Turn any solid surface into an acoustic speaker system!

[BW86]

thats pretty cool

 

[0roo0roo]

Originally posted by: SwiftWind
The soundbug could do this a few years ago already....

yup not impressive.

 

[DrawninwarD]

I'd like to get one, but it's like $140 USD. Plus the sound quality would probably be mediocre. Just a novelty item I guess.

 

[JMapleton]

THAT MY FRIENDS is my next speaker system.

 

[0roo0roo]

Originally posted by: DrawninwarD
I'd like to get one, but it's like $140 USD. Plus the sound quality would probably be mediocre. Just a novelty item I guess.

it is mediocre and a novelty, i had a sound bug. theres good reason most speakers don't look like your desk😛 🙂 its no more convenient either, you'd get better sound from a portable speaker of the same size.

 

[Rubycon]

Originally posted by: RedSquirrel

Eventually I want to build a tesla coil, those look so fun.

24kW fart machine?

 

[Mark R]

Originally posted by: RedSquirrel
The only thing I wonder about speakers, electromagnets, transformers etc is how is it that they work, when all it is is a short circuit? Why is it that when you plug a transformer in, it does not trip the breaker or 48v speakers don't blow an amp? Do they add anything special to them such as big resistors? I'm sure if I twirl around wire around a nail and put it on a high voltage source, I will see a very nice light show. At low voltages it works fine but not high.

Transformers, electromagnets and speakers rely on a concept called 'inductance' as well as resistance to limit the current flow.

Inductance is resistance to change in current flow, and is caused by energy being stored in a magnetic field. When you apply a voltage to an electromagnet or a transformer, the current will actually gradually ramp up, because the inductance is basically giving the electrons 'inertia'. When you break the circuit by disconnecting the voltage, the electrons with their inertia try to keep going. Experiment: Get a AA battery. Take a wire and briefly short it out. Watch for any sparks. You won't see any, unless it's very dark and you're very lucky. Now get a small transformer (e.g. one stripped out of a wall wart) and this time short the AA battery out through the low voltage side of the transformer. You'll get some nice fat sparks when you disconnect, because the inductance tries to force the electrons along.

Now imagine what happens with AC current. You push the electrons one way, and the current gradually builds up. Then the AC current reverses, and the electrons get pushed the other way. The current now starts decreasing, and gradually reverses, and starts ramping up in the opposite direction. Basically, the current is limited, because it never has a chance to build up before the voltage reverses and started pushing the current back the other way.

E.g. I've got a 240 V transformer. The primary coil has a resistance of 6 ohms (according to my DMM), but when connected to 240 V AC, the current flow is only 10 mA. The primary coil's maximum current rating is 1 A. If I connected this transformer to a 12 V car battery, I would burn it out (as at 12 V DC the current flow would be 2 A).

The really clever bit about how a transformer works, is that if you allow a current to flow in the secondary winding - that current will drain the magnetic field in the transformer. The more current your circuit allows to flow, the more the magnetic field is drained. As it's the magnetic field that provides inductance, weakening the field reduces teh inductance, which allows a higher current to flow in the primary - so the current in the primary will rise to meet the demand of the secondary.

 

[YOyoYOhowsDAjello]

This thread needs more rotary woofer 😉
http://www.youtube.com/watch?v=E7Bkrypxzs4