Creating a Low-Cost EMP Device: A School Project Idea

[Greywolf]

This is Somewhat Physics and somewhat technology question but I thought I would ask anyways. I am thinking of making a small EMP device for a School project. However I have afew questions, first would have to be, has anyone else seen a project like this done or attempted before? Also I wanted to ask if this can be done in such a way that it wouldn't cost me afew thousand dollars?

Any ideas would be appreaciated

 

[LogicalAtheist]

Advice - Don't stand to close to it, heh. Use a remote with a LONG RANGE, and do it in the desert, and not near me please (I live in GA).

 

[Greywolf]

lol no worries I live in Canada, and if by some chance I do hit you I'll have to go through afew states. However any suggestions on building this? From what the physics teacher told us, we need a coil of wire around a metal preferably IRON, and if we charge a capacitor and send it through the wire in an instant it should create the EMP? Can you add anything to it?

 

[Alexander]

Start with ole good capacitor discharge - like Hertz and Popov did 100 years ago to generate EMP. Take two similar capacitors, attach simple dipole to them and connect one of them to oscilloscope. You will see decaying oscillations every time you discharge another one nearby.

The more energy CV²/2 you pump into capacitor and the faster you discharge it, the larger is the range at which your EMP can be detected. So low-inductance high voltage "door knob" ceramic capacitor banks charged to high voltage will make a good transmitter, especially if you match antenna size to half wavelength (c/2f) of oscillations. Those capacitors and HV power supplies usually can be bought reasonably inexpensive (few tens bucks) from surplus laser equipment companies like Meredith Instrument or such.

Be careful with charged to few KV capacitors - if the energy in them goes beyond 10 Joules it is painful shock, and if stored energy is beyond 200-300 J it can kill.

If fat HV capacitor or power supply is beyond you budget, you still can experiment with small Radio Shack capacitors charged by 9v battery.

If you want to use a coil antenna, keep it short and don't use iron or anything - it makes decay slow and essentially damps your energy into losses in bulk metal.

 

[MrCaN]

Your best bet is to do a search for HERF devices, they are similar to what you are talking about, most emp weapons are pulse weapons, so keep it away from electronics, but a HERF gun is directional.

Another, mabey more dangoures, but easier to construct is a rail gun, those can be fun and use a lot of electricity too.

 

[Greywolf]

yea a lot of people say a rail gun would be a better idea, but i have NO CLUE how to make those. The emp device I atleast have an idea

 

[MrCaN]

a rail gun is pretty simple, you creat two conducting rods that run parrallel to each other, then lay another one across them, and run a huge voltage through the two rails to shot the third rod, or disk or whatever.

 

[Ivan Seeking]

Dangerous Stuff...but fun.

I have played around with this stuff a bit over the years. Here are a few considerations.

1) Explosions are likely. Act accordingly. If you don’t know what you’re doing, and even if you do, this can be really dangerous stuff. BE CAREFUL!

2) If you use capacitors, look closely at the ESR - Effective Series Resistance - of the capacitors used. This is usually the biggest limitation for cap discharge. Some capacitors are designed to discharge quickly [very very quickly] and others are not. Some capacitors can explode if discharged too quickly.

3) Making a fast and safe switch [to control the large current flow] can be a little tricky. Most switches are used only once. I have had pretty good luck using a high voltage, low current discharge to create an ionized path for the high current discharge to follow. This ionized path is the switch. This way you can control a small current, which in turn enables the flow of a large current. Another successful method used for switching was to fix two parallel plates near each other and then drive them together with a really big sledge hammer. However, as the size of the capacitor banks increases this method looses its appeal.

4). Single pole generators are an interesting means of producing large pulses.

5). If you attempt inductive energy storage watch out for the mechanical forces produced. In fact, this is true for any conductor. Large currents can make a motor armature out of your entire set-up. Then things short out and go boom!

 

[Greywolf]

Thanks for the warning!
anyways yea it sounds more complicated then i expected, but not impossible. Hey who knows if i build it, it might actually work
But i have another question, am I able to do this without using explosives? A way for me to make the pulse without blowing out the coil and magnetic field with it? that's a big concern

 

[Alexander]

Key in all pulsed projects (lasers, discharges, guns, etc) is BIG and FAST RELEASING energy storage = big fat low inductance capacitor bank.

By the way, when doing rail gun don't even bother to use heavy projectiles - they won't move at all with your few Joule bank. Use shorl light thin wire pieces - those fly good.

Also, induction gun could be fun ring launcher. All you have to do is to wrap ~ 200-400 turns of 0.15-0.25 mm coil wire (from Radio Shack or hobby store, or from old power supply transformer) around 1/2" x 7-10" steel rod (start near one end, fill half of rod only). Any smooth Fe rod will work (big nail, deck bolt, ancor concrete rod, etc) and even not very smooth (reinforcement rods) if you wrap a few tirns of paper around them to make them smooth. There are plenty of rods in h/w stores. You don't need a capacitor bank for this one - just plug it briefly (less than a second) into 120 V AC outlet. Coil takes a lot of current and gets hot quickly, so let it chill for a minute or so before next lounch. In shoots short rings of well conducting materials (Al, Cu) about 15-20 feet up and 50-70 ft horizontally. Rings are just short (few mm) cuts of 3/4 - 1" pipe (pipes can be found in plumbing, h/w or hobby stores).