Recent Posts

1

Computers / Re: M2 to IDE adaptor

« Last post by tooki on Today at 12:47:13 am »

That’s what I thought, just wasn’t 100% sure. 👍

2

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

« Last post by coppercone2 on Today at 12:46:26 am »

ok I will try it with 2 bjt before we make it into the manhattan project

I have TO220 sockets to make this easy

3

General Technical Chat / Re: Your pet peeve, technical or otherwise.

« Last post by calzap on Today at 12:43:40 am »

Incorrect use of “percent increase”.   Should be later value minus earlier value divided by earlier value times 100, i.e. change related to starting value.   So, if value was 100 and increased to 200, percent increase is (200-100)/100*100 = 100.  But can find it as (200-100)/200*100 = 50 percent increase.  Or as 200/100*100 = 200 percent increase (this one is commonly used for investment sales).  Or even (200-100)/[(100+200)/2]*100 = 67 percent increase.

Mike

So, what is your take on marketing claiming a % increase/decrease in temperature?

Gamer's Nexus went absolutely nuts at some manufacturers for saying things like a case had 15% better cooling and 5% lower temperatures.

He was like, YOU CANNOT APPLY PERCENTAGE TO A DEGREE!!!! and basically detonated.

Oh, you can correctly calculate a % increase or decrease in temperature.  Question is whether it has any meaning.  Suppose an object is 50C.  A 50% decrease in temperature brings it to 25C.   That 50C object is 122F.  A 50% decrease from 122F is 61F.  But 25C is 77F, not 61F!  A percentage increase or decrease in an intensive variable with an arbitrary zero isn’t all that quantitatively useful by itself.   There can be directional and ordinal comparisons.   A decrease is colder; increase is warmer.  Comparing two identical objects that are cooling from the same starting temperature, the one with the biggest % decrease in temperature got colder.

Calcs get a little messy if a % change takes the temperature through zero.  If an object is 16C and has a 50% decrease in temperature, that’s 16 x 0.5 = 8.  What about a 150% decrease?  100% decrease would take it to zero.  A further 50% decrease takes it to 16 x -0.5 = -8.

However, % decrease/increase in temperature can be used in calculations with other quantities to obtain useful results.   If the mass of an object, it’s specific heat, it’s starting temperature and % decrease/increase in temperature are known, then a potentially useful % change in its thermal energy content can be calculated.

Percentage changes in cooling can have useful meaning depending on how it’s calculated.  If 100 J per second was being removed from a source and now it’s 150 J per second, that’s a 50% increase in cooling, i.e. 50% better cooling.

Mike

4

PCB/EDA/CAD / Re: JLCPCB smallest possible label and text font size

« Last post by tooki on Today at 12:42:56 am »

Even 1mm text often comes out illegible, depending on the font. The silkscreen on low-volume PCBs at JLCPCB is often done with UV inkjet*, and the resolution isn’t that high, I suspect under 300dpi. I don’t think 0.75mm text height stands a snowball’s chance in hell of being legible. Even on a high-res true silkscreen that would be asking a lot.

If you can, make your label on the copper layer. The resolution of the copper layers is far higher than of the silkscreen layer. If you can’t do that, can you do it on the solder mask layer? That’s still better resolution than the silkscreen layer.


*inkjet printer using UV-cured lacquer/resin inks

5

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

« Last post by SiliconWizard on Today at 12:42:24 am »

Cascade several FETs. Yes I think it's been talked about before.
Then call Electroboom before you turn it on.

6

Repair / Re: Leader FG 1301 - Dirty switches

« Last post by Muett on Today at 12:40:35 am »

Needles to say, Deoxit brought it back to life.  Push button switches all work perfectly.

7

Computers / Re: Programm to show a filtered list of a csv file.

« Last post by SiliconWizard on Today at 12:38:02 am »

I dont write another script for a program that checks another program that checks my original program/software that i want to develop. Its a rabbithole...

Well, then don't. Do as everyone does in the software industry these days, do not check much, ship fast and see what happens. It may not always work, but it's good money.

8

General Technical Chat / Re: Chinese solder wire brands?

« Last post by Monkeh on Today at 12:37:20 am »

They forced seatbelts and airbags, too - surely they didn't need to do that?

"What about"-ism.

No, an example of changes which had to be forced to occur in a timely fashion. It just doesn't happen to support your position, so is rejected by any means necessary.

9

Test Equipment / Re: Accurate Low Amp Current Probe Advice

« Last post by KungFuJosh on Today at 12:36:26 am »

Here's the first test. 5ma/DIV, 1mA draw from ET, 10.4V on SPD.

I also took a screenshot of the noise between the ET and SPD with both powered on, but nothing active.

10

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

« Last post by tggzzz on Today at 12:30:44 am »

Ok I am just gonna try the basic one first that circuit in the picture looks very complicated , perhaps I will figure out why it was made when I see the deficiencies of the first one

The strengths and weaknesses of each circuit are clearly explained.

Just get TAoE and TAoE x-chapters. You won't regret it.