Comment by oakwhiz
10 hours ago
Seems like a missed opportunity to try adding a capacitor dead-bug style onto the board to see if it cleans it up.
10 hours ago
Seems like a missed opportunity to try adding a capacitor dead-bug style onto the board to see if it cleans it up.
If it's really 20MHz++ noise that's screwing him, you need something faster than a through hole capacitor IMO to deal with it.
That being said, I'm not 100% convinced this is a 20MHz++ noise issue.
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.
Look up parasitic inductance.
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.
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?
True.
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.
https://www.digikey.com/en/products/detail/vishay-beyschlag-...
Like this or something similar.
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you can dead bug SMD caps
> If it's really 20MHz++ noise that's screwing him, you need something faster than a through hole capacitor IMO to deal with it.
That's always worked well enough in the past.
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.
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