Recent Posts

Pages: [1] 2 3 4 5 6 ... 10 Next
1
Beginners / Re: Mains Decoupling Capacitor
« Last post by Andy Chee on Today at 02:47:50 pm »
Not ESD.

More likely rudimentary EMI/RFI suppression.

2
But why it picked up FM signals which lies in 101.1 Mhz? i have never seen something like that before... also the picked up signal was pretty clear...  i forgot to take a video of it happening :palm: also it only worked at that time
The op-amp doesn't need to oscillate at 101MHz to pick up an FM station.

What's happening is there's a tuned circuit somewhere, which is resonating at 101MHz. This is being rectified by a PN (diode) junction in your circuit and amplified by the op-amp.

It's an amplified crystal radio. Normally crystal radios are known for AM (Amplitude Modulation)  but they can work with FM (Frequency Modulation). In your case, the tuned circuit will have a sharp peak, so the amplitude of the resonance will change, as the frequency of the signal changes, resulting in amplitude modulation, which is being rectified.

Here's an article about FM crystal radio, if you're interested.
https://electronbunker.ca/eb/FMCrystalSet.html

Going back to your problem. It's probably lack of decoupling and poor layout. The low level signals should use screened, preferably twisted pairs. Also try adding ferrite beads to the outputs of the power supplies.

The schematic of your output stage also isn't clear to me. Please use proper symbols, rather than just boxes.

yeah i also figured it out. it was the power amplifier not the opamp. I was actually making a 30 watt class ab amplifier that could run on single supply. but the problem is my phone cannot run it. needs a pre amp. single transistor preamps don't work with this poweramp. actually the power amp circuit is coppied from a random youtube video. also it was the only circuit that could be any loud otherthan the overheating ones. also the video claimed it could give out 50 watts which i dont think so.. on testing it that circuit could only give out 5 watts...
3
Quote
kreyren on 29 March 20, 2024
Quote
DiTBho on March 20, 2024
Just checked, the pinetab2 uses the Rockchip RK3566 SoC

Afaik the reason why OLIMEX didn't provide the RK3399 and RK3566 is that they were very unreliable software-wise (afaik they release the chip and then rely on the community to mainline them while not providing sufficient amount of documentation?) and tsvetan not wanting to support that as the resulting mainline is often very problematic and takes long time to get implemented in a way that is acceptable in industrial settings (OLIMEX's main focus)

For me in terms of arm architecture only use Cortex A7/53/55 and consider everything else garbage due to the CPU vulnerabilities, but i plan on supporting all chips as long as the required docs to make boards for these are available or unless someone wants to do the adventure of reverse-engineering them and contributing that (that's what the SOM management is meant to be for)

This is one of the public responses, which explain the reasons for the choices made.
I'm a bit perplexed, because it seems like it's always the same problem regarding software development, documentation, etc  :-//
4
Microcontrollers / Re: PCB design question (crystal end ATmega)
« Last post by tiger80 on Today at 02:43:21 pm »
Thank you very much for all your suggestions. They are very valuable to me. I took your suggestions into account and drew two more variants: pcb3 and pcb4.
Which one will be the best?
Robert Feranenc on YouTube says that the paths from the crystal to the microcontroller must be as short as possible.
5
I am still targeting 6 or 6.5 digits. I just posted here where this specific ADC and Opamp buffer was in discussion. :) If target would be 5 digit I would just add digital filter on top and would be there. :)
My target is to monitor other references with a mux(MAX4051) and as such low impedance was not absolutely required, but I also want possibly to use it behind that, and as such high impedance is required. I have two temperature NTC rigged to the Arduino which I can log in parallel, and as such with single equipment I would be able to monitor multiple references and temperature variation with a single equipment.
I will test other AZ with this circuit. From the simulations I saw that Ad8628 is spread spectrum and current noise is all over the place, so maybe this is why I see noise. Since other AZ are constant current noise, maybe this will translate in constant offset which I can then get rid with calibration.
If this will not result will focus on the JFET with bootstrapping. Then I will need to change architecture, power supply, maybe negative and positive rail, and new boards. Maybe even LM399 as reference, but then other requirements for power supply. A lot of more work just to monitor a few references in parallel, and more cost as well. :)
My immediate next step when I get back home is: Reduce C20 back to 2nF or something, remove 10nF capacitor between digital and analog ground to make sure it is not bringing noise from laptop to analog side; use other AZ; test speed of PC817 for SPI as I have a bunch around, and maybe can replace isolator with a solution based on it in case noise is traveling through the capacitive isolator
6
General Technical Chat / Re: Aliexpress dodgy GST tax
« Last post by wraper on Today at 02:40:57 pm »
When you sell, you add VAT to the price. Then you deduct the VAT of whatever you had to buy to be able to deliver the product. End result is, you (or more appropriately, your customer) is paying tax for the value increase only. Pretty simple.
VAT is just a sales tax with a lot of back and forth happening in intermediate stages. You as individual just pay tax on full value that sort of compounds in intermediate stages, but actually does not really. Naming it VAT makes no sense for final customer as it's anything but, its name only makes sense in the context of back and forth going in between of businesses and TAX agency. It could be just removed in all intermediate stages (it actually is in cross country sales within EU between VAT registered entities) with the same end result. It's just stupid when I have to pay VAT when clearing customs for shipments for my business to just get it reimbursed by tax agency a month later since I almost never sell within Latvia and to individuals.
But it wouldn't be the same. You buy two things for 1 EUR each, put it together, sell it for 3 EUR, pay after 1 EUR as tax. Your government gets tax after 1 EUR "Value added". Someone else stocks it, puts it in a store sells it for 5 EUR, they pay for 2 EUR value added.  It's the same for the end customer, but it's very different for countries that don't make end product. Besides, what is an end product anyway? A fridge might be an end product for a consumer, or a tool without VAT for a bakery.
Buy two things, get credit on VAT paid for those, then sell with VAT on a full value. It's the same as if you did not pay VAT to your suppliers to begin with.
It's like arguing what's more expensive, $120 thing with $20 rebate or $100 thing with no rebate.
7
Test Equipment / Re: Hacking the DSO2X1X
« Last post by Eula on Today at 02:39:27 pm »
Good morning.

Thank you all very much for the help. Finally the problem was in the USB cable I was testing with. It works fine with my printer, but for some reason, it doesn't work with the DSO.
Using the original Hantek cable I was able to connect correctly.   :phew:

I apologize for any inconvenience this may have caused. :-+

By the way, Aliexpress seller support and Hantek support have contacted me and suggested to try the original cable.   :-/O :-+

Let's say that this is an "X-file"....  :-//

Now what I have to try to solve is the response of channel 2 on square wave signals....

No matter which probe I try, it always shows the same.

Here are some screenshots at 1kHz and 20kHz.


Regards
8
Test Equipment / Uni-T 8803E vs 8803N difference?
« Last post by ms4sman on Today at 02:37:03 pm »
Can anyone help me understand the difference between the 'E' and the 'N' versions of the 8803 bench meter?

I can't seem to find anything online explaining what's the difference.

Thanks!
9
Test Equipment / Re: Most accurate signal generator
« Last post by ebastler on Today at 02:36:32 pm »
Do you know any 10uV signal generator at 1000Hz (what is the highest possible without noise) that won't produce any noise or at least imperceptible?

Before you start buying more equipment, you should read up on fundamental noise contributions and limitations. For starters, there is resistor noise (Johnson noise) which you can't avoid, even with the most expensive source and detector -- unless you go to cryogenic cooling.

The web page below explains some fundamentals and has a handy calculator. You will find that at room temperature, for 10 kHz bandwidth and 1 MOhm input resistance (as found on oscilloscopes), the Johnson noise is already 13 µVrms.  https://www.omnicalculator.com/physics/resistor-noise
10
The Sony VZ-1 is the perfect camera for making videos, much appreciated by Youtubers, it has a decent built-in microphone and 3.5-mm Stereo mini jack and a Multi Interface Shoe for connecting an external microphone.

There is a compatibility list created by Sony, microphones known to work with the camera, and I can confirm
  • Sony ECM-G1 (expensive, ~150 euro)
  • Sony ECM-LV1 (cheap ~ 30 euro)
I tried myself these two, and they fully work!

However ... this beaufutul vlog-camera is known to not work with some third-party microphones. I haven't yet understood whether it's an impedance problem or the mechanics of the connectors or something, the fact is that many complain that, once their external microphone is inserted, the camera no longer records any audio.

"... Sony ZV-1 not picking up audio from external mic ... "
Who? What?  :-//

Sony offers a Microphone Compatibility list.

  • Sony ECM-AW4: Fully Compatible
  • Sony ECM-CG60: Fully Compatible
  • Sony ECM-G1: Fully Compatible <---- I have this
  • Sony ECM-GZ1M: Compatible with restrictions -> ZOOM microphone mode is not available
  • Sony ECM-LV1: Fully Compatible  <---- I have this
  • Sony ECM-S1: Compatible with restrictions -> Set "DIGITAL/ANALOG switch" to "ANALOG", do not receive power supply from the camera
  • Sony ECM-W2BT: Compatible with restrictions -> Set "DIGITAL/ANALOG switch" to "ANALOG", do not receive power supply from the camera
  • Sony ECM-W3: Compatible with restrictions -> Set "DIGITAL/ANALOG switch" to "ANALOG", do not receive power supply from the camera
  • Sony ECM-W3S: Compatible with restrictions -> Set "DIGITAL/ANALOG switch" to "ANALOG". do not receive power supply from the camera
  • Sony ECM-XYST1M: Fully Compatible


The Sony ZV-1 has a built-in microphone, doesn't have any XLR mic/line, but the built-in mic can be disabled when you plug an external mic to the TRS mic/line input.

The Tascam DR-60D MKII is a compact 4-track audio recorder that can be mounted directly to the camera and offers various audio inputs
  • (channel{1,2}) XLR mic/line inputs can provide phantom power (+24V/+48V, power can be enabled/disabled via software)
  • (channel{3,4}) TRS mic/line inputs support +24 dBu input when used as line inputs

I'm thinking of using it because it comes with the XLR lines, which is the professional standard, very expensive > 200 euro, but higher quality!

The DR-60D MKII also offer different outputs to allow the recording of high-resolution audio material in parallel to, but separated from the camera and its video data.

I am thinking about installing the DR-60D MKII under the VZ-1, and via remote control start recording the video and a second copy of the audio on the Tascam.
Obviously, even if the "start" command arrives at the same time, the two devices actually start recording at slightly different times.
A "ciak" signal is needed as the starting point for the rest of the production on { Premiere, FinalCut, ... }

- - - -

What do you think, guys? in this way I would no longer have the limitations on the SONY mic line, and be able to use better XLR microphones  :-//
Pages: [1] 2 3 4 5 6 ... 10 Next