Velocity Detector

For any coilgun project, a velocity detector is essential. Without some method to determine the projectile velocity, there is no way to quantitatively quantify the performance of the gun, and there is no way to fine tune or improve the performance of the gun.



While there are a number of ways to determine the velocity of a low power coil gun without any equipment, when you start developing higher power coilguns, these methods no longer work. There are two main types of velocity detectors which are appropriate for a coil gun project.

Inductive Sensors

A velocity detector which uses two loops to detect the velocity of an object which flies through the loops are actually induction sensors. The main advantage of using an induction velocity detector is that it is very easy to get an object to pass through loops provided that the loops are big enough. The coilgun doesn't need to be accurate or presise, as long as the projectile flies through the loops. Frankly, I wouldn't recomment an inductive velocity detector for a coilgun project mainly because coilguns can be extremely accurate devices, which makes the only advantage of inductive sensors much less appealing.

Optical Velocity Detector

Velocity Detector

The principal of optical velocity detectors is very simple. There are two sets of infrared LEDs and infrared detectors, much like those in television remote controls. You may buy these from Radioshack. The optical velocity detector detects an object passing by the first LED/sensor pair. AT this point in time, a PIC microcontroller begins counting rapidly. For this project and speed of interest range, 7.15 kHz was an appropriate choice. When the projectile passes  by the second LED/sensor pair, the timer is stopped and displayed on the BAR LED. You can read more about my velocity detector here.

LEGAL DISCLAIMER
Coilgun projects can be extremely dangerous if you don't know what your doing. Capacitors can unleash massive amounts of electricity which can seriously injure or kill. Please use this information with caution, as I can not be held responsible for your actions.