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. We can then calculate the amount of time that it took the projectile to travel the length in between the IR beams, which are 4 inches apart, and find the speed of the projectile. If the object breaks the second beam before the timer causes an interrupt, it will stop the timer and read the 16-Bit value in the registers TMR1H and TMR1L. This timer will keep running until the object breaks the second beam or the timer causes an interrupt (on the 65,536th instruction cycle). When an object breaks the first beam the microcontroller starts a timer (Timer1). The operation of this chronograph is rather simple, there are two IR transmitters and two IR Detectors, each transmitter/detector pair is placed exactly four inches apart. Now that we got all of the requirements and setup out of the way, we can move on and finally get to the exciting stuff. Also, if you want to save $3.39, you can buy 16x2 LCD Displays on eBay for $2.99 including shipping.

Then it would be a couple more bucks for the PVC pipe. With all of these parts, not including the board, it came to $38.11 to purchase all the components for this chronograph with all shipping included except for the PIC18F13K50 bought at Digikey. Many of the parts can be bought at a good price at I will tag the cost of each product in the photos below. Some components couldn't be bought as 1 or were cheaper in higher quantities, that's why you may see some extra parts in the pictures. I have gone and posted print screens of some places where you can buy the components. I have not shown any of the SMD components (except for the PIC) in the photo below. Most of these components I had already had on hand, but I would estimate the cost of this project to be around $30-$40. 1x MMMBT2222A General Purpose Transistor Here is a list of the following electronic components required: If you aren't able to make your own PCB's, one can just use some perfboard and point to point wire everything together. The board itself has some spots that are pitted and doesn't look too neat, but it gets the job done. I use the toner transfer method, but that doesn't produce very nice boards when your laser-jet printer needs a new cartridge. The most trouble I had with this project was making the PCB. Although this chronograph is pretty easy to build, a basic understanding of electronics and soldering skills is essential.

Paintball chronograph