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| The
Barrier of ON time
Because
of the nature of a high power solenoid, LC time constants will
be longer than the travel time of a fast moving projectile.
Longer LC time contants yield slower projective velocities. In a
tuned LC discharge circuit, the LC
time
constant is < or = to the
projectile’s travel time into the coil; ie,
the full
instertion time with equal coil/projectile lengths.
Majority of the source energy should be depreciated before the center
of the projectile reaches the center of the coil. Unfortunately,
in actual circuits that do not fully exhaust the source energy at the
moment of full projectile insertion, excess current works in
opposition to the projectile’s acceleration and from here on is refered
to as negative force. This excess
precludes capacitors from simply being scaled up in parallel for higher
powers. At least during the experimental phase, one can not rely
of this highly sensitive concept of a tuned circuit with
an open loop design to produce the best efficiency.
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The Barrier of
Precise Triggering
Open loop design, using fixed and assumptive on/off times of coil triggering without knowing the actual projectile's position, has been my first approach. Given both are fixed, coil inductance and projectile dimension, a circuit can go out of tune merely by under/over charging the source capacitors from the design voltage by %15. In the case of under charging, the kinetic output is lowered because the initial potential is lowered. In the case of over charging, the kinetic output is lowered even though the initial potential has been raised. This reduction in efficiency is a disappointment. One would think that if you keep adding more and more capacitors, then the projectile will approach ballistic velocities. Unfortunately, what will happen to an unsuspecting victim is that the projectile will reverse directions to either do harm or at the least induce fright. Now, circumvention proudley enters with the solution smoothly forthcoming and only awaits our implentation. Closed loop design, the detecting and relaying back of a projectile position to the control circuitry, allows for better efficiencies by triggering successive coils at the optimal time. Triggering not only means turning on but also includes the turning off of coils if circuit devices allow such a luxary. I have used and abused many IGBT(s). Of them, non were suitble for my project. Well actually, it turns out that I did not correctly protect these very sensitive transistors. Closed/Opened Loop switching Clarification What is the primary purpose of a closed loop design? The question is better posed as “Which is the primary purpose of a closed loop design: verification alone or error correction?” If the choice is error correction, then it must be concluded that the main-stream idea of using optics alone is not correct according to definition of closed loop stated below. Closed Loop: This method consist of two acts, the act of verifying and the act of correction. Correction here is defined as: processing the current projectile velocity, and adjusting the discharge times for the next stages accordingly. The governing distinguishment is “active”. A status is recorded, compared, then corrected if so needed. Opened Loop: As for optics alone, the only distinguishment from a closed loop method is its singular distinguishment of “verification”. Without a controller, whether it be a microcontroller, RC/Crystal timer, or logic counter-timer, optics only possess the ability to verify the existence of a projectile during its traversal through succeessive stages. Contrary to a closed loop, optics will not perform error correction because their timings are hard coded in the form of gaps between coil stages. Hence, any undesired condition which alters the timing away from the optimum velocities of the beginning stages induces a lowered efficiency of the system as a whole. The extent of the deficiency is dependent on the degree of the initial alteration. The same is true for coilguns controlled by temporal switching. Since a temporal switching method operates under the definition of an opened loop and suffers the same effects here, then passive optical switching should be considered as an open loop design as well. |
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| The Barrier of
Charging Cascades,
transformers, boosters, photoflash flybacks are part of the many
methods yet still are the most common of them to accomplish the same
task, charge a capacitor from 0v to any place between and including the
rated working voltage. Not just charge 1 capacitor but many
connected in a collection otherwise called a Bank. More to this,
charge the Bank in a practical amount of time from a practical power
source which occupies a reasonable volume of space. There in lies
the barrier of which I brake down via the chosen implement known as the
Booster.
The Booster is beautiful. Booster is small, light weight, and most importantly the Booster is powerful. The little 3 triad component count, inductor, diode, and switch, serves best in small footprint circuit boards fitted into small coilgun pistols. The star is the switch preferably an IGBT. I place the IGBT on a pedestal for these 2 specific properties, high switching voltage and low current drive operation. Capacitor banks span from 300v to 600v with 800v not being unreasonable. Thankfully, an IGBT's switching voltage span is equal to and greater than common cg needs. These following schematics illustrate the building levels from the foundation to advanced of a boost converter.
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| The Barrier of Power Discharges | ||||||||||
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