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.
More likely rudimentary EMI/RFI suppression.
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 also it only worked at that timeThe 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.
kreyren on 29 March 20, 2024QuoteDiTBho 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)
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.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.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.
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?