Capacitors For Noise Filtering in Mini Quad

Capacitors (caps) can make your FPV video signal cleaner, and your mini quad fly better, but what capacitor should you use? In this article we will discuss the types of low ESR capacitor, and explain why low ESR capacitors are important especially for an FPV quadcopter.

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.

Do I need capacitors in my mini quad build?

You don’t have to use caps, but we recommend it. 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.

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.

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.

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.

Low ESR Capacitor Choices

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.

For example this one looks fine from product description: http://amzn.to/2rvJL1a

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 – Edited by Tom BD Bad

36 thoughts on “Capacitors For Noise Filtering in Mini Quad

  1. 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
  2. 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
  3. 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.

  4. 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
  5. 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
  6. 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
  7. 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.

  8. 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
  9. 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
  10. 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
  11. 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
  12. 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
  13. 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
  14. 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
  15. 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
  16. 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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