oscillating electromagnet

A simple solenoid can be created by wrapping wire around a metal rod and passing current through the wire. The two ends of the rod will acquire a positive or negative charge that is dependent on the direction of current flow. Therefore, if you apply an alternating current, the poles on the magnet will oscillate at the same frequency. Incidentally wall sockets use alternating current that oscillates between positive and negative, so this should provide the desired effect.

See, I was told not to use outlet power though, due to the risk of shock and short circuiting. I'd be fine as far as short circuiting goes if I throw a resistor into the circuit though, right?

I knew about the solenoid thing btw I used a steel bolt and wrapped 20-30 feet of 22 gauge wire around it, rotating it with a drill.

How fast do you want the oscillations? If you're using line frequency, you're going to have very fast oscillations. At 50Hz you're looking at 10mSec in one direction followed by 10mSec in the other direction. You're definitely not going to hear individual plucks at that speed.

Well, like I think I said, I don't mind if I can't hear individual plucks, as long as it makes the bass go.

I would like input about the circuit oscillator solution btw.

oscillator basics

You don't want to be connnecting line voltage to an electromagnet, and a resistor is a very crude and inefficient way of dropping voltage.

I assume a transformer would be good then, to drop the line voltage?

Also, that site is the exact one I saw that made me wonder if anything would change if my load was an inductor as well.

Well I don't know, you are going to want a good deal of current to make that electromagnet strong enough to move the wire. So you might be better of to just rely on the impedance of the wire, and use a lot of coils, rather than dissipate your available power in a resister or something.



But 50 Hz is well within the audible range

Well, your load is an inductor-that's what a coil is. The best way to see if various electronic circuits will work, is to try them. You don't learn about them from reading.

Yes, a transformer to drop the voltage, a rectifier to convert it to DC, a filter to smooth the ripple. You should be able to buy a unit that does all three. There's some great regulated power supplies available that aren't too expensive.

I think one of the things I haven't been quite clear enough about is that I do have a working oscillator hooked up to a power supply, and that I can tell the electromagnet is working because of the interference picked up by the pickups. The only problem seems to be that the strings aren't moving.

It's probably too high a frequency for the strings to be able to react to. Have you got any capacity to change the oscillation frequency?

Yes, I haven't measured it, but iI think it goes from about 1 hz to 12 hz depenidng on how I set the variable resistor(I pillaged it from an old electronics kit, so I'm not entirely sure).

I figured it was just too quick of a pulse, not so much that the pulses were too frequent. Is there any way to fix that?

You're talking about lengthening your wavelength. My guess would be that there is a way, but I can't tell you specifically how. My knowledge is very generic. I'm an electrician, not an electronics technician. Access to a CRO and some components is how I'd go about it. Maybe some capacitance in the output stage, but that's just a pure guess.

Relying entirely on the impedence (or resistance) of the wire will most likely leave him with a huge winding. At typical line voltages he'd need several thousand feet of wire to get there.

But the point about making the magnet strong enough is, I think, the real issue here. A guitar string is under quite a bit of tension and I'm not sure that even steel strings have enough ferrous content to allow them to respond to a magnet without a huge magnetic field. (Many "steel" strings are actually nickel wound and the nickel wouldn't respond to a magnet at all.).

I didn't even consider the iron content of the strings. Try holding a normal bar magnet near them, and see if they'll respond.

Yes, you would need a good deal of wire to reduce the current via internal resistance...but as you point out, it's going to take a hell of a magnet to move a taught guitar string to begin with...assuming that it is even magnetic enough. Once you get enough windings to sufficiently move the string, start adding resistors...I don't see anything wrong with that concept.

Why you would want to drop the voltage and rectify and smooth it is beyond me....as we have no need to power complex electronics, and we WANT an AC signal for the switching anyway..

Inductive reactance will contribute to current reduction too.

The thing is, if possible I would like it to run off of batteries, and be of a reasonable size to hold in one hand.

A short summary of what I've done so far

1st: I wound 3 layers of 1mm diameter wire around a roughly 65 mm section of a 3 inch(76.2 mm) and hooked 3 9-volt batteries up to it in series. Then, I opened and closed the simple circuit by tapping one end of wire rapidly to the battery. The guitar string moved sufficiently to be picked up by the pick-ups.

2nd: I wound about 3 layers of about .3 mm diameter wire around a 65 mm section of a different 3 inch nail and hooked it up again to my 3 9-volts, and once again the tapping method sufficiently moved the strings.

3rd: I wound about 760 cm of .3mm diameter wire around a 6.7 cm section of a .9 cm thick bolt and hooked it up to 4 6-volt batteries connected in parallel. The tapping method produced noticeable plucks, but also noticeable electromagnetic interference in my pick-ups.

4th: I constructed my oscillator circuit from pillaged parts out of an old electronics kit. The circuit oscillates just fine, as I tested with a pair of headphones that made pronounced clicks at a frequency from maybe about 1 to 12 hz depending on where I set the variable resistor.

5th: I replaced the headphones with my electromagnetic bolt, and hooked everything up. I can hear electromagnetic interference in the pick-ups, but the strings aren't moving enough to make noise.

Ideas I plan on testing soon:
1. more wraps of a higher gauge wire around a similar bolt
2. wrapping something iron around the string to provide more iron content.
3. attaching batteries in series instead of parallel?

I'd like to figure out how to change the duration of the magnetic pulse(I really think my biggest problem is that the pulse is too quick, but I have nothing to back that up with)

So what is your intent in building this?