Caldwell Ballistic Precision Chronograph 1006315-SSI

Product Information

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 (on the 65,536th instruction cycle). 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. 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. After you have drilled the two holes for the IR transmitters, put the drill in the second hole you drilled and make sure it is completely perpendicular to the PVC pipe (there is pictures for most of these steps). Drill through the other side of the PVC pipe. You have just drilled out the hole for the second IR detector. Next, flip the pipe over and measure 4" across the pipe from the exact center of the second IR detectors hole. Make a mark and drill another hole, this one is for the first IR detector. The bullet then passes through the second screen, releasing the short rod, which again triggers the chisel to make a second mark on the long rod.

Custom Carry Case Designed to store and transport Chronograph, Sunshades, Light Kit and Tripod Constructed of Durable Ballistic Fabric Heavy Duty dual zipper design The difference is that since the short rod started a little later than the long one, the mark is made higher up on the long rod. Since we know that the acceleration of gravity is 32 feet per second per second, we can calculate the time the bullet took to travel between the screens. Used with permission from Travis Terry. Then the circuits are changed so that the electricity comes to each magnet through a wire screen. The rods are re-hung on the electromagnets.

Product Details

Now that we have the chronograph up and working, we will find the worst case scenarios and error tolerances of this device. I will calculate the accuracy according to a 300fps velocity (I assume that the IR Transmitters/Detectors are placed exactly 4" apart, I won't account for manufacturing error). As mentioned in the intro, this chronograph also has a Rate of Fire (RoF) mode. This allows the user to determine how many shots per second their paintball marker is capable of. It is pretty straightforward, when switch #2 (S2) is pressed, the chronograph switches from velocity mode to RoF mode and vice versa. The reason I don't drill through both IR transmitter holes and instead I measure 4" from the second IR detector hole is for accuracy. It is to ensure that both IR transmitters and both IR detectors are spaced exactly 4" apart from each other. This minimizes the error in the calculations and allows for greater accuracy. If for some reason parcels are required to be redirected then an additional charge might be levied (where applicable). Also if goods are refused or not called for a charge might also be incurred. This list is not a full and exhaustive list and other reasons may apply.

Caldwell Ballistic Precision Chronograph Premium Kit Contains everything you need to capture reliable velocity data in one convenient kit. Includes Chronograph, IR LED Light Kit, Tripod and Custom Carry Case that conveniently holds all items. The Caldwell Ballistic Precision Chronograph Premium Kit provides accurate velocity measurements across a wide range of shooting conditions. Higher accuracy was achieved by using a high speed 48 MHz processor and by designing a circuit with an advanced data interface that allows each unit to be computer calibrated at the factory after assembly. The end result is the ability to provide much better accuracy than other chronographs on the market (+/- .25%). Although technologically advanced, the unit is designed to be simple to operate, displaying velocity in Feet per second or Meters per second on the large built in LCD screen. The Caldwell Precision Ballistic Chronograph provides accurate velocity measurements across a wide range of shooting conditions. Higher accuracy was achieved by using a high speed 48 MHz processor and by designing a circuit with an advanced data interface that allows each unit to be computer calibrated at the factory after assembly. The end result is the ability to provide much better accuracy than other chronographs on the market (+/- .25%). So assuming that there are no other sources of error (distance is exactly 4", beams are broken identically on each side, etc) we would have an accuracy of 99.865% at 300fps for this chronograph. This is very good, however, there are many other small sources of error that I have not accounted for. Therefore it is highly unlikely that the chronograph that I build or you build will be 99.865% accurate. Nonetheless, it works quite well and I am very pleased with it.We know that the distance between the IR "beams" is exactly 4 inches. So all we need now is to know how long it took the projectile to travel from beam #1 to beam #2. This is what Timer1 is used for. Every instruction cycle (83.3333 ns) the value of TMR1H:TMR1L will increment. The sunshades are extra wide for better reliability on sunny days and are constructed of a durable synthetic material. All in all, I am quite pleased with how the chronograph works. It wasn't very difficult to build and the code itself is pretty easy to follow. Eventually I plan to update the code and use INT0 and INT1 to detect when a projectile is being shot through the chronograph. This will increase the accuracy and allow for much more efficient code. I would like to make a smaller version of this chronograph, but it is pretty tough to make a lot smaller due to the 16x2 LCD Display. Perhaps I will look into using 7-Segment Displays as a means of relaying the data to the user. Patented in 1874, the Le Boulenge ballistic chronograph was the most accurate way to find the speed of bullets until electronics changed everything, but that was well into the 20th century. Here, John explains how this device works.