Recent Posts

1

Beginners / Re: Power supply multi-rail noise separation?

« Last post by paulca on Today at 10:14:37 am »

So... in the meantime (until I redesign a whole board) I have the battery and I have loads... and I have protoboard.

First test shows without filters of any kind, save an LM7815 regulator, the battery powers the current 16V single supply headphone amp... silently.  Of interest, it's also silent when connected to the rest of the apparatus.  Confirming the noise I am annoyed with is coming from/caused by/influenced by the power supply.

Next I need to see if I can power the digital audio box (STM32H7 based) from a separate LM7824.  It has it's own buck module capable of 24V and I don't want to drop too much linearly if I can avoid it.  The box pulls 200mA ish.

I might not need any filtering...  I doubt it though.  Something is going to pull all that USB ground garbage into the audio somewhere, I just know it.

Does this look sane? 


The right hand side I'm fine with, even without a darlington it will work.  It's only temporarily / testing.

On the CLC/PI filter.  I'm out of my depth.  If a capacitor multiplier is a "High school" level thing, inductors are definitely one level higher up from where I am.  I can't seem to get a straight answer it's always a cyclic this depends on that, which depends on that which depends on the original thing.  It seems to make sense of this, mathematically, we get into greek and I go blank.

It's not just impedence at a rising frequency, it's proper understanding on the impedence of the L and both Cs and how they interact.... with the variable load R throw in.  If you can get it to attenuate rising frequencies from as low as you dare, you are also likely to have to deal with the resoance of some random (calculable) higher frequency.

It's beyond me   I feel religated to stealing an example and YOLO or buying some cheap AliExpress module and hopeing it's worth bothering.

I'm presently looking for examples to pillage instead.

2

Test Equipment / Re: Vevor SDS1104 for first oscilloscope?

« Last post by Aldo22 on Today at 10:11:23 am »

Max Record Length: 20K is a bit low these days.

How problematic is the max record length?

I don't know if it's "problematic", some time ago even good brands had 2.5k, but there are better options today for little money.

Since I'm currently experimenting with something like this, I'll show you with my $130 Hantek.

In the first picture there is a 20KHz sine wave at 10us/div, with a 50ns pulse every second (1Hz).
If you trigger on the pulse, a thin line appears in the middle. But there is nothing else to say about how the pulse looks. (1st picture).

If you zoom in it to 50ns by turning s/div, you will see a very rudimentary pulse at 4k (2nd image).
But if you stop it at 8M (record length), you can see much better in the magnification what is going on with the pulse (3rd image).
The more record length, the more accurate the magnification. Just like the resolution of a digital photo.

That is one difference. The experts here can probably explain this better, as I am also a beginner.

3

Test Equipment / Re: Siglent SDS800X HD 12 bit DSO's

« Last post by ebastler on Today at 09:57:47 am »

What kind of signal measurement and analysis does that fact prevent or even make difficult?

None. But as mentioned before, and even more valid for an "upper midrange" scope costing up to 7000€:

Agreed, the slow-down does not really limit the scope's functionality. But the slow-down of the update rate is a little irritating every time I experience it. It just feels "wrong" to see the core data processing affected by what should be an entirely separate and transparent user interaction. It makes me feel that either the hardware just barely makes ends meet, or the firmware is not well-engineered in this respect. Either way, it does not instill confidence in the instrument.

4

Beginners / Re: display current on scope

« Last post by pdenisowski on Today at 09:57:06 am »

measure the voltage across a know low value resistor

this involves some math, also it will set common ground to point of resistor and will block other scope channels, right?

If your oscilloscope has so-called math channels (and most modern scopes, even at the hobbyist level, do support this), the math can be done directly within the oscilloscope.

And you are also correct that using a "normal" single-ended probe would require (or force) one end of the measurement to ground.  When current is measured by measuring voltage across a small, known "shunt" resistor, a differential voltage probe is usually needed.  Depending on the specifications, etc. it might be cheaper just to buy a current probe, although differential probes are often useful for many other things as well.

I did videos on both types of probes (current and differential)

5

Test Equipment / Re: LCR Impedance Viewer for Picoscope+Keysight+R&S Bode Plot Data (open source)

« Last post by Cykeltur on Today at 09:52:23 am »

ok so i have skipped the probe för the generator side, THANKS , then from the generator, I have tryed 2 options (like in the manual and in your revommendation):

option 1:
Gennerator to B probe "red" and then also from Gennerator thru the ref resistor (120 ohm).
on the other side of the Rref I have the A probe"blue" and also from the other side of the Rref i have connected the DUKin.
then thru the DUK to DUKout, to GND clip on proBe A and B.

same result :-/

then i have altso tryed the  ;
option 2:
Gennerator to A probe "blue" and then also from Gennerator thru the ref resistor (120 ohm).
on the other side of the Rref I have the B probe"red" and also from the other side of the Rref i have connected the DUTin.
then thru the DUT to DUTout, to GND clip on probe A and B.

odd result :-/

the DUT has red and black cables in the picture, same as before,



   

6

Test Equipment / Re: Vevor SDS1104 for first oscilloscope?

« Last post by Muttley Snickers on Today at 09:51:11 am »

well, if you need 4CH:  go for the Siglent SDS1104 -- best bang for the buck   

Was....Now SDS804X HD is.

I would normally agree but also anticipate some of the current Siglent SDS1104XE owners upgrading to the newer SDS800 series which should inturn increase the number of earlier scopes available in the second hand market.

If the price is right then a used SDS1104XE in good condition would still be worth serious consideration particularly for somebody on a budget. If the OP is not in a desperate rush for a scope then this would be my recommendation, cheaper than new and far superior to what they are currently considering.

7

Projects, Designs, and Technical Stuff / Re: DIY Digital Caliper

« Last post by ali_asadzadeh on Today at 09:49:01 am »

Hardware - the footprints for the t-scale and sensor and also gerbers and schematics

Thanks for sharing, But it would be nicer if you could share the Kickad files for schematics and PCB, since We can modify it easier.

8

Beginners / Re: Replacing SRAM IC with Flash

« Last post by SeanB on Today at 09:48:09 am »

Use a larger FRAM device, like FM28V100, though you will need to make a small interface board to interface the 32pin SMD to DIP28. This gives you the option to add in 2 jumpers, allowing you to have 4 images in the FRAM, each totally separate.

9

Test Equipment / Re: Magnova oscilloscope

« Last post by Antonio90 on Today at 09:44:53 am »

Maybe more information can be squeezed from it.

They claim a very good usability with the encoder on the right side and connecting the probes on the right side.
So it is only made for right handed people? I am 101% left handed and can not imagine to use
this scope because my arm will hide the text at the encoder and the probe cable is to short when it is
connected to right side.

Olaf

Since the scope does not have any other buttons, it should not be too difficult to enable simple screen rotation. At worst the channel numbering is then upside down, but i would think you should be able to re-order them in software as well.

The probes on the right side can indeed be a problem for left handed people. Right handed too, if you have to move them to the left to measure something. I'm not a fan TBH, and I don't think BNCs are on the bottom for nothing, it's actually better for usability, and what we find on Magnova, some Micsigs, and all(?) handhelds is a compromise of the form factor. (For bench use)

As for the encoder and touch, I'm not sure. I have test equipment on the left side of my bench which I often use with the left hand without problem. Pushing buttons/screens or rotating encoders is not really hard work for the offhand IMO.

Rotating the screen would mean removing and reattaching the stand. We don't know if that is supported, and I doubt it. For starters, the handle is integrated in the case and would likely block the procedure. Cooling is passive too, and convection does play a fundamental role, as opposed to forced ventilation. I don't know if putting it upside-down would affect the thermal design, though.

10

Projects, Designs, and Technical Stuff / Re: Precision Load Cell (Wheatstone Bridge) Simulator

« Last post by floxia on Today at 09:40:43 am »

How did it perform? I am considering to give it a go!