The functions of each component in the schematic diagram of the photoelectric sensor speed measuring circuit, please describe in detail. (R8, R9, R10, R12, NPN transistor)

U2---Infrared pair tube

R9---LED current limiting resistor in infrared pair tube

R10--Photosensitive transistor in infrared pair tube The collector resistance

The LED emits infrared light. When the phototransistor receives it, it will be turned on, otherwise it will be turned off. There is a light-shielding film in the part where the speed needs to be measured, which is blocked once per revolution or a specified number of times, so that the speed becomes a pulse signal of a certain frequency.

Q3---transistor

R12--base resistance of Q3

R8---collector resistance of Q3

Q3 plays the role of signal amplification and shaping, making the signal easy to read by the microcontroller.

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