The project shows you how to build ballistic chronograph based on PIC18F13K50 Microcontroller. The project only been tested with a paintball gun and it is relatively simple to make. It also can record the rate of fire at which a device is firing. The operation of this projectile velocity meter is rather simple, there are two IR transmitters and two IR Detectors, each transmitter/detector pair is placed exactly four inches apart.
When an object breaks the first beam the microcontroller starts a timer (Timer1). This timer will keep running until the object breaks the second beam or the timer causes an interrupt. If the object breaks the second beam before the timer causes an interrupt, MCU will stop the timer and read the 16-Bit value in the registers TMR1H and TMR1L.
PIC18F13K50 then calculate projectile speed by dividing IR beams distance which is 4 inches with the amount of time that projectile took to travel in between the sensors. If the object is too slow, or if the projectile breaks beam 1 but does not break beam 2, the chronograph will display an Error message on the LCD Display.