Electronics > Projects, Designs, and Technical Stuff

EMF pickup from amplifier in I2C line causing glitches. (Now with scope trace!)

<< < (25/31) > >>

Starlord:

--- Quote from: janoc on July 14, 2016, 12:29:34 pm ---But who am I to criticize, I am not designing stuff for sale myself.

--- End quote ---

And if you were, you would be a fool to admit it on this forum, between the people who think if you're making any money you should be paying an engineer to answer your questions (I guess they think as professional engineers they know everything and would never need to go to the internet to ask for assistance), and those who will criticize you for not engineering your product to aerospace standards thus making it so expensive no consumer would ever buy it.

engineer_in_shorts:
Never said anything about EMC - don't care.  I was curious about you asking for help on a forum and a number of top posters trying to point your project in a different direction, only for you to ignore them.

And yes i did read the post about your business issues. In fact it is nicely archived here:

http://web.archive.org/web/20141220033446/https://www.eevblog.com/forum/projects/customer-w-unrealistic-expectations-what-would-you-have-charged-for-this-job/?

If you are struggling to put food on the table STOP tinkering with these projects AND GO AND FIND A SALARIED JOB --- IMMEDIATELY. If you have one and it's not enough money/hours then go and find another TODAY.  Trust me, it's for your own health both physically and mentally.

CJay:
Wow.... :palm: :palm: :palm: :palm: :palm: :palm: :palm: :palm: :palm: :palm: :palm:

janoc:
@Starlord, I think you need a serious attitude change to be taken seriously and not as a whiny kid with a large sense of self entitlement.

Nobody is initiating any witchhunts. It is your attitude that is a problem, not that you are making mistakes. Start to take criticism as what it is - an opportunity to learn - rather than a personal attack.

I am a semi-hobbyist myself, sometimes building props and contraptions to use at work, but mostly playing in my own little sandbox for my own education and fun. However, I am also aware of the laws and regulations that govern my hobby. I also don't have an EMC lab on hand or a ton of expensive test equipment - but heck, I do the darnedest to try to limit the possible EMC problems where I can, because I know what sort of issues I can have with that. It is fundamentally in my own interest.

The law doesn't make a difference between a "little guy selling to hobbyists" and a multi-billion company like Apple, neither do the fines you can get if you are careless. Apple probably won't care too much about a few hundreds or thousands EUR/dollars/whatever fine, they would be more concerned about the bad publicity something like that would entail.  However, for me, as a hobbyist, having to pay that out of my own pocket certainly would matter!

Whether or not you are trying to make money is really irrelevant here, the point of it was that if you are trying to sell something, it is going to attract quite a bit more scrutiny than a teen building a wireless bug in their garage for fun. Not to mention that your future clients are likely not expecting to be fined by FCC (or whoever is your regulatory authority) in the future because of using your product. That's a good way to end up getting sued, IMO.

The argument about Lady Ada and Sparkfun is not really relevant neither, because they are selling kits and components, not complete products. These don't have to be EMC tested, it is the responsibility of whoever integrates them into a final product. It doesn't make sense to test a component without the enclosure or other parts of the final system because they all can affect the performance - e.g. a metal grounded case acting as a shield vs. a plastic one which does not. And even then both Sparkfun and Adafruit are actually applying for FCC testing these days, even though they don't really have to.


--- Quote ---Maybe if you care so much about EMC compliance you should have spent all the time you spent arguing with me instead explaining how I could make my circuits more compliant without breaking the bank.  All you've managed to accomplish instead is teaching me that when I am inevitably forced to create a new account and burn the old one, to never EVER mention I plan to make any money or sell anything to anyone.

--- End quote ---

Oh puh-leeze. You have been told and explained many times what you have to do, but you shoot down most of the proposed solutions right away. Or you lack the understanding or means to implement them. And that is somehow the fault of everyone else but you.

And the deal with the new account - you somehow think that if you do that people will miraculously start solving your problems for you, because obviously the only thing standing in the way is them knowing it is @Starlord who is asking these questions?

You are asking people to do free consulting for you, refuse to provide information, shoot down the proposed solutions, think that rules don't apply to you for some reason and show incredible arrogance in general and now think that making a new account will somehow change this? Do you think that everyone is an idiot?


--- Quote ---PS: There's thousands of people on Youtube posting their non-EMC compliant electronics projects.  Lots of people designing guitar pedals and amps without any real knowledge of electronics at all, and selling them.  Why don't you head on over there and tell them all what terrible people they are for trying to learn and start a business at the same time, like me.

--- End quote ---

A guitar pedal with a few opamps or linear power amp is typically not going to spew interference all over the place, unlike your class D power amplifier switching in the megahertz range and connected using long wires. If you don't see or understand the difference between these, I think you really should first educate yourself more before you dig yourself into an even bigger  hole than you are in already.


Starlord:

--- Quote from: janoc on July 14, 2016, 11:21:14 am ---I think he is only going to see this type of EMI. Right now his edges are so slow, that any interference caused by I2C lines is not going to have a ton of high frequency harmonics, with the parasitic wire capacitance acting as a low pass filter. However, the moment he fixes the drivers on the line and gets nice square edges, the amount of high frequency harmonics will shoot up, with the long cable acting as a nice antenna. Even 100-400kHz I2C can produce harmonics in HF/VHF bands. I hope the cable is going to be shielded.

--- End quote ---

I suspected that might be the case, as I'm aware of how if you try to compute a Fourier transform on a square wave you'll find an infinite number of frequencies would be required to recreate it perfectly.

Anyway, I'll keep that in mind if I eventually decide to put proper drivers on the I2C lines.

But I would ask why if shielding is so necessary with data transmission over CAT5 cable, why most CAT5 is not shielded?  Does it operate at frequencies that aren't in important bands?  Or does the differential nature of the signal cancel out the noise?  If I used a differential I2C driver chip, would I not need shielded cable?

Navigation

[0] Message Index

[#] Next page

[*] Previous page

There was an error while thanking
Thanking...
Go to full version
Powered by SMFPacks Advanced Attachments Uploader Mod