Recent Posts

1

Beginners / Re: Blocking Phantom Power 48V from Audio output

« Last post by BennoG on Today at 12:15:39 pm »

yes you can, I would also add a extra resistor of 100k or 220k to the ground after that to discharge the capacitor.

However you need to double the capacity of the 22uF to 47uF or something like that, because capacitors in series act the same as resistors in parallel.

Benno

2

Buy/Sell/Wanted / Re: FS: Affordable DMM Checkers: AC Reference, DC Reference, OHMS Reference, etc.

« Last post by tggzzz on Today at 12:13:37 pm »

If you limited the claimed to, for example, "...verify the function of 3.5 digit Digital Multimeters", then the points wouldn't even arise.

What you claim here (or "elsewhere") is irrelevant; what you claim in the advert is what matters.

This is basic measurement theory. While you need higher resolution than the manufactured reference to measure its calibration error, that same calibration reference can then be used on on lower resolution instruments (assuming it is stable).  If you only work in mA, you do not care what is going in pA.

So a lot depends on claims for where it should be used.  And the reliablity of the maker.

FWIW, I bought one of the current and voltage references from AliExpress.  It includes a sketchy paper claiming the actual values as measured by some reference down to the 7th decimal point.  Turns out these measurements were within a couple counts on my Fluke 45, Fluke 8842, HP 358a and Keysight 1252.

Have no idea why I bought it since all my instruments already agreed, but it was cheap and I am a measurement junkie (work down to 500 micro meters).

Yes, repeatedly.

You bought it for fun. The only surprise is the degree of agreement.

But, as you know, it is relatively cheap and easy to get all your instruments to agree with each other. It is much more difficult and expensive to get them to agree with two other people's instruments

3

Test Equipment / Re: New Zoyi multimeter+oscilloscopes - ZT-70xS, up to 50MHz/250MSps (nov 2022)

« Last post by lazalem on Today at 12:12:44 pm »

Good Day!

Just want to know if ZT-703S is a good multimeter+oscilloscope for a hobbyist like me.  I am coming from a DSO150.  Which is a better buy among these:

Zoyi ZT-703S ~ 37.80USD (New)
Owon HDS242S ~ 74.16USD (New)
Owon HDS2202S ~ 78.07USD (Used)

At double the price, does the owon variants have better features, accuracy, reliability?


Thanks!

4

Repair / Re: Rigol DP712 Output Shorted; Fuse? / I Screwed Up

« Last post by Harry_22 on Today at 12:06:36 pm »

Dear Zanfar, unfortunately your power supply does not allow the direct battery connection.
No one could have foreseen this.
The fact is that the capacitor is installed at output. It is discharged through thyristor when the voltage is removed by pressing on/off button. When you connected the battery you voltage obviously was off and current passed through the thyristor. The swelling of thyristor case shows that the current was very large.
This can be corrected by installing an external diode between PS and battery (see scheme below).
I can't understand only the function of p-channel MOSFET.

5

Beginners / Re: Automatic golf ball dispenser

« Last post by BTO on Today at 12:05:33 pm »

Hay guys, sorry it took so long to respond, I went out to get some parts.

What there is left to right

Battery pack
Something that I don’t know
Relay switch
A timer
A vibration switch
Solenoid
And an arduino uno
Plus plenty of bits

I think I have enough to create something. But as mentioned about I want the vibration switch to trigger the solenoid. I’d like connect this to the T so that when I swing at the ball it triggers a new ball to load.

The thing that YOU DON'T KNOW is an "MB102"  POWER INTERFACE MODULE.
Basically i'ts a regulated power supply for your breadboard.
Plut it into your breadboard and it'll stretch from one side to the other all the way.

it has 2 channels so it has the ability to provide one power rail side of your breadboard with a certain voltage
and the ability to provide the other power rail side of the breadboard with the same voltage or another voltage

the way it works is... You'll input , via the jack 6.5V to 12V, most use a 9V Battery here
and it supports a regulated 3.3V or   5V on the output, and the USB can also be used as an output

so yeah.. it's a power supply

6

Projects, Designs, and Technical Stuff / Re: role of optocoupler for biasing drain of amplifiers

« Last post by xvr on Today at 12:04:42 pm »

Your overall schematic is very over-complicated. You need just P channel MOSFET, one NPN bipolar transistor and a couple of resistors.
I will draw schematic...

All resistors values are taken approximately.

Q1 - your power MOSFET. Should have DrainToSource breakdown voltage > 20V. GateToSource also >20V. RDSon will determine voltage drop and power dissipation on MOSFET.
Q2 - any NPN transistor with CE > 20V and high enough Ic (100mA or more will be enough) - it will define turn on time of schematic. R2 limit Ic of Q2.
R1 used to discharge Q1 Gate, it will determine turn off time.
R3 determine Ib of Q2. Should be low enough to ensure Ic (with minimum h21e of Q2

7

Programming / Re: Linux Dependency Black Hole

« Last post by xvr on Today at 12:02:49 pm »

It is 28 of .c and .h files. I wanted to put breakpoints to trace through the math which is meandering  over at least 3 of the .c
And the headers are all mixed up hard for me to follow I think due to multiple versions over 10 years.
Can all that be done in eclipse and gdb?

Yes, absolutely.

Eclipse is an IDE that use gdb for debugging, so you need to deal with gdb only.

First of all you need to build project. What build system is used in it? Can you see any of these files at top level?

Makefile
configure
CMakeLists.txt

8

Projects, Designs, and Technical Stuff / PCB humidity measurement circuit design

« Last post by strawberry on Today at 12:00:09 pm »

how to design spaced PCB tracks to measure air humidity with +/-10% accuracy
something that could work atleast with one dual OP

9

EEVblog Specific / Re: EEVblog 1612 - Siglent SDS1000X HD 12 bit Oscilloscope Teardown

« Last post by rf-loop on Today at 11:59:16 am »

There seems to be another plastic film on the surface of the screen (?). Apparently a residue left on the surface of the screen during installation, and then the film marked with a red ribbon was put on top. Please check  it. Surface need look same half matte as SDS800. Least I have not seen this glossy surface  in SDS1000XHD what can see in your video.

10

Security / Re: Microsoft repackages apps with a telemetry .NET wrapper

« Last post by tooki on Today at 11:57:25 am »

Of course corporations want to make believe that their spyware (ahem, "telemetry") is the equivalent of a usability study, but it plainly is nothing of the kind. Collecting statistics—on which buttons are clicked most often—doesn't yield any useful information if there is no experimental control. Data without a control is just worthless junk (see most papers in econ and nutrition for examples).

I worked in usability for years.

No, telemetry is not a substitute for usability studies, it is complementary to them, because they show real-world usage, which is often quite different from the studies. As for the statistical significance, it isn’t perfect since some users (which are likely to be more tech-savvy ones) opt out, but due to the sheer scale, it still produces tons of useful information.

I don’t know how you would make a control group for this; it’s not comparative analysis. It’s simple quantitative data: what gets used the most, and what sequences get used.