This specific application relates to small racing quadcopters, which have their own design constraints, but hopefully it's applicable on a larger scale.

Certain brands of BLDC ESCs are very popular with racers because of their small size and high power handling capabilities, which they achieve by simply removing filtering components on the incoming power leads. The most notable example is the LittleBee, which is actually known for blowing out video transmitters with its voltage spikes -- in excess of 50V.

As a physical layout, quadcopters usually have 1 ESC mounted directly on each arm, with all 4 sets of leads terminating on a common power distribution board in the center of the frame. The power leads are generally 16AWG silicone wire, 2-4" long, and carry between 20-30A averaged at 17.4V or less, for 3-6 minutes. The power distribution boards are generally simple 2oz boards with large power and ground planes and exposed pads for the leads to be soldered directly to. Smaller sets of "accessory" pads are broken out as well for components like the video transmitter, but these are directly part of these large pours.

The current idea I have is 20V unidirectional TVS diodes reverse-biased across the 4 sets of solder pads for the ESCs, and a 25v 1000uF low-ESR cap soldered where the battery leads enter the board. The idea is the large, single cap will help to smooth the rise/fall of the spikes, and the TVS diode will clamp anything above 25V before the video transmitter gear "sees" the spike. These spikes happen on the order of hundreds or thousands per second, for the entire 3-6 minute flight. I don't know if this will impact the TVS.

As both space and weight are at a premium in a racing quadcopter, are there any other additional components I can add, change, or modify to help reduce noise being fed from any ESC back into the overall system?


1 Answer 1


Your ideas of adding TVS diodes and caps close to the ESCs is totally correct and exactly what I would have suggested. 1) make sure your TVS diodes can handle the power dissipation of all your spikes, so choose a big package to avoid thermal issues, like 5KP20CA. This is also a bidirectional type, because your system is battery driven, so you do not have a solid potential. 2) In my option the 1000uF cap is not necessary, use two 220uF in parallel instead. Thus you can lower the ESR even more (parallel resistors)

Of course you can add a real L-C-filter before each ESC, but I don't think this is necessary.

Update: There is no need for a bidirectinal TVS diode, just use an unidirectional one. Srry for the confusions. I looked up, which type can be used with 18V Reverse Stand-Off. The results showed that the breakdown voltage is normally at 21.1V and the Clamping Voltage is 29.2V, like for SMC30J18A > Farnell Filter. Thus you should higher the max. voltage of your caps to 30V or 35V.

  • \$\begingroup\$ I don't understand how a battery-powered system doesn't have a solid potential. Can you elaborate? \$\endgroup\$ Jan 26, 2017 at 20:35
  • \$\begingroup\$ It's not solid like e.g. the earth ground in a power outlet. Thus both of your potentials puls and minus move in case of interferences, because both of them are battery driven and do not have an absolute reference. Is this explanation more useful for you? \$\endgroup\$
    – auoa
    Jan 26, 2017 at 20:56
  • \$\begingroup\$ If anything it confirms that I just need a single-ended diode. I'm only concerned about voltage spikes being produced on the positive rail by the ESCs themselves. \$\endgroup\$ Jan 26, 2017 at 20:57
  • \$\begingroup\$ I'm note sure if you got my point, I added a small drawing to show what I mean. \$\endgroup\$
    – auoa
    Jan 26, 2017 at 21:09
  • \$\begingroup\$ I can't see how that would happen though. Nothing pushes below ground, the only way it could do that is to spike hard enough in the reverse direction to overcome the IR of the battery powering it. I'm not concerned about any induced voltages on the wiring from radio sources. \$\endgroup\$ Jan 26, 2017 at 21:19

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