Author Topic: EMF pickup from amplifier in I2C line causing glitches. (Now with scope trace!)  (Read 45037 times)

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Offline StarlordTopic starter

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Here https://e2e.ti.com/support/power_management/simple_switcher/w/simple_switcher_wiki/2243.understanding-measuring-and-reducing-output-voltage-ripple is a decent discussion of measuring high frequency stuff in switching power circuits. Note in particular the improvement when using a very short spring clip rather then the hopeless three inch wire with croc clip (The things are ok for strictly audio band measurements, but forget it for anything with RF involved).

I dunno... you're not making a very good argument here.  I mean, sure, the measurements are more accurate, no argument from me there, but does it really make a difference in this application?  If anything, it's merely makes the noise look a bit less severe.  But the peaks are still clearly there.  If i went to all the trouble to do this on my board, maybe I would see half the noise, but what's the point?  It would still be causing glitches.  I guess I could be a little more certain if my filtering would be sufficient to allow me to scrape by, but that's it.

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What is your board stackup, and is it the same as the TI eval board for the power amp? IME such things need to be on at least 4 layer boards to work well because you need a solid ground plane to stand any real chance at all.

It's a two layer.  Another move to reduce costs.  The ground plane is fairly unbroken around the amplifier though, and it's right next to the power input and some big capacitors.  I also isolated the power plane from the rest of the circuit as best I could.  I'm sure this isn't as good as a four layer board, but it is what it is.
 

Online Andy Watson

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I dunno... you're not making a very good argument here.  I mean, sure, the measurements are more accurate, no argument from me there, but does it really make a difference in this application?
What is being said is that without proper grounding you could be chasing problems that do not exist or are insignificant. Here is a thread with some good links to videos about grounding scope probes:
https://www.eevblog.com/forum/beginners/current-measurement-70275/
 

Offline dmills

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Seriously, pick up a cheap SDR and use it to make some frequency domain measurements, cost is only a few hundred quid (You can make reasonably satisfactory near field E and H field probes out of thin coax), and it will at least tell you where the glaring problems are (My bet, radiation from **all** the external cables, power, signal, you name it).
Hell, hire a spectrum analyser and calibrated Yagi, you can do much in an open field site for a day or twos time expenditure and a few hundred in hire costs, of course this might tell you that you have a serious problem, but precompliance work like that is much cheaper then failing at the test house for something you could have caught and fixed.

The FCC only got into the act after the early days of the home computer thing were over (Because they were causing so many problems), so those ribbon cable connected peripherals were ok at the time they were produced, but there was also much less use of the RF spectrum and it was mostly transmitters at far higher power levels then is common today, so the interference was somewhat less of an issue.

It is one thing to do a rush to market job when you know what you are doing, sure you might stuff up, but the basics will be there (Filter the switching converter, input power and output as appropriate), design with reasonable margins, you may get it wrong, but it will probably not be horribly wrong. It is quite another to go there without the understanding to read between the lines of a datasheet (And you always have to read between the lines on a datasheet, they are as much marketing as technical in many cases). 

For example note that the app note for that power amp notes that if external DC power is used the cheapest way to keep radiation from the supply cables down may be to do a proper filter in the speaker output connections, major hint, also the presence of locations for snubber RC networks on the eval board, another not unreasonable hint. I would take the fact that all of the diagrams show an output filter as a sign that while it may be possible to pull off a ferrite bead filter, it is problematic to do well, doubly so if you don't have the tools to test it (Beads saturate, and they seldom give you a curve for current Vs inductance, unlike a proper inductor)....
You do things like filterless (Or bead inductor) when you are doing a run of 50,000 pieces or so and you can amortise the cost of the extra prototypes needed to get it right over the volume, for a run of a couple of hundred the extra prototyping pain will kill any savings.

The 10MHz thing is also not asking for a bead having a self resonance at 10MHz, but for a bead/capacitor network having a combined resonance below 10MHz, not the same thing at all.   

Odds are if you can find a decent experimentally oriented ham radio club, you could get some useful hints there, and those guys understand this stuff (And may well have a spectrum analyser available).

In terms of bringing a product to market compliance testing is small beer, a year of engineering time (nothing much takes significantly less then this when you include everything) has a cost of at least £40K just in pay even if you ignore the hidden costs (at least 80K total is more like it), now add marketing, market research, moulded cases, production set up, all that stuff, and if you get any change out of £150K for a new product intro you are doing very well, £10K or so for the test house? Big deal.

Regards, Dan.
 
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Offline StarlordTopic starter

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Okay, so I'm considering the possibility of foregoing the ferrite bead and putting an LC reconstruction filter or whatever you want to call it on there.  Looks like a low pass filter to me. 

But a 10uH inductor is too large, so I decided to do some calculations and see if I could get away with using a smaller one.

I found this calculator:
http://circuitcalculator.com/lcfilter.htm

So the first thing I did was I plugged in the values TI provided for the components.  10uH and .68uF. 

So, L = .000010H and C = .00000068F.  This gave me F = 61033 Hz and Z = 3.8348 ohms. 

Okay, that seems to pass the sanity check.  61KHz would be in the range of what I might expect for a low pass filter that should leave the audio frequencies untouched. 

So let's see what I can find on Digikey for shielded SMT inductors that are small (0.1" or less) and have high current handling capability:
http://www.digikey.com/short/3482r2

Okay, so looks like I've gotta design around something in the 1uH range.  Let's plug that into our calculator, along with a 10uF cap.  L = 0.000001H, C = 0.00001F.

Hm... F = 50329Hz.  That's fine.  And Z = 0.31623 ohms.  Uh oh.  My gut tells me that Z should be higher if it's to attenuate the noise as much as TI's suggested values.

Well, I can't really use an inductor twice the size.  I wonder if this will be good enough?  Time for another calculator.  I couldn't find one which graphs the frequencies with just LC input, but I found an RLC one.  I'm guessing for R I should input the DC resistance of the inductor.  So I'll do that and see what I get.

Here's the calculator:
http://sim.okawa-denshi.jp/en/RLCtool.php

Let's try this one from Bourns.  Fairly typical values:
http://www.digikey.com/product-detail/en/bourns-inc/SRP2512-1R0M/SRP2512-1R0MCT-ND/4876867

So I input 49m ohms, 1uH, and 10uF into the calculator and...

Fc = 50KHz.  Okay that passes the sanity check.

Well, that's interesting.  The bode diagram shows a relatively flat response up to around 50Khz where there is a peak, then after 60KHz there's a linear drop, and around 1MHz it reaches a 50db reduction.

How much is a 50db reduction?

http://www.satsig.net/lnb/db-calculator.htm

100,000x?  Well damn, that's more than enough I think.  And hell, 10K would probably be sufficient.  I could reach a 40db reduction with a 0.5uH inductor and 10uF cap. 

Thoughts on going this route instead of using the ferrite bead?
 

Offline dmills

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Better, but you are still not, I think doing it quite right, far better to use something like ltspice (Free download, and pretty standard for this sort of thing) and remember to include the speaker as a load resistor.

With 10u you are going to get a lot of peaking at ~35KHz (~10dB) and the impedance seen by the amp falls off a cliff at the top of the audio band which may put the amp into current limit, I would be thinking less then 1u, maybe an order of magnitude less.

(1u + 100n) in each leg into 4 ohms comes out to -23dB @ 1MHz, -65dB @ 10MHz and more or less flat below 400k, your switcher is running at 1MHz, so there is no real need to put the filter too close to the audio band, especially if it puts a deep low impedance point where it can be expected to trip the power amp overcurrent protection.

Filters have two ends and you need to remember to keep an eye on the admittance at the input side or you can get into trouble, you essentially have to design the filter for a specific load impedance which means that you cannot just trade L for C (Keeping the corner frequency constant) without changing Q.

Regards, Dan.
 

Offline StarlordTopic starter

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Better, but you are still not, I think doing it quite right, far better to use something like ltspice (Free download, and pretty standard for this sort of thing) and remember to include the speaker as a load resistor.

With 10u you are going to get a lot of peaking at ~35KHz (~10dB) and the impedance seen by the amp falls off a cliff at the top of the audio band which may put the amp into current limit, I would be thinking less then 1u, maybe an order of magnitude less.

(1u + 100n) in each leg into 4 ohms comes out to -23dB @ 1MHz, -65dB @ 10MHz and more or less flat below 400k, your switcher is running at 1MHz, so there is no real need to put the filter too close to the audio band, especially if it puts a deep low impedance point where it can be expected to trip the power amp overcurrent protection.

Filters have two ends and you need to remember to keep an eye on the admittance at the input side or you can get into trouble, you essentially have to design the filter for a specific load impedance which means that you cannot just trade L for C (Keeping the corner frequency constant) without changing Q.

Regards, Dan.

1u + 100n?  You mean, two capacitors to ground, plus a 1uH inductor in series?  Why two, so close in value?

Also, it's a 2 ohm load, sometimes.  Two 4 ohm speakers, in parallel, configured as a mono bridge tied load. 

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and more or less flat below 400k, your switcher is running at 1MHz

I know I've been talking about filtering a 1MHz signal, but I'm not even sure where that 1MHz signal is coming from.  From what I can tell in the datasheet, the amp should be switching at 400KHz.
« Last Edit: July 05, 2016, 03:30:40 pm by Starlord »
 

Offline dmills

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Ok, so re do the sim for a two ohm load, and fiddle to taste, no biggie.

What I meant was a 1uH inductor in series with each (Tied) output from the amp and a 100nF cap to ground from the speaker end of each inductor, very routine for class D (two inductors and caps per combined output channel).

Now you are going for 2 ohms, so maybe a little more cap would not hurt, possibly 220n instead of 100n, whatever, basically you have fixed L & R, so you need to set C to avoid excessive current draw or excessive peaking (tends to be the same thing), and take the corner being what it is.

IIRC that chip will go at up to 1.2Mhz, and you might be seeing spikes from both outputs, check the datasheet for the output timing diagrams.

Regards, Dan.
 

Offline StarlordTopic starter

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Ive never used LTSpice before, but I installed it and it looked old and shitty, so I tried setting up a circuit in Digikey's PartSim which I had working in five minutes and graphed the output, but I'm not sure the output I'm seeing is accurate and their parts don't provide many parameters to adjust, so I guess both tools have their serious flaws.  I went back to LTSpice and am now trying to set up a simulation, hoping it actually has a graph and noise function like Partsim so I can see a graph of the falloff, but god this software sucks.   I mean they got nothing at all right about the interface.  Mouse zoom is reversed, and if you point somewhere and zoom in it doesn't zoom into that point, it also works in a mirrored fashion from how it works in Eagle and every other cad package out there.  And when I move a component, the wires become detached, or maybe they were never attached in the first place.  It's a mystery!  How exciting. :(  Oh, and how could I forget that you have to cut to delete, you can't just point and press delete, and for some reason to rotate you have to press CTRL-R instead of just R or simply right clicking while you're dragging the object.  Ugh.  Annnd, I can't find any noise function on the voltage source.  I'm betting this software has no ability to graph the output either.

Tell me again why people recommend this tool so much?  There's gotta be something more modern out there.  This looks like a Windows 3.1 application.  I have literally used simulators written in Javascript that function better than this.  And that even showed the flow of electrons in the circuit in real time.

[edit]

Okay I found a noise function on the simulation menu.  I have no idea where it's planning to inject this noise into the circuit.  And I don't see any probe function so I can actually pick the point in the circuit I want to measure.  But it's giving me an error about an unknown parameter V so it doesn't matter anyway. :/  My earlier question about why anyone uses this piece of crap still stands.

« Last Edit: July 06, 2016, 12:24:33 am by Starlord »
 

Online Monkeh

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Tell me again why people recommend this tool so much?

Because it's free and it works. You want better, break out the wallet.

It's really not that hard to work with, you just have to learn not to assume everything works the same way.

Okay I found a noise function on the simulation menu.  I have no idea where it's planning to inject this noise into the circuit.  And I don't see any probe function so I can actually pick the point in the circuit I want to measure.  But it's giving me an error about an unknown parameter V so it doesn't matter anyway. :/  My earlier question about why anyone uses this piece of crap still stands.

If you were to spend your rant time reading the documentation, you might get further..
« Last Edit: July 06, 2016, 12:36:27 am by Monkeh »
 

Offline StarlordTopic starter

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Because it's free and it works. You want better, break out the wallet.

Well PartSim is free, and I'd say it's better.  I may simply have not delved deep enough into it.  I recall now that it has actual part numbers you can select to create a BOM of parts to source from Digikey.  That's where they're making their money.  So even though the base inductor type doesn't seem to let you set its DC resistance it does have the ability to set a spice model, and I'll bet if I choose a real part it will work out better. 

Also a quick google search turns up a number of free options.  Multisim for example looks much more advanced and there's a free edition:
http://www.ni.com/multisim/

I suspect people just recommend LTSpice because it was the first and it's what they're used to and learned in school, because I refuse to believe it's the best of the available free options in this era of open source software.
 

Online Monkeh

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Well PartSim is free, and I'd say it's better.

Say that when their site is down or they decide to take it away and you lose all your simulation data, and all your experience.

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Also a quick google search turns up a number of free options.  Multisim for example looks much more advanced and there's a free edition:
http://www.ni.com/multisim/

... for 30 days, afaik. It's a trial, not a free edition.

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I suspect people just recommend LTSpice because it was the first and it's what they're used to and learned in school, because I refuse to believe it's the best of the available free options in this era of open source software.

'it was the first'? Not by a long shot, SPICE tools date back over 40 years. You could try Qucs if you like, I promise you it's no more friendly, just different.
« Last Edit: July 06, 2016, 12:45:31 am by Monkeh »
 

Offline T3sl4co1l

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If anything, I'd say the FCC ably performed the job they're charged with.  Though it's not clear how long it took them to crack down.

Well going by the copyright date Someone listed, and the date the Wikipedia article states they took action, then it sounds like they got away with it for 2-3 years, assuming they weren't forced to immediately change their design.

And with unknown outcomes -- discard/recall/fine users/fine mfg/etc.

If nothing else, it shows they had to redesign the product; if they had done it right in the first place, they could've saved that NRE.  (How much did it really cost?  Obviously, not enough for them to tank.  Was it less than the initial sales, with no loss of customers, so it was a net win?  Did it hurt instead? No idea.)

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Well, I have plenty of arguments to make regarding that:

Consider Uber, AirBNB, and Paypal.  And all those handling bitcoin.  All businesses which were/are outright illegal under current codes, or whose legality was in an extreme grey area.  These companies exist and are worth billions because the people running them didn't let a few pesky laws deter them.

Ah, now we're getting somewhere! :)

Gray area, yes.  Illegal, no.  If they sat there, asking lawyers and politicians whether their thing is right or not, they wouldn't have gotten anywhere.  Better to put it out in the market and see how well it does.

And indeed, they did quite well.

But be very mindful of the humongous selection bias: these are four successful companies, out of how many thousands that fail for various reasons?

How about another selection: Silk Road.  Obviously, facilitating the sales of illicit products is suuuper illegal...

Likely a lot of white-to-gray market stuff was sold there, too.  Does that make it wrong?

Well..... yes, as it turns out.


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Now add Segway and all those electric scooter/skateboard/hoverboard companies.  All selling products whose use, under the law as written, are illegal.

Don't believe I'd ever heard the Segway called illegal, since its introduction.  But that was a long time ago, and I didn't follow the news about it.

Here's a current appraisal:
https://www.hg.org/article.asp?id=36294
TLDR it's local only, YMMV.

As for the Hoverboards -- that's under a different rule than present subject.

Or, I'm honestly not really sure if it's a rule or more of a suggestion, but in any case: UL approved products must meet design and inspection standards, and must be tested in a lab (again, for a pretty penny..).
Relevant blurb: http://www.ul.com/hoverboards/

As with other rules, if you don't pass the certification, you're at risk of getting pricked with a nasty action.  Getting sued for bodily and property damages, by just one person, would be a rather bad sight worse than getting dinged $5k by the FCC, or having to recall your products.  So, UL safety is rather a bigger concern.

What you get from being certified, is a guarantee that, if someone comes after you for xyz reason, you simply point to the test results and say "sorry dude, lab said go".  Zero liability.

That's a HUGE deal in the US.  Most business operations can be followed, not so much even by the flow of money, but from the minimization of liability.



Again, manufacturers, importers and sellers are at risk here.  It would be unwise for them to import anything that's uncertified (or counterfeit).

It looks like a Hoverboard lawsuit is brewing, but as these sorts of things happen, it'll probably be a few years (and however many more clients) before it closes.  So until then, the jury's literally still out (well, literally only if it goes to trial).



So... you're saying you'd much rather make a few bucks now, and... somehow dodge or neglect or avoid or abdicate your eventual liability from selling something uncertified..?  Because if that's your business plan, you'd better have an aggressive plan to grow your business significantly by the time those liabilities hit.

It's like getting a loan, except the bill comes randomly, at an unknown interest rate...

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Well, if the US / UK wants to remain a competitive player in a global market, in a world were more and more people, like me are able to design and sell electronics online, people who, like me, can't afford to spend over $14K on testing alone (https://www.quora.com/What-is-the-average-cost-to-get-FCC-and-CE-certification-for-a-very-simple-electronic-gadget), and where competition from China and Hong Kong (and soon India), aren't bound by such pithy things as regulations, and who have their shipping costs subsidized by the government on top of that, then regulations are going to have to change.  If the FCC wants products to be tested, then the government, not the small business owner, should bear the brunt of those costs.  And regulations, which are clearly too strict, because even with all those billions of untested products coming in from China the world has not devolved into chaos, need to be relaxed.

Well,
1. You're a small player. You've never mentioned making billions of things.  Yes! Scale matters!  You're not special, you're a nobody.  If you make a billion of something, your product is in the mind of the whole country, and they will collectively bend to make that popular thing, a sure thing.

2. Importers and retailers are liable for this sort of stuff, all the time.  They usually have enough (capital or credit) to take a few blows.  Sometimes, even if you do everything right, import good stuff, inspect it for all the marks, give it a go yourself; you still end up losing.  You have to absorb that cost, and roll it into your bottom line.  Retail is expensive, and this is part of the reason why.  This is why consumer protection laws exist: to ensure that, okay yeah fine you'll have to pay extra for a variety of reasons, but you're much more likely to get a functioning, safe product.  (EU is far more strict about this, of course.)

3. You mention direct China sellers.  In these cases, the buyer is the importer.  They probably don't realize it, but they are liable for their own safety.  There's not much they can do about the seller, except complain with some nasty e-mails or a bad rating.  Absolutely no teeth.  Indeed, a very large part of why that crap is so cheap, is because it's direct import and buyer-beware -- caveat emptor.

Indeed again: if enough people purchase goods in this way, and enough people wind up injured as a result (defective, unsafe, interfering), the ultimate effect will be even worse: an overall chill on direct-China sales.  In the extreme (perhaps it wouldn't go *this* far..), trade restrictions could be increased.  In short: a few bad apples spoil the bunch.  Tragedy of the commons!

4. Back on topic, the FCC will not raise limits, and should not.  I am an electrical engineer, and I like my airwaves clean and functional.  Just as I want my air clear and breathable, and my water pure and drinkable.  The FCC's primary responsibility is to its licensees.  There are a great many radio operators, licensed to use their segments of spectrum, who expect that spectrum to be available, and whom are given rights to take action (c/o FCC) against any sources of interference.  ...Have you heard of the Tragedy of the Commons?



A possible example, combining both aspects: wireless power.

There's been articles about residential heating, using microwaves.  In reality, it's not nearly as unsafe as it sounds, and it literally heats only the squishy meatbags that need it, so it's maximally efficient!

There's been articles about chargers, using various means (ISM band RF wireless; GHz wireless; even ultrasonic power transfer!).

All of these have the same liabilities -- filling the air with a huge amount of energy, that will cause a wide variety of problems (both for bodily safety, and functionality of standard devices).  No matter how viral these schemes go, they cannot succeed, because you can't beat physics.

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Do you think Adafruit and Sparkfun got big by rigorously testing every device they sold?  Of course not.

Most of what they sell, is an incomplete component, and sold as such.  These are FCC exempt -- given that the final manufacturer / end user still meets Part 15 requirements.

Likewise, dev kits and application boards.  I've seen some truly awful ones.  The LTC3810 application board makes pulses <5ns, >50% overshoot, and there's nothing you can do about it.  The pulse shows up all over the board.  In other words, I had the same experience you did: crap everywhere.

The FAE* was clueless; the best he had to offer was: "eh, toss some ferrite beads on it?"

(*Field Applications Engineer; the guy who comes to your office when you phone up Linear Technologies and ask for some help with a particular product of theirs.)

That particular product ended up in a heavy metal box, and the customer wound up with something like 30% higher unit cost than they wanted.  That reflects poorly on us.  At least it wasn't so bad they couldn't market the complete system; that would've been a disaster for all parties involved.

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And why should they, when their parts are just going to be stuck in people's art projects or whatever with wires going everywhere and no attempt at shielding being made?  Now, legally, they might be in the clear because those items are classified as electronic kits, but speaking from an ethics standpoint, is what they're doing really any different from releasing a finished product that you know is going to emit EMF?  I would say not really.  The end result is the same, whether someone has to solder the battery holder and neopixels onto their blinky shoe thing or not.

Just to be specific -- electronic kits have a specific clause in Part 15.  Whereas components don't need to meet any ratings (because... how could they?), kits, assembled according to instructions, must meet regulations.

It's probably a worse deal for the manufacturer, because it's much harder to ensure the end user builds the product to their spec.  In theory, they should be off the hook if the user doesn't follow spec, but who knows.

In any case, the offending user is the first target (by the FCC).  If it's just some dumb art project (good example ;) ), they can simply turn it off, and probably take it apart and move on to the next cutesy thing to lash together.  (Hopefully being a little more cautious next time?)

For much of those electronic components and Arduinos and kits things, that's about the end of it.  They're not meant to be operated as a finished product, and operational performance is the user's responsibility (again, whether they realize it or not; it would be prudent of the seller to provide reminders of this..).

I don't know Adafruit's full product line, but I would suppose they sell things meant for office use (e.g., computer peripherals?), or stand-alone (soldering station..?), and those should meet regulations.

Tim
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Electronic design, from concept to prototype.
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Offline StarlordTopic starter

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Ok, so re do the sim for a two ohm load, and fiddle to taste, no biggie.

What I meant was a 1uH inductor in series with each (Tied) output from the amp and a 100nF cap to ground from the speaker end of each inductor, very routine for class D (two inductors and caps per combined output channel).

Now you are going for 2 ohms, so maybe a little more cap would not hurt, possibly 220n instead of 100n, whatever, basically you have fixed L & R, so you need to set C to avoid excessive current draw or excessive peaking (tends to be the same thing), and take the corner being what it is.

I've been trying to simulate this in Partsim because I couldn't figure out how to get LTSpice to work, but I'm not getting results that seem to make sense.  Perhaps my model is wrong. 









The graph above is the probe of the wire between L2 and R1.


By the way, I found this application note from TI detailing the design of filters for class D amplifiers.  It confirms what you said about excessive peaking tripping the overcurrent protection on pg 6:
http://www.ti.com/lit/an/sloa119b/sloa119b.pdf

If I'm not mistaken, Wo is the cutoff frequency in radians?  How do I convert from Hz to that?
 

Offline CJay

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'wah wah wah, the law isn't letting me do what I want'

I want lots of money, it's only the law that prevents me wandering into a bank with a shotgun and taking as much as they'll hand over, so that should be fine, I mean, it's not as there aren't successful bank robbers who went on to be very rich right?

Seriously, if you're betting everything on this one product then you *REALLY* need to be sure it's legal to sell and works properly or you're in for a world of pain, arguing and ranting against people who have years of experience in product design, compliance testing etc. doesn't remove the fact that your design is poor (being generous).

Oh, and BTW, http://lmgtfy.com/?q=radians+to+hz
« Last Edit: July 06, 2016, 10:10:16 am by CJay »
 

Offline StarlordTopic starter

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I want lots of money, it's only the law that prevents me wandering into a bank with a shotgun and taking as much as they'll hand over, so that should be fine, I mean, it's not as there aren't successful bank robbers who went on to be very rich right?

Yes, let's pretend the real world is black and white, and that there is no difference between designing an electronic product you expect to sell a hundred of a year that might emit enough EMF to interfere with someone's CB radio occasionally, and bank robbery.  That's one hell of a strawman you've constructed there.  Did you get the right permits for that?

Also, let's pretend that EVERYONE doesn't break the law.  Have you ever exceeded the speed limit?  You're putting people's lives in danger so you can get to work a little faster.  I'd say morally, that's less justifiable than what I'm doing.


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Seriously, if you're betting everything on this one product then you *REALLY* need to be sure it's legal to sell and works properly or you're in for a world of pain, arguing and ranting against people who have years of experience in product design, compliance testing etc. doesn't remove the fact that your design is poor (being generous).

I didn't intend for this project to take over a year.  It was supposed to take 3-4 months.  And I've taken pre-orders from customers who bought the previous version to pay for the R&D on the new version.  So you want to talk about bank robbery?  How do you feel about taking people's money for a product and then delivering nothing?  Because that's what you're suggesting I do.


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Oh, and BTW, http://lmgtfy.com/?q=radians+to+hz

Very funny.  You think I didn't google it before I asked?  That conversion is for frequency to RADIANS PER SECOND.  The datasheet specifies Wo is frequency in RADIANS.  Are these the same thing?  Are meters per second the same thing as meters?  No.  That's why I asked people who know better.  I assume the datasheet omitted the per second part, but I don't know that for certain.  And some references I found talked about the conversion requiring a sample rate, and I had no idea what to use for that.

Also, I have to ask, but did you happen to miss the part where I am here asking questions specifically because I want to design a better product and get rid of these emissions?  What I'm taking issue with is that the idea that I should design nothing because I don't know everything and don't have an unlimited budget to make it absolutely perfect.  I feel like if I invented the microwave oven today, people like you would be giving me shit because it kills WiFi in the vicinity and in order to design something that is affordable for consumers, sacrifices need to be made. 

And speaking of microwaves, you know what's ironic is that WiFi only exists because of the microwave. If the microwave didn't make those frequencies nonviable for commercial use, then the businesses that wanted to design wireless routers wouldn't have had an unregulated frequency spectrum to utilize.  That band would have been auctioned off to the highest bidder.  One could make the argument then that interference drove innovation.  And speaking of innovation, I believe that frequency hopping routers were also invented to get around the issue of potential interference.  One wonders what other advances in signal processing will be made because businesses were forced to work around a too common household appliance?
« Last Edit: July 06, 2016, 11:11:35 am by Starlord »
 

Offline CJay

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*snipped more whinging about how unfair the world is and justification of illegal actions because 'bigger boys did it first'*

Yeah, you go for it, can't wait to hear how the compliance testing goes.

Oh.

You've been pursuing this project and begging tech advice, relying on the charity of others then arguing against them when they've pointed out where you are in the wrong.

I admire your determination to bring this thing to market but there are times when you have to grab your balls and accept you might just be wrong.

You *really* need to understand a *lot* more about what you're inflicting on the world, I doubt very much you will be only interfering with CB radios, there are emergency service, military, civil aviation and many other users of the HF bands that you're merrily polluting, you claim that speeding is less morally acceptable than the risk of blanking communications by those users?






 
« Last Edit: July 06, 2016, 11:41:54 am by CJay »
 
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Offline StarlordTopic starter

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*snipped more whinging about how unfair the world is and justification of illegal actions because 'bigger boys did it first'*

You also snipped the bit where I said you were in no position to judge me because you yourself break the law on a daily basis.
 

Offline StarlordTopic starter

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You *really* need to understand a *lot* more about what you're inflicting on the world, I doubt very much you will be only interfering with CB radios, there are emergency service, military, civil aviation and many other users of the HF bands that you're merrily polluting, you claim that speeding is less morally acceptable than the risk of blanking communications by those users?

Over 32,000 people die on the roads each year.  I challenge you to find a single instance of radio interference resulting in a death in the last 25 years.

Also, do you really think military radio communications can be jammed by a tiny device powered by a 12V battery?
 

Offline dmills

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You should really be plotting the voltage across R1, not that it really changes anything, and yes radians in that datasheet means radians per second.

There other ISM bands besides 2.4G you know, the need for space to use for RF heating predates the microwave oven, 2.4G was used for early domestic wifi because it was the widest ISM band for which cheap RF semiconductor components were realistic at the time (And resonant aerials there were small enough), if 2.4 had not been available then within a few years the 5GHz band would have looked reasonable. Some of us used to do wifi (We called it RTTY and Pactor) down in the HF bands, 13.56MHz ISM could be used, but the aerials become a little annoying down there, and the available baud rate is not wonderfully high.

Incidentally, the door seals on a modern microwave oven are a wonder of **really** clever design (A cavity forms a quarter wave short stub, a half wave back from the edge forming a high impedance at the edge, all made from really cheap bent tin), and the door switch (a safety critical component) is a very clever thing in its own way, low cost and absolutely fail safe.
Cost down is often more of a case of really clever design then blowing off the regs.

Regards, Dan.
 

Offline StarlordTopic starter

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Incidentally, the door seals on a modern microwave oven are a wonder of **really** clever design (A cavity forms a quarter wave short stub, a half wave back from the edge forming a high impedance at the edge, all made from really cheap bent tin), and the door switch (a safety critical component) is a very clever thing in its own way, low cost and absolutely fail safe.

That's cool, and clever it may be, but it's still not perfect. At my sister's place, whenever they use their microwave, the WiFi goes down. It's a pretty new microwave too, and there was no visible damage to the door that might have caused leakage. 
 

Offline CJay

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*snipped more whinging about how unfair the world is and justification of illegal actions because 'bigger boys did it first'*

You also snipped the bit where I said you were in no position to judge me because you yourself break the law on a daily basis.

Explain where I admitted breaking the law?

I accept responsibility for my actions and do not try to argue that they are OK because other people do it too.

Like I said, grow a pair and accept you are in the wrong.

Compliance testing laws are put in place because irresponsible people sell products that have potential to cause significant problems for legitimate users and manufacturers of well designed products.

Has it occurred to you for one second that the emissions from your 'product' won't be limited to just the HF bands?

 
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Offline dmills

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, do you really think military radio communications can be jammed by a tiny device powered by a 12V battery?
Get me close enough to the victim device, and NOT a problem!

GPS for example is trivially easy to jam, mostly because it is so very weak at the receiver, and trashing the military codes will not be that much harder then the civil stuff.
 
I can cite a couple of deaths where radio comms problems were at least contributory, mariners who tend to use the HF bands for ship to shore when out of range of the VHF set (Which is limited to maybe 20 miles or so off shore), and the aircraft emergency frequency on 121.5Mhz has been taken out by a malfunctioning plasma telly before now (Tracked down and confiscated by the authorities, no deaths that time but mostly by good luck).

I have had a ONE TRANSISTOR reset circuit for a small micro cause an EMC fail (The thing had enough base inductance to cause it to take off at VHF, solved with a base stopper), you see the strangest things when you start looking.

Regards, Dan.
 

Offline StarlordTopic starter

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Explain where I admitted breaking the law?

You speed.  Don't lie.  Everyone does.
 

Offline CJay

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You *really* need to understand a *lot* more about what you're inflicting on the world, I doubt very much you will be only interfering with CB radios, there are emergency service, military, civil aviation and many other users of the HF bands that you're merrily polluting, you claim that speeding is less morally acceptable than the risk of blanking communications by those users?

Over 32,000 people die on the roads each year.  I challenge you to find a single instance of radio interference resulting in a death in the last 25 years.

Also, do you really think military radio communications can be jammed by a tiny device powered by a 12V battery?

These do ya to be getting on with?

http://www.nybooks.com/articles/2000/09/21/swissair-111-twa-800-electromagnetic-interference/

http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10701029

As for 'jamming', it's unlikely you'd be able to effectively 'jam' communications but you can most definitely cause significant problems for legitimate users of the band you're merrily spewing interference onto.

Your insistence that it doesn't matter because you will only interfere with CB radios is actually a pretty good point, in the US an FCC certified CB radio is capable of transmitting 4 watts of amplitude modulated carrier, they generally run on 12V (even the line powered solid state units are 12V internally) and consume less than 2 amps.

None of your arguments for why you are entitled to eschew your responsibilities hold water.

Pretty much the same power you have available for your device.
 

Offline CJay

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Explain where I admitted breaking the law?

You speed.  Don't lie.  Everyone does.

Prove it.

I can prove I don't.
 


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