Does capacitor placement matter?
ฝัง
- เผยแพร่เมื่อ 7 ก.ย. 2024
- Does capacitor placement matter on FPV builds and if so how much?
I spent some time running a few tests. Still so much to be done to fully understand it but hopefully this video can help point you in the right direction. If you know more and don't feel like typing it out feel free to get in touch over on Instagram @rcdronecrasher
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I absolutely love the visual nature of this test. helps me understand what's going on much better.
Crazy to think of how much back EMF is coming through the system with 8x massive Motors and tons of weight... especially when all of those motors stop on a dime.
you went into a lot of detail in this video. hopefully it picks up some views because its really helpfull information
Great info!
Great information! Thanks for the testing! I'm curious how much difference a Low ESR cap vs standard makes?
It's a really cool information, thanks a lot
9:00 Was going to say the same - it's an LC filter due to the wire length. Bringing the wires together or twisting them would probably increase the noise quite a bit unfortunately :'( ... I love the testing methodology and old school scope! Right on with sticking the leads directly onto the cap's legs as well. Do the measuring leads run right into a coax to reduce inductance?
Have you considered a TVS diode to take care of higher frequency noise? For a 16.8V battery you'd want a littelfuse SMCJ17CA or SMCJ18CA off Digikey or similar (SMCJ18CA is going to be less reactive but draw a tiny bit less noise off). They're super fast reacting - commonly used for mitigating EMP spikes in MILSPEC equipment in the cold war until recently.
When I cut the wire on the secondary cap down to 7cm the result is just as good. Curious to try twisting them as that's what I always do on builds. Would be a shame if I have to stop doing that 😂. Measuring leads had around 8cm of wire from the clip straight into a standard probe which was then shielded all the way to the scope
And yes I like to run a FetTec spike absorber which is 3 relatively large tvs diodes. Not sure of the spec and I haven't scoped the effect it has but its a logical step against massive spikes
I love that analog scope though :D
Great video
This is all well and good, but what about the whoop format AIO FC boards...and.. what about smaller motors on smaller quads. Moreover, what effect does this have on the actual flight characteristics of the quad. Scope is fine, but what does it really mean. Can you tell the difference "In-Flight".
Definitely. I've had quads that were "unflyable" due to a faulty gyro where correct capacitor placement completely fixed the problem. For whoop boards I like to put the cap as close to the battery pads as possible.
Awesome discussion and testing here! One thing I see a lot when people talk about capacitor placement is that it's the distance from the source that's important. What I'm trying to understand and please correct me if i'm wrong, but wouldn't the critical variable actually be the total resistance from cap to source? Since the time required to charge a capacitor is directly proportional to resistance. So for example you could have a foot long cable running from the cap to ESC, but if you're running 10 gauge wire it'd be equivalent resistance to about one inch of 20 gauge
I did a test with 14cm of 18awg wire and 12cm of 10awg wire. Both were almost exactly the same amplitude of noise (significantly worse then direct mounted). Resistance is a factor but not the main one. More research indicates that it has something to do with the rise time of the spike and how power travels electromagnetically around the wire rather then through it. Veritasium has a video outlining some of how this works. All pretty confusing
This is a great video that I think needs more publicity in the community! I'm curious what conclusions did you come to with length of wire for ESC cap? Less than 4cm?
Wire length of 0cm is preferable😂. If at all possible solder straight onto whatever it is your trying to protect. A couple of cm of wire is alright though. The most important thing that I only just touched on in this video is the value of a small capacitor divectly on the vbat pads of your FC. This makes a bigger difference to gyro performance and power noise then anything else I've tested
@@paulmakesthings I'm actually going to try that and do a comparison of d term noise before and after
@@UnmannedSky some builds are pretty clean without many caps but if your build is noisy now you might be suprised how much it cleans things up. A little 330uf of the right voltage on the FC vbat works wonders
So you would put the cap on the vbat of the FC not the 5V?
@@UnmannedSky yep. Technically both options would have an effect but for a number of reasons filtering at vbat seems to be better
I have hawk pro Mini Magnum 2 / III Parts - BLHeli_32 35A ESC Board it comes with 2 capacitors, don’t know what size they are, but I having a lot of Video Lines in my goggles. One capacitor is lose on the mini magnum board? an I don’t know if that is causing the poor video I get But it’s worse when power is increased when flying? Is there away to check if the Capacitor is Bad an would that cause video lines an noise? I checked VTX an different Antennas,Bands, Channel’s, and VTX Power but No Change in Video image an Lines? Any ideas 🙏
Hello. I'm currently having some issues fitting a suitable cap (50v 1000uf, is that overkill? 6S with Caddx Vista) into my build. I was going to extend it using some spare wire I have, so that I can mount it elsewhere in the quad. Is this a bad idea? Does this completely negate the point of having a cap in the first place?
Sorry for the slow reply. I'd personally rather have a small capacitor mounted close then a big one extended more then a few cm away
little 470uf :) as an EE