Installation instructions

Placement

The filter should be installed close the power input of the sensitive system components, e.g. the video transmitter and camera, and after any switch-mode voltage converter output (speed controller BEC or dedicated BEC).

The installation page shows a few common setups and the recommended locations to put the filter.

Two or more filters can be chained together to add more noise attenuation stages. The filter can be put in front of a servo for filtering twitching and provide power boost during sudden current surges.

Noise sources

Primary noise sources:

  • Speed controllers (FETs driving the motor, in addition to any swich-mode BEC)
  • DC-DC switch-mode power supplies:
    • Step-down (buck) voltage converters
    • Step-up (boost) voltage converters
    • Switched BECs (linear regulators are fine)
  • Digital servos (the conducted noise)
  • Transmitters and cameras (on-board power supply noise getting back on power bus)
  • Electromagnetic induction (generated by electric current passing through wires)

Some cameras are known to emit quite a bit of noise (e.g. KX-171 G2, VSN500 (SN777), VSN505 (KX550), Petite) back onto the power leads. It's recommended to separate the camera power input from the video transmitter input. Try to only filter the power input close to the transmitter or use to a video transmitter with a dedicated camera voltage output to shield the camera noise from feeding back. If interference persists a last try would be to put a filter on front of both the transmitter (reduce input noise) and camera (reduce noise passing back on power bus). Note that the radiated camera noise will still be an issue.

Load

The maximum current allowed to flow across the filter is 1A (1000mA). Do not connect this filter between the main battery and speed controller, the massive current flow for the motor would render the filter unusable.

Ground

Ground-loops should be kept to a minimum and ideally only a single ground wire between any two sides of the system, e.g. if a dedicated BEC is used for powering the R/C receiver, only the speed controller control-signal (throttle) should be connecting the receiver and speed controller (common-ground through BEC).

The common-ground plane should look like a star- or tree-formation, no two points at the extremities connect together. The output should also not be looped back to any point where they originate, this spoils the purpose of the filter. This could cause oscillation and make the wires act as antennas emitting and picking up interference.

Wires

Avoid long power leads on the output of the filter. Consider using two separate filters, if, for instance the camera and video transmitter are mounted far apart. Long wire will pick up electromagnetic interference (if not twisted) and have some parasitic capacitance between them causing oscillation.

Lines carrying power may be a source of interference (EMI/RFI) as electric charges moving through a conductor will produce a electromagnetic field. Some options to minimize the exposure to interference:

  • Twist the wires in a cable to cancel out the electromagnetic fields running along in opposite directions
  • Tap power for ESC, BEC, VTx close to the battery, right at the main leads or balance plug
  • Keep all power carrying lines separated as much as possible, ideally in a star-like formation with the battery in the center

Running power to the video transmitter and camera alongside the speed controller- and motor-power lines is a potential source of interference as mentioned above. Try to cross signal and power lines perpendicular (90 degree) to other power lines and keep video, motor, servo cables separated by 3-5 cm.

System layout

A modular layout of the system would reduce the chance of interference and make the system easier to troubleshoot. If there are any excessively long wires in the system, consider cutting and shortening them or replacing them with shorter versions. Use zip-ties to bundle any slack.

If separation is not feasible or have the desirable effect, the next step would be to introduce filters close to the crucial points in the system.

Typical basic setups and current ratings:

  • Lawmate 2.4GHz 500mW 5V 300mA VTx + BEV/DCP/RMRC-480 12V 100mA camera - Total 400mA
  • ImmersionRC/Airwave 5.8GHz 100mW 12V 128mA VTx + FatShark RCV922 5V 185mA camera - Total 213mA
  • Fox 1.2GHz 200mW 12V 250mA VTx + KX131 5V 180mA camera - Total 430mA
  • Fatshark 2.4GHz 100mW 12V 250mA VTx + Fatshark CCD Killer 5V 60mA camera - Total 310mA