Hello,
I was looking over the schematics for the source optode in the NinjaNIRS 2021 and saw the circuit that comes after the SMT730D/850D LEDs I was wondering what the signals going to the MOSFET are for is other than to control which LED is turned on. From what I gathered it seems that it is used to control the intensity of the LED. Any help on this would be appreciated.
Yes, correct, these are for selecting the power level.
Pin 3 on connector J1 selects whether the output power is low or high.
E.g. when pin 3 is high and the modulation signal for the 850nm LED (J1 pin 4) is also high, both transistors Q2A and Q2B will turn on, resulting in a large current in the LED. If J1 pin 3 is low and J1 pin 4 is high, only Q2B will turn on, resulting in a much lower current in the LED.
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