Introduction: Electromagnetic Cannon (coil Gun)

Hello everyone,

In this work I will show you how does electromagnetic cannon work. Main principle of work is that you have some coil and you let current through it, coil generates magnetic field and because of it, the nail, which is in coil, gets launched. You will find out more details in further steps.

I would be grateful if you vote for me, of course, if you like that project. :-)

BE VERY CAREFUL OF HIGH VOLTAGE, CAPACITOR DISCHARGING IS NOT A GAME, YOU CAN GET KILLED!!

Step 1: Introduction

Electromagnetic gun is a device that uses a magnetic field to accelerate the projectile made from the ferromagnetic material. The basic principle is very simple, but in practical execution occurs many problems and complications which together caused small efficiency of cannon. From the initial invested energy only a few percent is converted into kinetic energy of projectile. In basic of thisbeffect is a number of energy conversion. Electrostatic energy of the capacitor is converted into magnetic energy of the coil, and then this energy is converted into kinetic energy projectiles. At each conversion, the energy is lost so the final efficiency can't be high.

About power supply:

We gathered a dozen electrolytic capacitors and connect them in parallel to the battery capacity C = 5.0 mF allowed voltage 400V. According to the capacitor battery we designed the rest of the device. We powered the battery from local powerline (220V) through the regulation transformer and rectifier.

Measuring the speed and energy of projectile:

In order to measure the energy and speed of the projectile, we have created ballistic pendulum. To accurately determine beat of the pendulum we used the camera. The images are processed software and we thus obtain a satisfactory measurement accuracy. All the while special attention should also be paid to safety because we were working with high voltages. Therefore, the entire circuit except coils is housed in a plastic casing.

Step 2: The Theoretical Part:

When the coil length of "l" with the number of turns "N" and current of flowing through the coil generates a magnetic field proportional to the current that flows through it:

B=µ0*µr(N*l/I)

B-magnetic induction (T)
μ0-magnetic permeability of vacuum (4π * 10-7)

μr- relative permeability of core

N-number of turns

I-current (A)

l-length of the coil (m)

Sketch shows the arrangement of forces in the interaction between the electromagnet and soft ferromagnetic material. Because of the magnetic field, the missile begins to behave like a magnet with opposite poles of the coil. The Sketch also shows that the density of forces on the southern end of the electromagnet is greater than on the southern magnetic pole of ferromagnetic (missile), and because of this imbalance occurs attractive force between the coil and missile.

Energy of coil:

While passing a current "I" through the coil inductance L in and around the coils is generated a magnetic field. The energy of the field is calculated by the following formula:

Em=1/2L*I^2

Step 3: Thyristor

Why thyristor, not switches?

The thyristor is a solid-state electronic element which serves to give manageable switches. Includes the excitation pulse to the control electrode, and turns off when the current drops to sufficiently low value that prevents current flow in the opposite direction or fade LRC circuit. In electromagnetic gun is used as a switch to avoid sparks (eg mechanical switches sparks at high currents) and to prevent current in negative direction (current self-induction).

Step 4: The Utility of an Electromagnetic Cannon

The utility is generally calculated as the ratio obtained and invested, so in our case the usefulness gets obtained from the ratio of energy (kinetic Ek) and embedded (electrostatic Eel) energy:

η=Ek/Eel


-The usefulness of an electromagnetic cannon is very small, it is mainly due heat losses of work resistance in the coil which consumes most energy. After time t = τ capacitor breaks out on 37% of the initial voltage. The capacitor is practically breaks out after time t = 5τ.

Et=I^2*R*t

-In order to have effect, the input current must be large, which automatically increases the heat loss. Heat losses could be excluded only by by using of superconducting materials that might have led to cost-utility.

-Large losses occur due to eddy currents.
-Eddy currents occur because of inducing voltage variable field in the conductive loop (coil) and since the projectile is made of iron (conductor of electrical current) then it converts the induced current of energy of magnetic field in warming the missile. (picture above is illustrated projection of eddy currents )

Eddy current losses (Eg) are calculated by the square of the induced current (I) multiplied by the electrical resistance (R) of projectile.

Eg=I^2Rt

Step 5: Block Diagram

Block diagram of the electromagnetic cannon, It consist of several important parts which are shown in picture.

Step 6: Electrical Scheme of the Electromagnetic Cannon

Step 7: Capacitor Battery

In our case, we use a battery of capacitors (in parallel) with capacity amount of C = 5mF and nominal voltage U = 350V. This gives us a reservoir of energy Ec = 306.25 J.

Step 8: Circle for Inclusion the Current Through the Coil

Discharge of the capacitor through the coil was performed by controllable thyristor, and that was done by letting drive pulse voltage for small voltage drop across the resistor (R).

The main reasons why did we use thyristor in junction instead of mechanical switches is to avoid sparks and, most importantly, fade out energy between the coils and capacitors, which would hold back the projectile from leaving the coil.

Step 9:

After a long testing of various coils we rolled out coil that proved most effective. The coil has 11 layers with 40 windings of copper varnish insulated wire, thickness of 1.0 mm. we measure the inductance with U-I method. We have determined the Ohm resistance "R" coil and its impedance "Z" at a frequency of 50 Hz. Substituting into the equation:

L=((Z^2 - R^2)^1/2)/ 2πf

we get value:

L=0,70 mH

Step 10: Projectiles

Measurements are performed with missiles made of two kinds of material. The first measurements were performed with projectiles of reinforcing iron 6 mm thick. We had 5 missiles with masses between 5 and 26g.

Later we used missiles of white ductile iron of thickness 7 mm with a weight range of 11 to 47g. This second type of material proved better because it had a better surface machining, higher density and less friction, so the results were more accurate.

Step 11: Ballistic Pendulum

To measure the speed of the projectile, we used ballistic pendulum due to its simplicity as the effective way to measure the amount of movement and kinetic energy without need measurement of time, but only relies on the mass and shift which is quite easily and accurately measured.

As we can see from the picture, our ballistic pendulum consists of the following parts:

-target(on a wooden mass we stuck styrofoam in order to missile crashed into target, and so gave its momentum to it)

-scale in degrees with dial

-cantilever

-camera for recording deflection of target.

Step 12: MEASUREMENTS

Dependence of energy, speed and efficiency of the initial position of projectile

First, we wanted to determine the dependence of the energy and velocity of projectile about the position of projectile inside the coil, in order to get the greater efficiency of the electromagnetic cannon and that our further measurements were performed in the same conditions.
Discharge voltage we kept constant. Measurements are performed on three different bullets of different weight and length.

From the first picture, we see that the entrance to the coil is marked by zero. Distance "l "shows the position of the missile relative to the input of the coil.

Step 13: Energy of Projectile Depending on Its Position

We see that the projectile have a maximum energy when its tip is right at the entrance to the coil (L = 0cm).

Step 14: Measuring the Speed of Projectile Denepending on Its Position

The above graph shows that the speed of projectile (v / (m / s)) is the largest when the missile lies at entrance of coil (L = 0cm)

Conclusion:

All parameters (energy of projectiles (E / J), velocity of projectiles (v / (m / s)) and usefulness of gun (η /%)) increase as we move closer to the entrance of coil. That's why we have in the following measurements always put a missile on input coil.

Step 15: Dependance of Speed and Energy About Voltage

In second measurement, we wanted to determine how the energy and velocity of projectile and cannon usefulness depends on the voltage discharge. We took projectiles of different length and weight and have kept their same position (top of projectile was at the entrance to the coil, in previous measurements it is proved as the most effective).

In images are tables that we took as examples of usage and speed of projectile.

( tables are copy-pasted from Word, so that's why some words are underlined)

Step 16: Speed of Projectile- Voltage on Capacitor Graph

The highest speed is achieved by projectile mass of 26g. Lighter projectiles at high voltages are braked by rear part of electric impulses that takes too long for them.

Step 17: Voltage of Maximal Speed Depending on Projectile Mass:

We see characteristic projectile mass ratio and the voltage at which the maximum speed is obtained.

Step 18: Energy Dependence on the Voltage Discharge:

We achieve maximum energy with projectile weight of 44g.

Step 19: Determination of Current Pulse

Impulse current and its shape we get using an oscilloscope. Between coil and the switch (thyristor) we connected an extra wire in order not to destroy the oscilloscope due to excessive current and voltage discharge.

At the wire, we measured the voltage drop. The voltage drop on the wire is the same shape as the voltage drop across the coil. (Second picture)

From the curve of voltage drop which creates on a short wire, we can calculate the impulse current, which generates a voltage drop on a short string. Since the wire is connected in series with the coil, through the wire passes the same current pulse as through the coil. Knowing the resistance of the wire and the voltage drop on the wire easily calculate the impulse current:

l=28cm

S=3.8mm^2

________

R=(ρ*l)/S

R=1,32 mΩ

One square on the oscilloscope screen is 0.1 V,and from the image we see that the voltage drop on the wire is 0.25 V.

I=U/R

I=189A

We see that the value of the pulse current goes up to 189 A. However, the current value is very short. One box on the screen oscilloscope is 2ms, which means that the entire discharge cycle is 8ms.

Step 20: Conclusion

For all these measurements, we can conclude that the missile has a maximum speed when there is exactly at the entrance to the coil.

The kinetic energy of projectile and its velocity increases with voltage until they reach the point of saturation. From the measurements we can see that the speed of projectile reach maximum values at certain voltages. A further increase in voltage causes a reduction in speed projectile. This occurs when the electrical impulse takes too long, and one part hampers missile after reaching equilibrium position in the middle of coil. Heavier projectiles have less acceleration, and this is happening to them at higher voltage.

Program in which I was drawing graphs is " LoggerPro", it has a lot of possibilities for doing some measurements or fitting equations with graph, or measuring speed of moving objects on video.

Thank you for your attention, you can also view my other instructables if you liked that one.

Comments

author
judas79 made it! (author)2016-03-04

Great project; I was wondering which kind of Thyristor you are using? I found 2 types of 400v ones even though I do not need that high of voltage; unidirectional and bidirectional. I'm going to order one and learn how it works while I wait for it to get here from China.

author
PRATIKR5 made it! (author)2016-03-01

Can U be more specific about the winding procedure ... lyke no. of layers ... turns in each layer,etc.
Not being able to get it ...
Help .. !!

author
hrx1016 THE INSANE made it! (author)2016-01-24

5 mf is the capacitance of the complete power bank or each capacitor used?

author
ivver made it! (author)ivver2016-01-25

Complete power bank

author
Doc Penguin made it! (author)2015-06-24

How that could just kill a man....

author
ArnoldS7 made it! (author)ArnoldS72015-07-07

It is the Electrical Discharge that could kill you, I do not think he meant the actual projectile. Because Capacitors store electricity until it is full and than discharge all of it at once it makes using capacitors as a general rule dangerous because they can store any where from 9 Volts right up to 24 Volts or even bigger and in practical Electronics and Electric theory along with both scientific and medical communities only a small amount of 1 Ampere (that is a lowly 1.5 Volt) is enough to kill you should it be discharged into your body a particular point in the arithmetic of your heart (meaning if it jolts your body while your heart rhythm is at a certain point) it WILL Kill you by producing/fabricating if you will a heart attack no matter your age or health and only a VERY lucky few ever survived this and we all have pretty bad heart problems afterwards as the electrical particle/particles traveling through your heart and body produces heat which is in a few cases depleted quickly enough so as to not kill you but it still causes calcification of certain veins in my case it caused the calcification/narrowing of a few of my hearts veins luckily no arteries though!

NEVER underestimate the power of Electricity even DC (Direct Current) can and often is fatal!

One more thing to keep in mind is that your own body constantly generates its very own electricity in low voltage (micro volt) count and also have its own unique frequency (Vibration/Sound) as well, all of which gets interrupted when your jolted another problem with AC (alternating Current) which is what buildings run on have a very nasty ability to literary pin you to the ground until the power short circuits or you burn to ash (literary) it is the same deal with believe it or not Static Electricity which is what makes up a Lighting bolt! it is the static vibrations / constant rubbing of dust and water particles trapped through condensation in the clouds that produce static electricity which in turn is trapped by the water particles that is the best electricity/current conduit in the world! even surpassing Gold, that than again builds up like a Capacitor until it can no longer store the electric current and than discharge that current and with about a 1000 drop lets of water statically charged releasing that charge it would be pretty close to 10,000 Volts easily!

a thunder bolt (the most common kind as there are other types of lightning/thunder bolts too!) is said to be any where from 1,000,000 Volts to around 8,000,000 Volts.

Arc Lightning is the type that is most feared with good reason as it can actually travel through the Air particles in the air it self for several miles and than Arc / unload its current into something like a person, and than you hear on the news about this poor guy being strike dead by lightning on a summers day with no clouds in the air at all (or should I say not for miles) it is also one of the three "Super Charged" classified/named lightning bolts that can and do turn trees ; animals and people into ash in a mere split second or so!

I also believe the correct term for the project at least military wise is a Rail Gun (using an Electrically charged magnet to force/"Shoot" or as the Military guys say "Launch" a projectile a certain short distance by the sudden release of the build up charge) most of these Rail Guns and its particular system is used for safely launching Missiles and Rockets as it gives a 1 Meter lay way distance before the Rocket/Missiles engines starts up, I believe the same system is used in certain Rocket Launchers as well and is used in the Hydra that or a lesser known Compressed Gas system that literary through the ignition of a certain gas causing a rapid but relatively safe explosion of heat boost the rocket/missle out of its launch system before the engines takes over makeing it safer to use and increase the travel distance a little bit as well all in one "Package" if you will ;)

author
Doc Penguin made it! (author)Doc Penguin2015-07-08

EXACTLY what i was trying to say....

author
ArnoldS7 made it! (author)ArnoldS72015-07-16

your welcome ;) it is interesting that certain individuals due to what is called the "grid" or the cumulative collection of brain waves (thoughts) are categorized in certain shall we say groups though it is a bad way to classify the manifestation. Thus what makes sense for you may not for another. And than there are those who stand in between and ensure we all come to grasp and understand each other LOL.

if this offends any one than be angry with GOD not me, it is simply a fact from the Neuroscience and Social Engineering Fields. ;P

P.S. EVERYTHING on Earth has their own "Grids" that fit into bigger Echosystem "Grids" that again fit into the "Mega Grid" that is Earth.

author
Jayccob made it! (author)Jayccob2015-11-02

I know this is four months late. but there is a difference between rail-guns and coil-guns.

Rail-guns are the big ones that the military experiments with and they work by passing the charge through the projectile. This creates two magnetic fields that are parallel ( the positive and negative rails) one magnetic field that is perpendicular (which is the projectile). This causes the projectile to be "pushed" down the rails and out. The rails are isolated from each other and only connect when the projectile bridges the gap.

Coil-guns on the other hand have coils ahead of the projectile. The coils create a brief but powerful magnetic field that "drags" the projectile through the barrel at high speed and by the time the projectile reaches the coils the magnetic fields should be collapsed. The projectile continues on under its own momentum.

Another thing to note is the difference in the projectile you need for each one. The coil-gun needs a ferrous one to be pulled by the magnet but the rail-gun needs conductive, but non-magnetic materials like aluminum ( I don't remember what the military uses for this). Also the projectile for the rail-gun needs to be moving before it touches the rails, otherwise it would just weld itself to the rails because of the high current.

I thought you might be interested in hearing the difference and I enjoy your explaintion of the dangers of electrity. It seems like people have a hard time explaining it at times.

author
ivver made it! (author)ivver2015-06-24

Well, actually, not a problem, just like a knife you have in your kitchen :)

author
Machine made it! (author)2014-04-05

I love the magnetic lines diagram. What software did you do that in? I'd like to use the same software for my own electrical experiments.

Robert.

author
ivver made it! (author)ivver2014-04-05

LoggerPro. In that program your can do everything from drawing graphs to measuring the speed of moving object on video. Enjoy and thanks :)

author
napoleonlijun made it! (author)2014-03-29

pretty I do like it

author
ivver made it! (author)ivver2014-03-30

Thanks, that was my intent. :)

author
rubbrdux made it! (author)2014-03-25

Great subject with EXCELLENT experiment technique and reporting!!

author
ivver made it! (author)ivver2014-03-25

Thank you! :-D

author
andreyeurope made it! (author)2014-03-21

Can you post a video with the experiment ?

author
ivver made it! (author)ivver2014-03-21

I was doing this project before few years for science fair project, I didn't have to have video for presentation, so unfortunately I don't have a video.

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Bio: I love doing everything what has some connection with any kind of technology. I love to see how stuff works and how to make it ... More »
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