Recent Posts

1

Beginners / Re: Dimming signal 0-12V from microcontroller (logic level to 12V PWM)

« Last post by Zero999 on Today at 08:48:14 am »

I thought you said the dim input is 12V tolerant?

The ratio of R3:R2 is wrong.

A_V = 1 + R2/R3

You need R2 to be 2 ²/₃ times the value of R3 for a gain of 3.3.

Try
R2 = 56k
R3 = 24k

2

Manufacturing & Assembly / Re: Brief review of the Zhengbang ZB2520HL reflow oven (T-962A alternative)

« Last post by hp23 on Today at 08:47:46 am »

I agree. They're not great out of the box. Some post factory tuning is required. I'm getting good yields. 4 layer smts with some hefty inductors and plastic connectors. Still having no joy with the PC interface though (hint).

3

Projects, Designs, and Technical Stuff / a high side load switch made from n channel and p channel mosfet working princip

« Last post by oppel on Today at 08:41:30 am »

Hello, I did research on the internet to understand the working principle of the circuit you see in the image, but I could not find an article that explains exactly how the N-channel and P-channel MOSFETs used here work according to their transmission cut-off states. I would appreciate it if you could give detailed information about the working principle of this circuit.

4

RF, Microwave, Ham Radio / Re: fake MPF102s from AliExpress

« Last post by Solder_Junkie on Today at 08:40:56 am »

I would speculate that they are still fakes, but probably of the better side of the spectrum. I'm almost tempted to get some (mosfets, I think, as they're the easiest to test for basic parameters) and see how far the fake inductry has progressed .

It is usually not too difficult to find more modern semiconductors from a genuine source, so please don't undermine them by dealing with far eastern fake suppliers.

There is nothing worse than trying to figure out why something doesn't work, only to find the dodgy transistor/IC you fitted is the culprit...

My recent projects have included semiconductors from Mouser and hardware from CPC (part of Farnell). One item I bought that proved a waste of money was an Arduino that worked for only a matter of days... you guessed, it wasn't a genuine one. Lesson learnt.

SJ

5

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by 2N3055 on Today at 08:39:39 am »

Can the TSA do amplitude modulation?
Put in some AM at about 10% of the frequency.

It only supports a limited number of amplitude levels (I think 8 or so) for the the modulating signal, so it's a "stair step sine wave".
And the modulating signal is limited to 10 kHz.

EDIT: See also Erik's video: https://youtu.be/U2cw0bmuSLM?t=239

The TinySA supports 8-point interpolation, while the Ultra can muster up to around 128 points depending on modulaton frequency.

Ok, no problem.

I'm just wondering how the Siglent is cheating to get that display. The Rigol isn't doing anything wrong, it's doing the correct math for the limited information it has.

The original Signal can be reconstructed with much wider filters but they'll only work if the signal is perfectly periodic.

I was wondering what happens if the signal isn't periodic. It could go very wrong.

It is amazing how people project their own mentality to others.

There is no cheating. Just accept it.
It looks exactly the same if you single shot it.
That is your nonrepetitive signal.
It is just done right.

Why the other manufacturer's device doesn't show right? I don't know.
But it is them that, on several occasions, have shown bad reconstruction of data and cheating of all sorts...

6

Computers / Re: Format a 256GB pendrive with FAT32 using a windows 10 pc

« Last post by golden_labels on Today at 08:38:22 am »

I would be happy to join the crowd seeing this as yet another artificial scarcity attack. Or at least attribute it to the lack of thinking.

But in this case the explanation is well known and documented, and it is neither of the above. It’s a reasonable decision, which didn’t age well. The person responsible, Dave Plummer, gave the details.

Unlike with other fake limitations, Microsoft never prevented users from creating bigger FAT32s even with their official tools – only that single GUI tool got affected. Never profited from it. Never used it against anybody. By the time anybody asked, the limit became a de facto standard. By the time it became relevant to wider audience, memory cards were using exFAT.

Was the decision bad? No. Historian’s fallacy applies. And Plummer was still very cautious and generous setting the value to 32 GB. Remember this is 1995. Your internal HDD was 250 MB to 1 GB, which you would further divide into partitions. That was a time, when I sent a screenshot of a program reporting CPU to be 1000 MHz as a joke to a local computer magazine. And I would die from laugher, if anybody told me about 32 GB flash storage.

Was the decision invalid? Yes, I think so. The limit should have been 2²⁸ · 512, which is 128 GB, not 32 GB. Unfortunately Plummer no longer recalled his thought process when recording the video.

7

Test Equipment / Re: Choosing between entry-level 12-bit DSOs

« Last post by 2N3055 on Today at 08:35:33 am »

There are specific posts in this thread covering most of this, but a summary doesn't hurt.

Rigol Pros: HDMI, VESA mount, WiFi built in.

Smaller size, battery option, more accessible UI, easy/neat Wifi with web/ftp access to the 'scope...

Rigol can go to 100MHz (or 125MHz) but is severely limited by its sampling rate.

Nope. Rigol can go to 280Mhz measured bandwidth, and shows signal far beyond that.

I wouldn't leave it at that bandwidth for general use but it's there if you need it and it only takes about 10 seconds to switch the model.

There's also 225MHz, 200Mhz and 125MHz options.

The lower sample rate sounds scary but when you're looking at real-life signals with probes clipped onto wires? Not so much.

(And there's no problem at all with 1 or 2 channels)

Your pointed out that advantages are telling us that it would be better as a portable multimedia device.
Switching the device BW by constantly tinkering with system apps is not same as having device that simply works.
It seems to me that people that own DHO800 Rigol scopes are buying that device to play and tinker with the scope itself, not to use it. There are also people that would buy a scope to work on their projects and want scope to simply work. To each, their own.

And again with channels. If that is your argument then fine.
But that is a 2 ch scope then.
Because with 4 ch it is not working properly.
Or 4 Ch with 70MHz.
But you cannot have it both ways.

Difference is that "the other" scope actually does work as 4ch 200MHz BW scope.
At all times, no special conditions..

So one scope is simple scope with multimedia and tinkering "built in" and the other device is serious instrument, designed to work as proper measurement instrument, with no gizmos and frills.

One is for hackers/makers and people that like to play with things, the other is inexpensive serious instrument (within obvious limits of it's class) for people that need that.

8

Beginners / Re: 555 driver and Transformer questions

« Last post by xavier60 on Today at 08:33:37 am »

The 0.1uF capacitor could be there to resonate with the primary inductance causing damped oscillations of a more controlled voltage rather than a massive narrow spike.
There could be more going on than meets the eye. Although the vibrator is mechanically tuned, it might possible that the duty-cycle is affected by battery voltage resulting in some crude regulation.

EXTRA: I see a possible problem, the primary wants to resonate but the 2nd half-cycle is being clamped by the MOSFET's body diode, returning the energy back to the supply.

9

RF, Microwave, Ham Radio / Re: fake MPF102s from AliExpress

« Last post by shapirus on Today at 08:32:56 am »

almost all transistors on aliexpress are fake. It can be branded but remarked other type, old repackaged, or just custom made with unknown parameters.

I've noticed an interesting recent trend that the sellers started adding die pictures in the product listings like this:



I would speculate that they are still fakes, but probably of the better side of the spectrum. I'm almost tempted to get some (mosfets, I think, as they're the easiest to test for basic parameters) and see how far the fake inductry has progressed :).

10

Test Equipment / Re: Program that can log from many multimeters.

« Last post by HKJ on Today at 08:32:52 am »

Made some modifications in my Powersupply-Test and Battery-Test scripts.
No spectaculair changes, but added some checks.
Removed some small faillures.
Changed information in command window after finishing tests.

The zip file Is updated.

i found an error in the RND KEL103v2 definition.
When i tried to use the Battery Mode, TestController did not update the values, because a part of the parameters was missing in the UDP transmission.
I fixed it and the battery settings are working flawlessly now.

This will be included in the next release.

PowerSupply Test script with making BurnIn test after testing Voltage and Current depedence.
Test can be started with an Internal Resistance check.
See the graph.
First Internal resistance check.
Then Voltage - Current test.
Then BurnIn test.
In Result in Command Window.txt the results in Testcontroller Command Window.

The website Is updated.

Here are three updated definitions.

I added a few math functions to the HP / Agilent 3458A setup menu. (I needed the NULL / offset function):



Also I found a small bug in this definition. Checking my other definitions, I also found this small bug in the Racal-Dana counter definitions. So I updated those too.

All 3 will be update in next release.