Troubleshooting Horizontal Stripes on SpeedyBee F405 WING MINI at High Throttle

I. Issue

When using the SpeedyBee F405 WING MINI flight controller (FC), certain video transmitters (VTX) may exhibit horizontal interference lines at high throttle, affecting FPV image quality, especially for VTX or cameras sensitive to voltage changes.

II. Cause Analysis

1. The VTX power supply method of the SpeedyBee F405 WING MINI differs from the SpeedyBee F405 WING APP version. It uses a 5V SERVO BEC or battery direct supply power mode, with the VTX being powered directly by the battery by default.
   
2. As some VTX or cameras are sensitive to voltage fluctuations, high throttle can cause battery load variations that lead to voltage fluctuations, affecting VTX stability and resulting in horizontal interference lines.
3. In testing, we recommend using the SpeedyBee TX ULTRA VTX, which has strong anti-interference capabilities and provides clear images without horizontal lines. However, other VTX models may still be affected by voltage fluctuations.

III. Solution

Method: Parallel Capacitor to Reduce Voltage Fluctuations
The SpeedyBee F405 WING MINI accessory package includes a 35V 470uF electrolytic capacitor. Testing has shown that this capacitor can effectively reduce voltage fluctuations at high throttle, thereby significantly reducing horizontal line interference.

Installation Steps

1. Identify the capacitor polarity and remove the 35V 470uF electrolytic capacitor from its packaging. The longer lead is the positive pole, and the shorter lead is the negative pole, which is usually marked with a "-" symbol.
   ※Note: Do not reverse the capacitor polarity, as this can cause the capacitor to explode!!
   
2. Connect in parallel to the FC PDB board: Connect the capacitor's positive lead to the PDB board's positive terminal, and the negative lead to the negative terminal.
   ※Recommendation: Keep the capacitor leads as short as possible to reduce signal interference and improve filtering effectiveness.
   
   Additional: Battery Optimization

• Aged batteries have higher internal resistance, which can cause significant voltage fluctuations at high throttle and more likely to cause interference.
• Try replacing with high C-value quality lithium batteries to reduce power supply fluctuations.

IV. Verification

After completing the optimization, you can verify whether the interference has been eliminated through the following methods:
1) Power on the flight controller and observe the FPV image

• In a stationary state, check if the VTX image still shows horizontal interference lines.
  2) Increase throttle to test load conditions
• Increase throttle to over 80% and observe if the FPV image still has horizontal line issues.
  

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