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autofocus_termination [2016/03/24 23:27]
vik created
autofocus_termination [2019/04/18 23:34] (current)
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 +====== Proper Termination for ASIs Autofocus Card ======
  
 +The Input Video IN of the Autofocus Card is terminated with a 10KΩ resister, as it expected to share the video signal coming from the camera with other devices like a monitor or video capture card, which usually have 50Ω or 75Ω termination in them. 
 +
 +If the Autofocus card is the sole recipient of the video signal then proper termination has to be provided to avoid noise due to reflections and to maximize the power transfer. ​
 +===== 1) BNC Tee and BNC terminator =====
 + 
 +[{{ af_tn1.png?​direct |Figure 1: BNC Tee and BNC terminator}}]
 +
 +For temporary experimentation a BNC Tee and a BNC 50Ω / 75Ω terminator could be used to see if the systems performance improves. ​
 +
 +===== 2) SMD Components replacement =====
 +
 +If the above BNC tee setup works out, carry out the following modifications of the autofocus board to make the change permanent. ​
 +  * Replace R12 series 75Ω resistor with a short
 +  * Replace R26 10KΩ resistor with 75Ω
 + 
 +[{{ af_tn2.png?​direct |Figure 2: Positions of the SMD resistors on the Autofocus board}}]
 +
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 + 
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 +{{tag>​tech_note autofocus}}
autofocus_termination.txt · Last modified: 2019/04/18 23:34 (external edit)