have 1$ / megawatt hour electricity they will be really cheap

You know, guaranteed not to crack for no reason, because ceramic.

I think high performance 3d metal printing bringing down the cost of acceptable mold making (maybe) will cut some of the price off ceramic (press before sinter). then the other part is high efficiency furnaces and cheap electricity. I think the cost already went down some because of high end robotic inspection equipment for doing QC on that side of things.

mold making is like a giant problem. They need to be made of the toughest materials, require inspection and are very precise (to deliver pressure properly and uniformly)


AlN is synthesized by the carbothermal reduction of aluminium oxide in the presence of gaseous nitrogen or ammonia or by direct nitridation of aluminium.[22] The use of sintering aids, such as Y2O3 or CaO, and hot pressing is required to produce a dense technical-grade material.[citation needed]


Hot pressing. That means what, inconel molds and monel plumbing? $$$
that is the kinda tech aliens will have lol

pushing investment into big AlN manufacture for low priced materials would be interesting.

5

Repair / Re: Desoldering advice

« Last post by tooki on Today at 02:02:58 am »

You absolutely need auxiliary heat!

Think of it like this, assuming the original lead-free solder: you need to raise the joint temperature by over 200°C (ambient 20C, melting point 227C). Right now, ALL of that energy has to flow in through the soldering iron tip, and you’ve got a big board sucking heat away on all sides. Even if your iron can reach 450C at the tip, all this means is that you’re overheating one spot on the board, while still not heating the joint as a whole sufficiently.

Now suppose you use a small oven or a hot air gun at a gentle temperature (say, 150C) to heat the entire board to 100C. Now the iron only needs to increase the joint temperature by 130C. Or preheat to 150C and the iron only needs to add 80C to the joint. Those are MUCH more reasonable numbers, and mean you’re less likely to damage the board.

And for sure, use a bigger tip. Bigger tip = better thermal conductivity = lower tip temperature needed = less risk of board damage.

6

Beginners / Re: Why are thermal jumpers so expensive?

« Last post by tooki on Today at 01:52:46 am »

Hi,
Why are these Al Nitride thermal jumpers (SIZE 0603) So expensive (42p each in volume of 1000's.)

https://www.vishay.com/docs/60157/thjp.pdf

They're a niche product without much competition. That alone means they can charge whatever they want. I suspect they aren’t made in huge quantities, so economies of scale aren’t there.

I mean, an SMD FET with a copper pour could have that copper pour coupled to an 0603 NTC (via a thermal jumper) and temperature regulation of the FET get
done very directly like that. This could pave the way for the SMD FET revolution in SMPS's (ousting of thru hole TO220 FETS)

Uhhh… PCBs, even with multilayer copper pour, are terrible heatsinks compared to, well, heatsinks. Even so, with modern low-Rds(on) MOSFETs that don’t need much cooling to begin with, we are seeing more and more SMD versions. They can also be coupled to heatsinks.

You may even have heard of these things called “CPUs”. They’re these so-called “computer chips” that form the “electronic brain” of your computer. Most of these have been surface-mounted for years and years now (since most computers now are laptops, which don’t normally use socketed chips). And these cyber-cerebra often dissipate a lot of heat, which we manage to remove despite not being in TO-220 packages.

Also, this aluminium nitride , has W/mk of 170, thats great considering alu is 240,  and the best gap pad is around 7W/mk.
So why arent people using this aluminium nitride for SMPS enclosures? (rather than plastic)

So you want your chargers to be enclosed in a very expensive ceramic? That sounds like a grand idea… /s 

Or you could use, ya know, aluminum, and just insulate it. There are thermal pads with very much higher W/mK than 7. I bought one on DigiKey with 1600W/mK.

7

RF, Microwave, Ham Radio / Open-source Off-Grid Phone Network

« Last post by jonovid on Today at 01:50:27 am »

Meshtastic   is an open-source mesh network long range off-grid communicator
ESP32 is a feature-rich SoC with integrated Wi-Fi and Bluetooth connectivity for a wide-range of IoT applications.

8

Projects, Designs, and Technical Stuff / Re: How is a motor run capacitor sized?

« Last post by aroby on Today at 01:47:51 am »

What is the exact size?  Especially diameter and lead spacing.

12mm diameter, 38mm long

9

Test Equipment / Re: Siglent SDS3000X HD and upgraded SDS1000X HD

« Last post by DaneLaw on Today at 01:44:05 am »

10

Beginners / Re: Convert US standard 115V to International 230V

« Last post by radiolistener on Today at 01:42:38 am »

My favourite one was when it took several pages to explain why a capacitor connected to a generator doesn't increase the power consumption, ignoring the tiny extra I²R losses.

For what reason you're writing it in that way like I was claimed that capacitor will consume the power? This is false. I didn't claimed that.

We're talked how the power returned from capacitor to generator affects its mechanical rotation. And looking at that discussion now, it appears that I missed to clarify that I was talked about instantaneous power and my opponents are talked about average power and it leads to confusion.

Regarding to the power consumption, it is obvious that it will increase power consumption due to losses in the wires, because energy will flows back and forth between the generator and capacitor and of course it will increase power losses in wires in comparison with pure active load where power loss happens only once when power is transferred in single direction from generator to the load.