# creating an electromagnet using my Amp / AC signal tia sal22

• posted

Greetings All

I have a pt1100 amp with an impedance of 8 ohms rated at about (1000 watts output power) and a toroidal electromagnet with the resistance of about 1 ohm. I'm doing an experiment with AC signals, audio and toroidal coils. I'm trying to see how much I can increase the magnetism inside the toroidal coil basically a donut electromagnet using AC signals.

The steps I use: I play a signal out my computer than it's amplified by the pt1100 amp which is connected to the wire wound around a donut shape. Like this

The problem I'm having is after I play the signal with about an 1 amp running through the wire the internal circuit breaker in the pt1100 amp gets tripped. Is there a way I can get all the amps to flow through the wire without tripping the internal circuit breaker of the pt1100 amp?

Please not that the goal is to get as much current to flow though the wires of the toroidal coil as possible to create an electromagnet without tripping the internal circuit breaker of the amp. At the moment I can't increase the windings. I tried putting a ceramic

100ohm 10 watt resistor in series with the coil to see if that would help but the change was barley noticeable .

I also tried making a glass water resistor but it looks like most of the current was dropped in the water doing electrolysis.

And also I can't use DC at this point.

PS: I'm using 18 gauge wire.

Tia sal22

• posted

On 8/21/2009 6:45 PM Rick T spake thus:

Nope.

The problem is pretty obvious, and I think you already know that you're overloading the amp. Measure the resistance of your toroid coil: it's a

*lot* less than 1 ohm, right? You do the math, as they say.
```--
Found--the gene that causes belief in genetic determinism```
• posted

"Rick T"

** That is not any kind of 1000 watt amp.

It is PILE OF SHIT that retails for \$89.

** Insanity.

** Duuhhh !!

Amazing it has not yet blown up.

** Insanity.

** Be of no help with toroid.

..... Phil

• posted

The amplifier you mentioned cannot deliver a "thousand-watt" output; that's what it's capable of at the *peaks* of an audio signal, into certain loads. It's probably less than half that continuous.

For AC signals, what's important is not resistance, but impedance.

And that amp almost certainly cannot deliver anything like 300 to 400 watts into a one-ohm load. Audio amps are almost always limited in power output by the amount of current they can deliver (so if whatever the current is, can drive 400 watts into 8 ohms, it can only deliver 1/8 of that power *at most* into one ohm, because the current will be the same.

Using a coil constructed according to that drawing, the magnetic flux will be confined to the iron core. Did you expect to have a (powerful) field in the "hole"? Because that won't happen. Toroids are preferred as cores for coils and transformers *specifically because* they confine magnetic fields better than other topologies.

What did you want/expect to happen here?

It's probable that you need either more turns or a higher frequency (assuming the amp can handle that).

The way to maximize current *using the amp you mentioned* is to get enough wire on the toroid to make the load look like eight ohms (and note that's *impedance*, not just resistance. And, you have to make sure the wire you use has a large enough cross-section to handle that amount of current (probably seven or eight amps *if everything works out*). The next issue will be to make sure you don't saturate the toroid (ask it to carry a larger magnetic field than it's capable of).

As I said, even if you get a lot of current to flow, there will be no

*external* magnetic field, possibly except for a bit of leakage.

A series resistor may stop the breaker from tripping, but it will do that by limiting the current, which is counterproductive if you want a powerful field (the strength of which is proportional to the current times the number of turns on your coil).

That would not produce an external field either.

The wire gauge is not first-order important here. It just gives you a clue as to how much current might produce how much heating at some specific frequency.

If you're genuinely interested in pursuing this project, I suggest you do a bit of reading. Start with the relationships of resistqnce, reactance, and impedance -- what they are, and how they are measured; check into magnetic saturation and why it's a good idea to avoid it; learn what the specs of that amplifier *really mean*, so you'll understand just how much current it can actually deliver (at different frequencies). Then you'll be much better equipped to get something working that does what you want it to.

Isaac

• posted

**BZZZZTT! Wrong. Given the abscence of real specs, I would guess that your amp can deliver no more than 50 Watts/channel.

and a toroidal electromagnet with the resistance

**Define "toroidal electromagnet". Electromagnets are NEVER toroidals. Are you attempting to use a toroidal transformer as an electromagnet? You are doomed to fail.

I'm doing an experiment with AC signals, audio and

**Why? What frequency?

I'm trying to see how much I can increase the

**Won't work with AC signals. Go read a text book on the subject.
**That is not an electromagnet. It is a simple inductor.
**You probably already are. Your pitifully crappy amplifier does not like the abuse.
**Then stop wasting your time. Go study some texts on the subject.
**Doesn't matter what you are using. Whatever you're trying to do is doomed to fail. Well, unless you want to destroy your POS amplifier. On that aspect, you are on track to succeed.
```--
Trevor Wilson
www.rageaudio.com.au```
• posted

You need to use a variac.

• posted

**A risky move to suggest that a moron like this use a (non-isolated, presumably) VariacT for such a doomed project. Still, maybe it's the best thing for society as a whole....
```--
Trevor Wilson
www.rageaudio.com.au```
• posted

[etc]

Huh. Are you related to Phil Allison?

```--
Wim Lewis , Seattle, WA, USA. PGP keyID 27F772C1
"We learn from history that we do not learn from history." -Hegel```
• posted

**No. Why do you ask? Did I use profanity in my post? Was I accurate and succinct in my points?
```--
Trevor Wilson
www.rageaudio.com.au```
• posted

No matter what, virtually every point that Trevor made in that post is true.

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