How to create electromagnetic interference?

The ballast creates a magnetic field all around it. The arc in the tube creates an electric field all around the arc. Both, together, will cover a huge spectrum of noise.
I had to fight that several years ago and could only work with an Arduino when the light was OFF!

EMI generator kits:

Yes, there are also YouTube videos on bomb making, and how to commit suicide, don't be so faceasus.

Noise is AC, get over it.

Hi @pourduino;

in my younger days to generate noise on radios and annoy friends (or would they be enemies), I used a simple square wave generator.
The square wave is formed by the sum of the harmonics of a basic frequency, and so it contains a lot of different frequencies.

RV mineirin

We used the old fashioned mechanical buzzer, the one with a clapper and bell. You can also create something by taking an old relay and wiring the coil through the NC contact. When it powers on the contact will open, the relay shuts off, the NC contact connects again and the relay energizes. A short piece of wire will give you lots of noise.

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That is a great idea. How long will the relay survive this?

In the very early days of my electronics career in the late 60s wh had a machine for testing the susceptibility for interference. By today’s standards it is a safety nightmare.

A quarter horsepower mains motor was connected to the live connector of a mains plug and a hole was drilled in the plug exposing the neutral connector.

Then a rat tail file with a wooden handle was placed onto the neutral mains connector through the hole and the wire on the other end of the motor was striped up and down the file. This caused a few sparks but mainly turned the motor on and off generating the interference.

The thinking was that if the industrial controller we were making could withstand this it was good.

Note no numbers to back this up, but that was the state of play in those days.

Not exactly a safe procedure.

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You said "Between the arc and the magnetic flux from the ballast" in your first post. Do you mean the arduino (or the long input wire) has to be places between the lamp and the ballast? Or was that just a figure of speech?

Will this work if I for example PWM a 1A LED light? I've done high amp square waves before and my speakers never picked up any noise. I haven't investigated it's effect on arduino inputs tho.

This is what I did (link in my first post). I was using a ~30cm alligator clip. The relay started doing its oscillation thing but I got no noise on the arduino.

Well it seems from the replies that my linear wall adapter is actually my best option. Just plugging it in creates a crazy amount of noise. There's no sparks tho. It actually has a transparent case and I don't see no sparks inside, and none on the prongs either.

And I bet at the time you considered it a perfectly reasonable way to test.

I think "affordable" might be more appropriate!

Well actually to be honest it scare the shit out of me.

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That depends on the relay and how long you run it. I have been using an old klunker for years but it only gets a few hours now and then. I forgot to mention, take the bell of the buzzer thing they last a long time.