Capacitors For Noise Filtering in Mini Quad

Capacitors can make your FPV video signal cleaner, and your mini quad fly better. In this tutorial we will explain what types of low ESR capacitor you should get and why low ESR is important, and where to install the caps in a racing drone.

Where to buy capacitors?

Here are some reliable sources you can get your low ESR capacitors from:

Solder at XT60

Solder at ESC’s

What is ‘Noise’ and what causes it?

Noise is caused by quickly varying voltages, current and frequencies in an electrical circuit, even a motor running smoothly can cause these fluctuations.

When you think of the changing conditions all the motors on a multirotor experience, you realize that the electrical environment of a mini quad can be described as downright hostile. Your FC, VTX , camera and other peripherals all need stable electrical conditions to run optimally, which places them firmly in enemy airspace, literally surrounded by bogies!

As technology advances allowing for more powerful motors and ESC’s, the problem becomes even more pronounced.

The noise issue is absolutely crucial, it can mean the difference between a fantastic FPV mini quad and something that is completely unflyable.

Why Low ESR Capacitors are Important to Mini Quad?

By adding caps we can help clean up our power a great deal, which gives you the following benefits:

  • Reduced video noise in your FPV feed
  • A reduction in noise that can corrupt motor, ESC and radio signals
  • Improved flight characteristics and performance, by “cleaning up” the noise in the power to the Gyro sensor
  • It might even save your electronics from being damage by voltage spikes caused by Active Braking (Damped Light)

We prefer low ESR capacitors for our purposes. ESR stands for “Equivalent Series Resistance“. Capacitors with lower ESR show better filtering capability as demonstrated in this video.

LC filters are often used in FPV systems to combat video noise as well, but it only protects the system after the noise is induced. Adding capacitor at the source of the power on the other hand, protects the entire system by preventing the noise from being induced in the first place.

Here is an example showing how much improvement it made to my FPV video feed after installing a capacitor at the XT60 power input.

Does my mini quad need capacitors?

You don’t have to use caps, but we recommend it. As mum says:

“Put a cap on, it’s noisy out there!”

If you have a noisy quad (lots of oscillations and hard to tune PID), or noisy video feed, adding capacitors would probably be the first thing to try.

Here is how you can decide whether your quad is too noisy and need cap.

  • Listen to the motors and see if there are oscillation that you can’t tune out with PID
  • Check for hot motors
  • Noise in your video feed is another sign of electrical noise in the power
  • In extreme cases, you can get ESC/motor desync and “death of roll” and cause you to crash to the ground. Noise can corrupt your ESC signals

Even if you don’t have a noisy build, it’s still good practice to add caps. Better safe than sorry right? :) Bent and misshapen props can introduce noise in your power, the adding caps might actually help with that too.

Where to Install Capacitors in a Mini Quad?

First of all, it’s extremely important to understand the polarity of a capacitor, which leg is positive (+) and which is negative (-). If you make a mistake, the capacitor won’t work and can even explode, please work carefully! The shorter leg indicates negative, if you cannot see the negative label on the body.

How to Read Capacitor Spec

How to Read Capacitor Spec

There are 3 places where you can add your capacitors for them to be effective. Be aware that you only need to install caps in one of these locations.

1. On the PDB, where XT60 pigtail is soldered.

Solder capacitor on PDB in mini quad

2.Where the ESC power leads are soldered to the PDB.

3. Or on the power terminals of each ESC (the best choice IMO).

The closer your capacitors are to the source of the noise, the more effective the filtering will be. The ideal place to solder your capacitors is on the pads of the ESC power terminals (option 3). However you’ll need to solder 4 individual capacitors, one for each ESC, small ones such as 330uF should be fine.

If a cap on each ESC takes up too much space, you can solder 1 or 2 larger caps to the PDB (e.g. 1x1000uF or 2x470uF). It might be less effective as the caps are further away from the source of the noise, but I have tried this solution on a few of my quads and it works well enough for me.

Cut the legs of your caps as short as possible for the best results, and to minimize ESR, these tiny leads don’t conduct high current very well.

Thicker wires such as 20awg can be used for extension if there is no space for the cap at the joint, and this doesn’t actually seem to increase ESR by any noticeable margin.

Capacitor Removes Lead and solder wires

Adding Small Capacitor to the Gyro

If your mini quad still has issues with oscillations and hot motors after adding caps to the XT60 and ESC’s power, you might want to consider adding a small capacitor directly to the Gyro’s power supply. This can reduce the excessive amount of noise present in the Gyro’s power more effectively.

This hack is for experienced users only. It’s not easy finding where to solder the capacitor to, and it also requires good soldering skill.

Adding Cap to 3.3V

The Gyro (IMU sensor) on our flight controllers is powered by a 3.3V LDO regulator, so you just need to solder a capacitor to the 3.3V pin of the Gyro, or the 3.3V output of the LDO. The other end of the cap solder to ground.

Popular options are 4V 220uF – 400uF tantalum capacitor: https://amzn.to/2MiaOXi

[Diagram of where the LDO for Gyro is]

The 3V rail should be filtered as close to gyro as possible for the best result.

Very few FC’s share the same 3.3V rail with the MCU and spektrum receivers, so you might be able to access the 3.3V rail on an external solder pad. IMO this is not a good design not having a dedicated low noise regulator just for the gyro sensor, but it does make it easier for you to solder the capacitor to if required.

Adding Cap to 5V

The 3.3V LDO for the Gyro gets power from the 5V rail, so some people chose to filter the 5V rail and claimed to have success cleaning up noise in the gyro. That doesn’t always work but worth a try.

Popular options: 6V 220uF – 400uF tantalum capacitor: https://amzn.to/2O7mEEb

Is it necessary to add caps to the Gyro’s Power?

You don’t have to worry about it if you don’t have issues. If you do, try other easier methods first and treat this tutorial as the last resort.

Anyway, I wish all FC manufacturers in the future can provide proper filtering in the gyro power in their designs. It’s good to know that many latest FC now have capacitors on the Gyro’s power, including Airbot. So hopefully we won’t need to DIY in the future.

Low ESR Capacitor Choices

I linked to some cap options at the beginning of this article.

Here’s a great list of low ESR capacitors from a google spreadsheet, as well as their size and weight so you can pick one that best suits your needs.

25V rated caps should be enough for most builds which use a 4S LiPo, though you may consider some 35V to stay on the safe side, as voltage spikes can on occasion reach higher than 25V. For 5S and 6S builds, you will need even higher voltage rated caps.

Let me know where you get your capacitors from and I will try to add them to this article.

330uF – For Individual ESC

25V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Panasonic FM 10×12.5 0.038
Elna RJF 10×12.5 0.039
Vishay 160 RLA 12.5×25 0.04
Panasonic FM 8×15 0.041
Samwha ML 10×12.5 0.053
Nippon KZE 10×12.5 0.053
Panasonic FR 8×11.5 0.056
United Chemi-Con (UCC) KZH 8×11.5 0.062
Nippon KZH 8×11.5 0.062
Samwha MZ 10×12.5 0.08
Panasonic FC 8×15 0.085
Panasonic FC 10×12.5 0.09
Nichicon PW 10×12.5 0.09
Samwha MK 10×12.5 0.098
Panasonic TP 10×16 0.13
Elna RJ4 10×12.5 0.81

35V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Panasonic FM 10×16 0.026
Elna RJF 10×16 0.028
Panasonic FM 8×20 0.03
Samwha MZ 10×16 0.038
Nippon KZE 10×16 0.038
Vishay 160 RLA 12.5×25 0.04
Panasonic FR 10×12.5 0.043
United Chemi-Con (UCC) KZH 10×12.5 0.045
Nippon KZH 10×12.5 0.045
Panasonic TP 10×20 0.052
Samwha ML 10×12.5 0.053
Panasonic FC 8×20 0.065
Samwha MK 10×16 0.065
Panasonic FC 10×16 0.068
Nichicon PW 10×16 0.068
Elna RJ4 10×12.5 0.7

470uF – For ESC’s or PDB

25V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Panasonic FM 10×16 0.026
Elna RJF 10×16 0.028
Vishay 160 RLA 16×25 0.029
Panasonic FR 8×20 0.03
Samwha MZ 10×16 0.038
Panasonic FR 8×15 0.041
Nippon KZE 8×20 0.041
Panasonic FR 10×12.5 0.043
United Chemi-Con (UCC) KZH 10×12.5 0.045
Nippon KZH 10×12.5 0.045
Samwha ML 10×12.5 0.055
Samwha MK 10×20 0.06
Samwha MK 10×16 0.065
Panasonic TP 8×20 0.067
Panasonic FC 10×16 0.068
Nichicon PW 10×16 0.068
Panasonic TP 10×17 0.13
Elna RJ4 10×12.5 0.57

35V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Panasonic FM 10×20 0.019
Elna RJF 10×20 0.02
Nippon KZE 10×20 0.023
Samwha MZ 10×20 0.027
Panasonic FR 10×20 0.028
Panasonic FR 10×16 0.028
Panasonic FR 8×20 0.03
Nichicon UHW 10×16 0.03
Nippon KZH 10×16 0.032
United Chemi-Con (UCC) KZH 10×16 0.032
Vishay 160 RLA 18×20 0.035
Panasonic TP 12.5×20 0.038
Samwha ML 8×20 0.038
Samwha ML 10×16 0.041
Samwha MK 10×20 0.05
Panasonic FC 10×20 0.052
Nichicon PW 10×20 0.052
Samwha MK 8×20 0.088
Elna RJ4 10×16 0.5

1000uF – For PDB Main Power

25V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Elna RJF 12.5×20 0.017
Panasonic FR 10×25 0.018
United Chemi-Con (UCC) KZH 10×25 0.018
Nippon KZH 10×25 0.018
Panasonic FR 10×20 0.02
Nichicon UHW 10×20 0.02
Nippon KZE 12.5×20 0.021
Samwha MZ 12.5×21 0.025
Vishay 160 RLA 16×31 0.027
Samwha ML 10×20 0.033
Vishay 136 RVI 12.5×25 0.034
Panasonic FC 10×30 0.035
Panasonic FC 12.5×20 0.038
Nichicon PW 12.5×20 0.038
Panasonic FC 16×15 0.043
Samwha MK 10×25 0.045
Samwha MK 10×20 0.05
Elna RJ4 10×20 0.27

35V

Brand Series Size (D X L) Impendance (Ω/100 kHz)
Panasonic FM 12×25 0.015
Elna RJF 12.5×25 0.015
Nichicon UHW 12.5×20 0.017
United Chemi-Con (UCC) KZH 12.5×20 0.017
Nippon KZH 12.5×20 0.017
Panasonic FM 12.5×20 0.018
Nippon KZE 12.5×25 0.018
Samwha MZ 12.5×25 0.022
Vishay 160 RLA 18×35 0.024
Samwha ML 12.5×20 0.026
Panasonic FC 16×20 0.029
Samwha MK 12.5×25 0.029
Panasonic FC 12.5×25 0.03
Nichicon PW 12.5×25 0.03
Samwha MK 12.5×20 0.043
Elna RJ4 12.5×20 0.23
  • Panasonic EB, EE, HD, NHG,GA, M, SU, KA and KS series are not low ESR
  • Samwha SD, BH and RD series are not low ESR, WL and WF are mediocre
  • United Chemi-Con (UCC) with KZM series is comparable to KZH
  • There are much more low ESR Vishay capacitors, but they are just too big
  • Rubycon low ESR capacitors go only up to 220uF – thus not show here
  • Elna RJ3 and RJ4 are comparable

Edit History

  • May 2017 – Article created
  • Oct 2017 – Updated cap options, uploaded a video to show the effectively of adding cap
  • Apr 2018 – Added section “Does my Quad Need Capacitor?”
  • Aug 2018 – Added section “Adding Cap to Gyro’s Power”

56 thoughts on “Capacitors For Noise Filtering in Mini Quad

  1. Justin

    Hi Oscar. Thank you for all the valuable information. Aishi capacitors seem to be quite common in central Europe. Here is a spec sheet. Is Impendance (Ω/100 kHz) on your spreadsheet the same as dissipation factor or tano? capcomp.de/fileadmin/Webdata/partner/AISHI/catalog_seriegroup/ASH_2014_WH_Series.pdf

    Reply
  2. Stephen Shoemaker

    hi, just wondering……..
    I soldered in a cap backwards (polarity). On a new build, on the initial smoke test, it started making a hissing noise and I could see it was getting hot. I immediately disconnected the power and discovered that I had soldered the cap in wrong. I’m guessing the cap is done but am needing to know if there could be further damage to additional electronics. The cap was soldered to a hglrc f428 all in one board where it was designated to be. I replaced the cap with a new one, plugged in again and now have motor#1 get hot very quickly. Any idea whether this could be related??? I’m new to building and not sure where to go from here……any help would be greatly appreciated.
    Sttephen

    Reply
    1. dafunk

      I mounted mine and shorted it. It went in flame and it projected a lot of black smoke in the shape of a cone, relatively easy to clean.
      I have been flying it for 3 months now, all electronics are fine

      I guess you can be lucky and get away with it… just be safe on your first 2 or 3 packs

      Reply
    2. Bj0rn

      Hi Stephen,

      soldering a cap the wrong way only damages the cap. If you hear hissing, you cap is already done for. If it bulges out and smokes, it’s already past that stage. If it explodes into a thousand pieces, well, you get the point.

      Now, the cool thing is, the damage will be limited to your capacitor. By reverse connecting the capacitor, you actually shorted it out. So there was a high current going from the battery through the capacitor back to your battery, heating up the cap and damaging it.

      In extreme cases, you may damage the battery because it discharges at a high C load and if it stays shorted for multiple minutes the battery may discharge down to a voltage that it’s bricked. But since you disconnected it quickly, that kind of damage is very unlikely.

      A motor getting hot is typically related to a worn out motor. I assume yours are brand new since you’re starting in the hobby. You can test using a process of elimination. Swap motor #1 and motor #3 (assuming a quad copter) and see if #1 or #3 gets hot. If now #3 gets hot and #1 doesn’t, it’s probably your ESC. If #1 gets hot again, there’s something wrong with the motor. Electrically, there is not much that can go wrong with a motor. I would expect worn out bearings, a manufacturer error or if it’s electrical in nature, a screw that has protruded part of the windings during assembly. In any case, I expect the cause of hot motor#1 to be not related to the cap.

      Bottom line, your other electronics (flight controller, etc…) will be fine. :-)

      Reply
  3. Moritz Beyer

    Jesus! Lots of comments!
    Well, I hope mine will be new.
    So how does the size of the capacitor matter?
    You recommend 1000 uF at the Power plug. The Bolt32 comes with 2000 uF.
    Should we do 2000 as well? Are there any downsites? What happens with a 500 uF? Just not enough filtering?
    Thank you!

    Reply
    1. Oscar Post author

      The bigger the better if size isn’t an issue for you. I find 1000uF generally can fix most of my issues that’s why I recommend it.

      Reply
  4. Pierre

    Hello Oscar.
    Great article here..
    But i have a question:
    On a 6S build what caps do u recomend??
    And what Voltahe should they be??

    Cheers

    Reply
  5. Simon Ireland

    “Cut the legs of your caps as short as possible for the best results, and to minimize ESR, these tiny leads don’t conduct high current very well.”
    Oscar with all due respect, the filtration Capacitor is not intended to handle high current, nor does it need to. It’s intended to filter out “ripple” voltage spikes within the low frequency spectrum. Adding a few inches of wire will have absolutely negligible impact for the intended purposes. This is particularly beneficial for quads where you need to position the Capacitor away from the FC or battery. It is erroneous to suggest the Capacitor leads must be short.

    Reply
    1. Stephen Gibb

      No its not he is actually referring to the capacitors legs which are in fact quite poor conductors especially at high frequencies.

      The purpose of these caps is to smooth voltage transient spikes not ripple this isn’t a bridge rectifier. The active braking dumps a lot of charge quickly into the system resulting in high voltages if there isn’t enough capacitance to soak it up.
      The instantaneous current can be very high.

      Reply
  6. Roddy

    How about installing the capacitor on XT60 when PDB is equipped with current sensor?
    As far as I know the current sensor has some resistance as well to obtain current by measuring voltage drop. I assume that from FC and FPV supply point of view the sensor’s resistance will add to ESR. So, can this resistance affect filtering performance?

    Reply
    1. maczar

      I think you cannot install capaitor on battery lead when using AIO FC or FC with PDB integrated that is equipped with current sensor.
      In my quad there was no filtering with this kind of connection, same as without any cap.
      When I have soldered caps to ESC power leads ad FC, capacitor are now doing their job – quad is now perfectly tuneable and fly great.

      Reply
  7. Jake

    So far lots of useful info here!
    In case anybody doesn’t already know and is paying hiked up prices for passive components like capacitors on sites like Amazon or Ebay, check Mouser – very fast shipping, industry pricing on a lot of useful stuff. They don’t mess around and you can trust their technical information and specs.
    Just as an example – Amazon pricing on qty of 6 Panasonic FM 330uF 50V caps, $11.68. Mouser has them listed at $0.75 ea., or $4.50/6 (with 100% technical data so you know all the little details and can easily compare!). Of course you have to weigh shipping costs (around $8 where I’m at – Amazon and others typically have free shipping), but if you deal with a lot of quads then you’ll be best served in the long run picking up higher quantities and other useful parts/supplies in one order. You can save a lot of money, and put it back into your quad. ;D

    Curious about one thing here, aside from plugging an electrical parts supplier: Is it a good idea to do an ESC calibration after adding capacitors? I’ve fixed a few issues with unexpected flipping by calibrating, so I’ve been starting to recalibrate ESCs almost every time the quad goes on the bench. I figure it’s easy enough, but wondering if it’s necessary after this little mod?

    Reply
  8. Walkeer

    If low ESR is critical, which I agree, why not use the best capacitors for the task, which are Aluminum polymer capacitors, such as KEMET A750MS567M1EAAE015 or Panasonic 35SEF120M OS-CON SEF Series, which have ERS 0.015 Ohm

    Reply
    1. Simon Ireland

      ESR capacitors are not critical, they are desirable. You can use regular electrolytic capacitors and still get effective filtration. The low ESR capacitors are better but you can’t quantify the difference between the two off this video. It’s just a simple demonstration, not a definitive comparison.

      Reply
    2. Stephen Gibb

      Low ESR whilst still having a sufficient capacitance to do the job poly caps tend to have a low capacitance for there size and weight.

      Reply
  9. Skywalker

    Hi .dear oscar
    I buy rubycon 470 uf 25v zlh series cap . Can i use this cap for my esc s to decrease noises. In google spreadsheet that you say this cap was located. Can i use ?
    Thank you -skywalker

    Reply
  10. Gogi

    Hi!
    Question: i have recently built a quad and i am getting flips of death and i can see via the fpv feed that the fc restarts. Its been made clear that its a power issue. I have increased the idle and all that jazz to no success.
    So my question is would a capacitor fox this?
    ThanX in advance :D

    Reply
  11. Roderick Heal

    Haven’t tried this before on any of my quads but want to try it.

    Which way round should the caps be connected?

    Reply
  12. Jorge

    Hi, I bought a second hand quad with the same red ESC in a picture of the article, and it broke dawn yesterday, I hope yo can tell me which model is, so if yo please can answer this comment as earlier as you see it, I will appreciate.

    PD: Very interesting article.

    Reply
    1. Oscar Post author

      those are really ancient ESC’s (probably more than 3 years old), you are better off getting some latest ESC’s. I don’t even think you can find them anymore from shops.

      Reply
      1. Jorge

        OK, thankyou, I finally found a similar ESC from Eachine of 12A, I wanted to know because, yea is old, but is the best drone to learn racing with Acro mode and nothing happened if it broke
        down.

  13. Fred

    Hello Oscar
    From my experience with tekin esc on rc car, they are using either the rr or rnu series of nichicon capacitor
    Would they be better than your recommended list ?
    330 uf 25v digikey.ca/product-detail/en/nichicon/RNU1E331MDN1PH/493-6635-1-ND/3466049

    Reply
  14. Justyn Markland

    I am using Panasonic fm 270uf 50v caps on my esc’s. I also use the 2 of the same caps on the pdb. This is for a 6s setup. Multiple small caps are better then one large capacitor. The 50v rating gives plenty of head room. 35v would do, but the 50v caps have a lower esr and higher ripple current.

    Reply
  15. Kai

    Is this list of low ESR capacitors comprehensive?

    I found some ‘Sanyo High Frequency Low ESR Radial Electrolytic Capacitors’ for 35V & 50V rated at 470uF & 1000uF (105-deg C) going pretty cheap on eBay. But they’re not on your list.

    Can I use them?

    Reply
    1. Oscar Post author

      It’s likely that it’s missing a few. You can certainly try them although I don’t really trust sellers on ebay for quality products.

      Reply
  16. Ben T

    Hi Oscar,

    Thanks for doing all these videos and sharing the knowledge.

    I put 4 330f Panasonic FM capacitors on my 5″ quad. Emax 2205S, 2300 kv with Aikon 20A ESCs.

    When I plug in, motor 4 will start to spin on its own, even with the quad unarmed. Do I need to re-set the end points or do some sort of recalibration somewhere?

    Ben

    Reply
      1. Buzz

        Usually, a motor that spins up on its own means that you have a malfunctioning MOSFET on that motor’s ESC.

      2. Matt E

        lower your endpoints manually by 10 or 15. should solve the issue. Mine has done this before but its usually seen as motor twitches. if you still have issues make sure you calibrate your ESCs. Google should show many results on the subject.

  17. Cyril MARTINEZ

    Very nice article and explaination.
    As i am willing to build micro quad, i was wondering if the use of capacitors is necessary, du to the increasing weight, and the lack of space inside those frame ?
    What about using capacitors when using 2 in 1 or 4 in 1 ESC’s ?

    Reply
    1. Oscar Post author

      for a micro quad? I don’t think it’s necessary. But it wouldn’t hurt to add one in if there is space.

      Reply
  18. Shamsher

    Will adding the 4 smaller caps to esc’s also clean up the power going to the 5v and 12v bec, or should I use one 1000 micro farad cap on the battery lead? Also will the 4 smaller 25v caps add up their voltage incase the spike is greater than 25v? ( E.g. for a combined 100v protection with the 4 caps)

    Reply
  19. NickB

    Hello Oscar. What about dshot and adding extra capasitors? Are they also needed? I assume that you also have spikes, but people are removing caps from their escs? Or this is irrelevant.

    Reply
    1. Oscar Post author

      People are removing caps to run DShot because it was connected to the signal.
      The Caps we are adding here are connected to the power, so different caps.

      Reply
  20. Scott Cline

    Thanks for this article Oscar. It helps explain a lot of things about adding a capacitor to your build that I would have spent days/weeks/months trying to figure out.

    Reply
  21. Ronald Kotila

    Help I have capacitor Says CKHM 1000uf 25v B105degrees c with number 17 on it and ic circled r will these work on my Quads

    Reply
  22. Ruben

    I read a lot if the size of the caps. Some say 1 470 uf on pdb is enough, other say 1000uf is needed. Does it matter how much caps on the esc itself is placed? Like a total uf on the whole quad?

    Reply
    1. Oscar Post author

      there is no rules on total uf required, it depends on how noisy your quad is.
      But generally speaking 330uF on each ESC, or 1000uF on PDB works for most people. 470uf on ESC would even be better, but a little bigger.

      Reply
  23. Ben

    Gee it would be nice if there were non cylinder shaped Capacitors. Maybe rectangular/cube or circuit board style that could be mounted in line with an esc on the arm of quad.

    Reply
    1. Justyn Markland

      You could make a small pcb board with ceramic capacitors, but you would need a bunch of them. The uF rating is lower on the ceramic caps.

      Reply
    1. Oscar Post author

      LC filter reduce noise getting into your FPV setup… capacitors “clean” noise in your power, so yes, it’s okay.

      Reply
  24. 1337Flite

    No “might” about caps saving your electronics.
    I lost at least 2 x FCs, 1 VTX and an RX for no apparent reason before I found out about spikes, ESC braking and capacitors.
    I now run a single 220uF 25v cap on each ESC and my video is better, but more importantly I have not lost a single component since (except the Tramp I bent in half in a crash – not spike related).

    Reply
  25. Dean Buckner

    What size caps would you recomend when using 2 6s lipos to feed a heavy life six rotor? Not sure what the escs are,,,I would say 40amps

    Reply

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