Power Filter for Video Transmitter and FPV Camera Quadcopter

When powering the FPV video transmitter (VTX) and camera with main battery, noise from ESC and motors might cause jumping lines and interference to your footage. In this post we will discuss how we can filter out noise in our power.

ESC’s and motors draw large amount of current, and the fluctuation of motor speed and current draw introduce noise in your power system.

Solutions to Noisy Power Source

The simplest solution is to use a separate battery only for your FPV equipment, however the downside being the extra weight. Alternatively you can use a power filter (as known as a LC filter) to clean up the “dirty” power. I wrote a post on how I built one before, check my LC filter build log out.

Here is the schematics I follow to build my own LC power filter.

power filter schematics

For the inductor, make sure it can support the current in the application. Exceeding the rated current would cuase the inductance to drop due to saturation. Lower inductance will affect the filtering effectiveness.

For the capacitor, make sure it’s rated above the voltage of the application. 25V is a good value for 3S and 4S LiPo batteries.

LC-power-filter-components

lc-power-filter

For RC hobby purposes, I don’t think the value of capacitors and inductor matter too much. I have seen people reported good results with 100uH to 500uH inductors, 0.1uF ceramic capacitor (For high frequency noises), and 100uF to 1000uF capacitor with Low ESR. (Important: low ESR caps are extremely important to ensure good filtering)

Why can’t I see this noise from my multimeter?

Noise that affects your FPV gear is normally high frequency voltage spikes DC multimeters are unable to detect them. To Observe them requires much more sophisticated test equipment such as an oscilloscope.

8 thoughts on “Power Filter for Video Transmitter and FPV Camera Quadcopter

  1. kevin

    Oscar,

    What I don’t get in all of this is why filtering isn’t part of the VTX / Camera?
    At a per unit cost of less than a dollar each IMO this would be a trivial thing to add which would greatly enhance the overall performance of a FPV product.

    Reply
    1. Oscar Post author

      We begin to see better power filtering now in VTX such as the Tramp and Unify Pro HV.
      I guess it all comes down to design and cost, extra filtering makes VTX bigger/heavier and more expensive to make.

      Reply
  2. Serkan ÖZKAN

    Thank you for the info. Is there any way to calculate the required capacitor value as a decoupling capacitor in a circuit (eg. a motor driver circuit) that a motor is connected also. Thanks in advance.

    Reply
  3. Deadcow

    The diode is not only for polarity protection. It filters one “half” of the ripple away. You can simulate the behaviour i.e. with LTSpice.

    Reply
  4. Peter Liwyj

    Hi Oscar
    Couldn’t you run the FPV off the balancing plug but off all the cells in parallel? Wouldn’t this eliminate the video noise?

    Reply
    1. Oscar Post author

      you can do that, but the noise is still there, because the power source from balance plug is exactly same as the discharge plug

      Reply

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