The obvious question is: how fast is the projectile? To answer this question, he made a timer suitable for counting bullets. The principle is simple. Laser and light sensors will mark the entry and exit of projectiles within a known distance. Facts have proved that there are some problems to be solved.
First, the laser is too narrow and may miss the emitter. The first attempt to correct the problem used a mirror, but the loss was too great – we suspect he used a second mirror. The final answer is to use a series of detectors and remove the collimating lens of the laser to cover a larger area.
This is feasible, so all that remains is a good mechanical design, which can change the height of the sensor and the distance between the sensors. After that, Arduino can take over.
We like mechanical design and the way he manages buttons in 3D print boxes. We can’t help wondering if the first mirror will work better. We also believe that it is best to add some kind of encoder to let the equipment automatically measure the distance between sensors, because it is adjustable. We also believe that the response time and wavelength sensitivity of the photoresist may be a little poor. It seems that photodiodes or transistors will be more accurate and have better sensitivity to lasers and even traditional light sources. But it does seem to work.
How fast is the coil gun? More than 100 meters per second. As a reference, the initial velocity of a. 22 caliber bullet will far exceed 300 meters per second, but 120 to 130 meters per second can still not be ignored.
If you need a coilgun, we’ve always liked the look of it. Or, you may prefer a more futuristic look.