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This is a 2 stage IR sensor circuit intended to be used as a ballistic speedometer/chronograph for my Coilgun. I based it off a common design for IR proximity sensors. There are 2 output pins to a microcontroller, and +/-pins for 2 IR receivers, 2 IR emitters, and 2 green LEDs to show when the stage is active. When the beam is broken the voltage on the microcontroller output pins will change, allowing me to code proper coil stage firing timing. The potentiometers are for tuning the sensitivity.

5 V NE555 astable timer circuit that blinks an LED at about 1 Hz with current limiting, timing network, control-pin bypass, and supply decoupling.