What is a Capacitor? What is Video Noise? What are Filters?

 How do these affect one another, and how do I clean up my FPV video?

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What is Video Noise?

There can be a lot of noise in a FPV copter build. There are different types of noise. One of the most annoying and hindering would be video noise. This noise, mostly generated by your ESC‘s and Motors is disruptive to your video. This noise is not an actual audio noise, it’s electronic noise, and it is a visual complication. That is why we have LC filters in FPV drones for racing and freestyle. There are tons of options for filters; electronic filters are circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance the ones we want, or both.

There are two types of electronic filters, passive or active, analog or digital. LC filters are a circuit that is very simple, it has a inductor and a capacitor. The inductor is represented by the L and the capacitor is represented by the C. So the inductor resists the differences to the current flowing through, and the capacitor resists changes to the voltage all the way across it. After this noise has been introduced into your quads system, the LC filters try to clean the signal up and filter out the noise. Capacitors are very important because they prevent this noise from being introduced to the system in the first place. Put less noise in, and that’s less noise you have to filter out. The noise you receive from the motors and ESC’s are enough to distort your video, but not high enough to be detected by a multimeter.

Capacitors

Capacitors are a small component that are connected in parallel with the DC power circuits of most electronic devices to smooth current fluctuations for signal or control circuits. In this sport we use low esr capacitors. ESR is the acronym for effective or equivalent series resistance. There is a lot to this, and not to get lost in technical information it’s simplified as a capacitor holds a charge and when the current runs through it charges and discharges according to the needs of the electronic device pulling the current. ESR gets it’s name because it acts like a resistor in series with a capacitor.

Resistors are different so not compared to them, capacitors use a ton of varieties of different codes or abbreviations to describe their characteristics. Physically small capacitors can be difficult to read or make out what is written on them, due to the tight space available for printing, most caps are small. The information here at MyFPVSchool should help you understand and use capacitors.

Choosing a Capacitor

Capacitors are rated with a voltage and a uF, which is the microfarad, and they also have a capacitance value. This what you will use to choose the right cap for you. How many cells in the battery you will be running in your copter, will determine the amount of volts that will run through your quad at any given time. Be sure to never push more voltage through your capacitor than what is designed to run through it.

Sizing your capacitor is a trade off between smoothing and size, you don’t want to go too big, but you want to make sure it can provide enough relief when the voltage spikes. 470uF is one of the most common sizes in the FPV world. Choosing 220uF or 1000uF or even a 2000uF will work, every pilots build and needs are different. Be sure that whichever you select is low ESR as this is very important.

Capacitors, filtering and video noise can get very in depth and we can discuss for hours. This is not our intention, we just wanted to get the basics out for the new pilot wanting to understand a little more.

Safe Flying! & Power Loop The World!

Always remove your props before you work on your copter.

Learn more by reading more My FPV School articles.

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