The capacitor doesn't have a concept of "fast enough", it's a passive component. The signal is what determines what it does when it encounters the capacitor. Non-linearities and capacitor species aside, a good ole x7r 100nF would clean this up.
In general you can just liberally dump 100nF caps all over your pcb power traces and quash most problems like this before even knowing they exist. I joke that you make a circuit then take out your 100nF salt shaker to make it just right.
The capacitor has a self inductance. That's why you use low self inductance capacitors with very short leads or traces in this role. 100 nF ceramics are fine, but you may actually need a 100 nF and a 10 nF side-by-side because of that inductance depending on how dirty your power line is. Fast clocked circuitry can be pretty nasty.
> 100 nF ceramics are fine, but you may actually need a 100 nF and a 10 nF side-by-side because of that inductance depending on how dirty your power line is.
Capacitance value is essentially irrelevant to inductance. The thing that dictates inductance of a decoupling capacitor is essentially only the package size. The way to fix that is to use smaller (physical) sized components. The only reason it may be related is that some larger values of capacitance physically can't fit into tiny package sizes. For 100nF, you have essentially no restrictions though. 0201(i) are easy to find in that value.
That's fair, I was thinking of hole-through components and I should probably stop doing that in 2026... But: if we're being pedantic: it isn't the physical size as much as it is the loop area that the current travels through, and that doesn't depend so much on the size of the package as on how the package is constructed. Low ESR caps such as IDC or LGA type caps will do better than other types even if the physical size is identical. Lead length also still matters, whether physical leads or length of the traces connecting the cap to the device and these should be kept as short as possible.
Through hole parts cap out at maybe low MHz. Many electrolytic caps frankly cannot effectively decouple signals above 100s of kHz even. Above that value, capacitors become inductors due to lead lengths, parasitic resistance, and other details.
To make capacitors work faster, we make them smaller and smaller. Surface Mount Caps are the only way to reach 20MHz++ decoupling speeds, and you need crazier tricks if you need additional decoupling beyond that frequency.
Yes, but we are splitting hairs at that point. The transient spike is a high impedance voltage that is tripping the high impedance internal protection circuitry of the magnetometer. So whether we have 20mOhms of capacitive decoupling or 500mOhms of inductive decoupling, both are better than the infinite impedance of nothing there.
We're not building a precision filter, were cutting the paws off of a paper tiger. No need to let perfect be the enemy of good.
This is a circuit with a switching regulator that is, presumably, stabilized with something on the order of a 10uH inductor + 22uF capacitor.
So from my perspective, increasing the capacitance from 22uF on that output line to 22.1uF with a 100nF cap will likely do jack diddly shit.
It is far more likely that, ex, the author of this post screwed up the regulator design. Ex: did the author mistakenly think that more capacitance is better-er and stick a 100uF cap there, blowing out the phase margin of the feedback of the switching regulator?
Was the inductor properly sized? Not just inductance but also saturation current and internal resistance?
It's an easy test though and it can be an SMD component and some PUR-coated magnet wire or 30 awg single stranded kynar hookup wire.
Use a small amount of glue from a hot glue gun to fixate it when done, or epoxy if that's your thing. Avoid cyanoacrylate. Not always needed but I imagine a drone moves around alot.
Bodge wiring is a good skill to acquire - PCBs will not always be perfect. Maybe practice on something else first?
I have a bunch of through-hole parts for these sorts of situations. There are plenty of small through-hole ceramics that have leads if you really want to go there.
That's because you weren't dealing with 20MHz noise.
Hobbyists are not dealing with 20MHz noise issues. Period. And if you are actually crazy enough to deal with high frequency circuits like that, you would well know that the land of through hole designs is simply insufficient, and that you are probably somewhere with some 0402 capacitors and some tweezers right now.
> Hobbyists are not dealing with 20MHz noise issues.
It happens. Not often, but it does happen and it depends on the hobbyist and what they're up to (but you won't be sticking that together on a breadboard). Also: if you start using HCT, AHC or even G parts where you don't really need them it can happen to you in places where you don't normally expect it. Those things have crazy fast rise times.
Real talk: 6 layer oshpark is cheap enough for a hobbyist and there are a bunch of 500MHz / DDR2 parts that can be laid out. Like 0.8mm pitch BGAs can fit and breakout.
So yeah. Hobbyists can go here. But here be dragons!!
Nonetheless, I continue to assert that typical hobbyists are making mistakes at 100kHz region rather than the 100MHz region.
That's fair. It's just that I have seen some hobbyists doing the most insane stuff and eventually getting it to work. Some HAMs for instance have pretty extreme skills and it is not their profession, they just do it because they like it, not because they get paid.
And in many of those cases their skills are hard capped by their budget for test gear and simulation software rather than by their actual ability. Keep in mind that until not that long ago anything above 1 G was fair game because 'nobody does anything there anyway' and so HAMs and radio astronomers were pretty much the only ones with experience in that region.
MCP6002 jellybean is GBP of 1MHz. Most "jellybean" OpAmps I know cap out at 10MHz GBWP (aka: a useless 10x gain at 1 MHz).
LM358B is 1.2 MHz GBWP or even 700kHz depending on the design. Magnitudes away from 20MHz especially when you want more than 1.0x gain.
If you want even 10x gain (aka around 10% error), you might suffice with 200MHz GBWP at 20MHz. Or maybe get a nice ADC and just go all digital given today's equipment...
Come on man. Typical "high speed" OpAmps are like 100MHz GBWP or less... correlating to only 5x gain at 20MHz. This sort of stuff is well outside "jellybean" amps. And I'm not even sure if a 100MHz amp is very effective at 20MHz.
LT1812 is my weapon of choice for ultra low RF stuff (think Tayloe mixer frontends). Readily available, pennies to buy, reasonably flat to about 20MHz although THD is getting a little rough up there, possibly because I'm using it wrong.
Looks like they're closer to $3+? Like this is more expensive than a lot of microcontrollers for just one OpAmp.
I wouldn't call any Analog Devices / Linear Technologies parts to be a jellybean. Jellybean means matching common specs that any manufacturer can do.
But at $3 per chip, that's very far away from jellybean status. And AD / LT devices are known for high quality that no one else replicates.
> although THD is getting a little rough up there
Yeah, because a 100MHz high speed OpAmps only has 5x gain at 20MHz. So your error is now well in excess of like 20% (best case) or probably way way worse errors in practice.
As I said earlier: Im not even convinced that 100MHz OpAmps have the GBWP to effectively operate on 20MHz signals. You need more GBWP than that to be comfortable.
This is open source. You're thinking of trusted execution, audits, licenses with disclosure requirements, or signed affidavits which is a totally different thing than open source. Otherwise you could claim that just about anything isn't open source just because you're not sure what is happening on someone else's computer.
ok. This is open source of _what_? Without tying the code to a real life object the intent is absolutely meaningless. Here's the open source code for hackernews:
What does that give us? We can't run this to host our own hackernews as it's clearly not runnable. We can't really learn anything from this as it doesn't not represent any real reality. Maybe it's a fun reading exercise but that's about it.
Open source means that I can take source and run it to ensure it's trusted. Ascii characters being visible on my screen is just a nice byproduct of this goal.
Yeah, leaving hanging loops with a gentle bend radius is very common as long as the loop is secured, and does not cause problems. Maybe something pulled on it though?
Bends ideally need pull boxes, but given the lack of pull boxes, you might be able to use fish tape where where fish rods / glow rods don't work, if you cannot get a pullstring / pull cable going.
The failure rate of an individual layer of Swiss cheese should be bounded under most circumstances but not all. So you should probably have more layers when hazards cannot be eliminated.
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