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.
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.
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.