Question about EMP’s and prospective output.

Thread Starter


Joined Nov 24, 2023
Hi folks, I have a question about EMP’s.
As a hobbyist in electronics I do all sorts of little projects for fun and to learn. This is often after I’ve watched a “video” online that’s sparked my interest.

A year ago I set about making a small EMP with the aim of making something that would interfere with but not destroy electronics. In the end I made a circuit with a 3.7v lithium 18650 cell which powered a voltage step up coil (sorry don’t know correct name) that converts 3-9v into 5,000v-10,000v roughly. This high voltage then jumps a gap in the circuit and goes into an easy enamelled wire coil that then grounded back through the “voltage step up coil” and then back to the 18650 cell ground completing the circuit. This did work and when presented to an old smart phone or old tv in close proximity it would drive the lcd screen nuts but would return to normal when the magnetic field stopped. I was pleased with this project and it was fun.

Recently I learned how to strip and test a car alternator. Whilst doing this my brain wandered, as it does, and I had this thought.

What kind of EMP output might I get compared to my first project if, I used a 12.6v car battery to power a car ignition system coil pack which puts out around 22,000v, get this voltage to jump a gap into the single winding (electromagnet) that is on the rotor of a car alternator? Also would I need to remove the alternator rotors north/south magnetic pole claws given that I want to create an EMP and not an insanely powerful magnet?

Im essentially trying to gauge what output I may theoretically get from this. I know it’ll be more powerful but don’t have the ability to calculate how much.

Any ideas or advice is much appreciated.

Thread Starter


Joined Nov 24, 2023
The magnetics of an alternator would be designed to be contained within the device, so not much.
My intention is to actually dismantle the alternator, remove the rotor and disassemble it down to the single winding as I only intend to use the coil.
My understanding is the higher the input voltage the greater the output? The coil on the rotor has a fine wire of much greater length compared to my previous project and as I understand it that increases output also?
One thing I’m not sure about is whether to remove the claw poles or not? I don’t know what difference they make. Although I am just trying to harvest the coil from the rotor so to speak.


Joined Jan 23, 2018
It will not work to use such a step up because the high voltage can not deliver the current to provide enough of a magnetic pulse. An electromagnetic field is generated by current flowing, not voltage applied.
I investigated the physics of providing a really huge magnetic pulse quite a few years ago. The problem was that the high powered generator system needed to produce the pulse of adequate strength for the application were both massive and loud. And would need two or three diesel trucks to transport and several minutes to connect prior to the pulse. Such an operation could not be done "discretely" and un-noticeably.
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Joined Feb 24, 2006
To get a true EMP you need to research low yield nuclear weapon. I suspect you will attract the attention of homeland security before you can obtain the material and construct such a device.

schmitt trigger

Joined Jul 12, 2010
From your description, it appears that you are describing a Tesla coil. Photos and -gulp- a schematic of your apparatus would help.
Tesla coils disrupt nearby electronics and can even light up fluorescent tubes wirelessly.
Tesla coils can be scaled up significantly. Nikola himself built one on his Colorado lab that was perhaps 50 feet high.


Joined Sep 24, 2015
Years ago I was trying to solve a problem. My approach lead me to create something that did not do what I thought it would. However, just out of stupid curiosity I energized it and the microwave oven across the room shut down. I had something. Began testing it in different scenario's and discovered I created an electronic key that could open parking garage gates and let me park in the doctors parking area of the garage instead of the patient parking area on the top. In the sun. The HOT sun. The stifling hot sun. Then, again out of stupid curiosity I tried it at the security entrance. It opened the door. No, because it was a security entrance I did not go through. But the fact was - I COULD!

I've never described this project to anyone because of the dangerous possibility it could be used for nefarious purposes. So don't PM me, I won't tell you what I did or how I achieved it. Also, I no longer am in possession of the device. It's long dismantled and gone. And I'll never build another and I'll never describe the device in ANY sort of detail.

EMP can be considered a weapon. It could disable emergency communications, which could give a thief or terrorist an advantage. It could set off explosive devices. And a host of other socially unacceptable applications. Without reading the AAC Community guidelines I think discussing EMP devices along with Rail Guns and other potential weapons are a taboo subject and thus not allowed. I'm not an administrator, just another user of this website. I'll leave it up to them to decide if this thread is allowed or disallowed. But I must express my concerns that EMP could be employed by bad actors. Not saying you're a bad actor, just that someone you may not know might see this and decide they could have useful applications for causing havoc and potential ill gains.