http://www.gausspistol.com/Whatcha think?
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More photos--
VideosA Real Electromagnetic Pistol!
* Three coils are precisely pulsed in
sequence to fire a steel projectile
* Two infrared sensors detect the
projectile position within the firing
tube
* Controlled by a PIC microcontroller
* Powered by 8 AA NiCd battery pack
* Built-in battery charger
* Bar display tracks capacitor bank
charge progress
* Battery and Fault LED indicators
* Laser targeting sight
* Makes no sound when fired
How It Works:
The GP-219 Gauss Pistol is a self-contained, two-stage coil gun. What follows is a brief
description of each subsystem and how it all works together to accelerate the projectile.
Subsystems
A. 8 x AA NiCd Rechargeable Battery Pack
Nominal voltage +9.6 VDC
B. DC/DC Converter Unit
Battery charging circuit
Capacitor Bank charging circuit
Regulated +5 VDC output
Regulated +20 VDC output
Laser module supply
Temperature sensor
C. Energy Storage Unit
Capacitor Bank 1, 1,620 uF, 450 VDC
Capacitor Bank 2, 540 uF, 450 VDC
Two parallel-IGBT circuits, one pair to fire each coil
D. Control Unit
PIC microcontroller manages all pistol functions (description below)
Ten-segment LED bar shows cap bank charging progress
"Ready", "Battery", and "Fault" LEDs
E. Sensor Unit
Two infrared reflection sensors detect presence of the projectile
F, G. Coils
Two hardened solenoidal coils, surrounded by iron to enhance flux linkage
H. Preaccelerator
Projectile is held in place magnetically (so it doesn't fall out prior to firing).
Initial velociy (<2 m/s) achieved using a solenoid fired by 10V Ultra Capacitors, which injects
the projectile into the firing tube.
Microcontroller I/O (
PIC16LF819)
Analog Inputs
Temperature level
Battery voltage level
Capacitor bank voltage level
External (battery charging supply) voltage level
Digital Inputs
Projectile detection sensor 1 (interrupt)
Projectile detection sensor 2
Digital Outputs
Fire control 1
Fire control 2
Cap bank charge control
Battery charge control
"Ready" LED indicator
"Battery" LED indicator
"Fault" LED indicator
The Firing Sequence
1. When the trigger is pulled the Preaccelerator injects the steel projectile into the firing tube.
(A non-ferromagnetic projectile will not work).
2. Optical Sensor 1 detects the presence of the projectile at the entrance of Coil 1, and
triggers an interrupt inside the micro.
3. The micro waits for a specified delay time after receiving the interrupt before pulsing the
IGBTs, dumping the charge stored in Capacitor Bank 1 through Coil 1.
4. The resulting magnetic field sucks the projectile into Coil 1. The pulse time is precisely
controlled by the micro to ensure the field collapses fully by the time the projectile is midway
through Coil 1.
The pulse turn-off is the most critical aspect of timing. If any of the magnetic field is still
present after the middle of the projectile passes the midpoint of the coil then the
projectile will experience a "suck-back" effect. Late turn-off could not only slow down the
projectile, it could even cause it to change direction and shoot backwards!
5. The projectile is detected by Optical Sensor 2 when it emerges from Coil 1.
6. The micro waits a specified delay time before pulsing the IGBTs, dumping the charge
stored in Capacitor Bank 2 through Coil 2.
7. The resulting magnetic field accelerates the projectile into Coil 2. The pulse time is
precisely controlled by the micro to avoid the suck-back effect.
All delay and pulse times are calibrated by trial and error to optimize muzzle velocity. These
constants may be reprogrammed for nonstandard coil or projectile specs.
Charging the Capacitor Banks
Charging the Batteries
I will be adding to this page in the near future, including empirical results!
Frequently Asked Questions:
What is a Gauss Pistol?
A Gauss Pistol is a specific kind of "Coil Gun". The term "Gauss" is a unit of magnetic field
strength (the magnetic field of the earth is around 1 Gauss), named for the great German
mathematician
Karl Friedrich Gauss. "Pistol" refers to a gun that can be held and fired with
one hand.
Gauss pistols, gauss rifles and gauss cannons feature prominently in many sci-fi books, video
games and role playing games as stock "weapons of the future".
Then what is a "Coil Gun" ?
From
HVWiki: "Coil Gun: A device that accelerates a ferromagnetic projectile using a coil of
wire and a pulsed power source, usually capacitors. A large current is put through the coil,
making it magnetic and attracting the ferromagnetic projectile. When the projectile passes
through the coil, the current switches off and the coil loses its magnetism, allowing the
projectile to keep going".
Many Coil Guns take advantage of a multistage design, which involves winding a series of
individual coils along the barrel, each of which is fired in sequence adding some (diminishing
amount of) velocity to the projectile. My pistol design has three coil stages.
Isn't that the same as a "rail gun"?
No. A rail gun operates on a different principle than a coil gun, check out this
great explainerfor more details on rail guns.
Why would anyone want to build one?
This project brings a wide variety of engineering disciplines together: assembly programming,
DCDC converter design, thermal management, mechanical design, battery charging, high
current switching, and electromagnetic fields. The gauss pistol project has been a great
challenge and extremely rewarding!
I could use one of these for home security, right!?
This product is for educational purposes only. It is NOT a weapon! You would be better
off buying a nice
slingshot for home defense.
How is a Gauss Pistol better than a regular gunpowder type pistol?
It isn't. Firearms are in no danger of being supplanted by coil guns anytime soon. Coil guns
weigh more, cost more, are far more complex and far less reliable than ordinary firearms. The
limitations of modern batteries are one major obstacle.
So what good are they? There is an inherent speed limit on the muzzle velocity in an
expanding gas powered gun (such as a firearm, cannon). This is due to the high
temperatures and pressures created in the explosion, which effectively places a speed limit of
around 2km/s for this type of system (earth's escape velocity is >11 km/s, for reference).
It is theoretically possible to achieve much higher velocities than that with a coil gun, (maybe
one day approaching a significant fraction of the speed of light!) since there is no explosion
involved. NASA is working on putting
payloads into space using big coil guns.
What education do you need to be able to design something like this?
I have a BS in Electrical Engineering and a BS in Computer Engineering. Nothing has pleased
me more than all the responses from younger visitors who say this project has sparked an
interest in electronics!
Would it improve your gun if you used supercunducting [sic] transporters and 1000V
fuel cells to get more voltage through the ciols [sic]?
Huh?
Why aren't you using Lithium-ion batteries?
Now that's a good question. Lithium-ions have much better energy density than either NiCd
(at least double) or NiMH (a bit less than double). The unfortunate downside is the Peak Load
Current is about one-tenth what a NiCd can safely supply. This is insufficient for the capacitor
bank charging rate I wanted.
Lithium-polymer batteries are available that have high energy density AND high peak load
current, but that would put me way over my battery budget for this project.
Is your Gauss Pistol dangerous?
Yes, in fact the GP-219 is potentially dangerous in many ways:
* Fully charged, the capacitor terminals have 450V across them. If you poke your finger
around in there you could really get a nasty shock.
* The pistol weighs almost 3 1/2 lbs, so it would be dangerous if hurled it at someone's
head or face.
* The sight is a Class IIIA laser module, which causes retinal damage if stared into for too
long.
* When disassembled, many of the plastic parts could pose a choking hazard to children
under 4.
* The kinetic energy of the projectile as it leaves the barrel is a little more than a CO2
pellet pistol. Though the energy is similar, the Gauss Pistol projectile weighs around
12.5 times more than a lead pellet and travels about 30% as fast. It could definitely
cause bodily injury. Never point any weapon, whether turned off or unloaded, at anyone.
Only you are responsible for your actions.
Are you dangerous?
Only when cornered. Or spooked.
Don't you think you have ANY ethical responsibility for selling deadly weapons
intended to kill people?
I have a personal interest in getting as many people as possible interested in learning about
electronics and physics, and hopefully influence a few into making it a rewarding hobby or
career.
There are many high-voltage kits available,
tesla coils,
"jacobs ladder" etc, which could be used
in a violent manner against innocent people or pets. Since they do not happen to be
gun-
shaped, no one seems to get worked up about these items.
Can I buy one?
First I have to make sure I'm covered liability-wise. If you think you might be interested then
feel free to
contact me and let me know.
How much will they cost?
The full assembly book w/ CD-ROM disc will be $20 - $25 USD, full kit of all parts with the
book will be < $400 depending on my final costs.
