Then the title is wrong.

Agreed, but the first post is clear what they want,
at least they are not chnaging the first post, and title during the posts as others have done with apparently mods agreement,

 

There are AC currents of many voltages and frequencies going through a coil in every loudspeaker. Why don’t they produce light?

Bob

Because it is a very low amperage. Also, the light may be observed by shorting a lithium ion battery, because the pulsed DC passes through the proper voltage.

Today I devised a very good filament. I will be using a zinc coated extension spring. It measures 6.3 ohms, so at the target 2.3 volts, that should allow about 300 mA of AC current. I am anticipating a green light.

 

I am anticipating disappointment.

 

I will share my results, even if it does not work. I purchased a cheap oscilloscope to possibly help.

 

A white LED is a 3.2V blue LED with a yellowish phosphor on top.
An old dim green LED used old chemistry and was 2.3V, but a modern very bright green LED is about 3.2V like a blue LED because they use the same modern chemistry.

Your filament will not produce green light. If it is tiny it will glow red hot then soon burn out.

 

Okay, I am not sure why you are bothering to say that. Clearly I am not certain of the results, otherwise, I would not be talking about it the way I am. I have been thinking about this idea for about 7 years. I am very close to actually trying. It is surprisingly difficult to create a 2.3 volt A.C. power supply. I think a transformer would not work, because the voltage changes gradually, and I require a fast voltage change at 2.3 volts.
I have already spent a considerable amount of time and effort. I find this very fun, even if it fails. However, according to my calculations, it should work very well.

 

the OP is looking for light from the LED, not the wire,
getting different colours from a red led by varying the voltage still wont change the colours ,
bu ti is the led,

Really, where is the LED in this description?

I am fairly certain it will work. I will be targeting 2.3 VAC at 300 mA. I will be generating a square wave with a 555 timer, which will activate a pair of zener diode voltage regulator circuits, one on an inverter, which will pulse at about 20khz through a ferrite core inductor with 3-5 turns.

He thinks an AC current going through a wire will produce light output. It could, if the wire is heated enough, but that is not what he is talking about.

 

I am not anticipating the filament will be hot to the touch.

 

Because it is a very low amperage. Also, the light may be observed by shorting a lithium ion battery, because the pulsed DC passes through the proper voltage.

Today I devised a very good filament. I will be using a zinc coated extension spring. It measures 6.3 ohms, so at the target 2.3 volts, that should allow about 300 mA of AC current. I am anticipating a green light.

A speaker taking 8W of power has 1A going through it. That is over 4 times the current you are "targeting".

The light you observe by shorting a battery is called a spark.

Bob

 

It must be exactly a specific voltage. Look either it will work or it won't. I cannot change the laws of physics.

I am fully aware that this idea sounds stupid. But it should work, and if it does, that would be pretty cool, and perhaps useful.

Saying it won't work does not help anything, except is rather annoying.

 

You have no idea what you are talking about. The energy dissipated in an LED is via a quantum jump, which can emit light. The energy dissipated in a wire carrying current is by collisions of electrons with atoms, which produce heat. Not at all the same thing.

Edited to add: Doesn't it occur to you that people have been overserving current going through wires for over 100 years and nobody has observed the type of light emission that you are expecting?

Bob

 

Why are you so offended? Are you willing to spend hundreds of dollars on equipment and hundreds of hours of work to try it? No? Well I am. So what is your problem? Bob.

I mean if I am wrong you all get to laugh at me. But really you are missing the point. This is really exciting to me, if I am right, I don't want to be the only one surprised.

edit. Yes, it has occurred to me, and seems, absolutely bizarre.

 

I am not offended. I am am a person with a physics degree who is trying to help you understand something. No desire to laugh at you, just set you straight. And save you lot's of time, money and disappointment.

Bob

 

Really, where is the LED in this description?


Hi @BobTPH

this is the orriginal post

Hi,
I am an electronics hobbyist. I have noticed that a common and boring component the Light Emitting Diode has a specific voltage drop across it. For example, a red LED has a voltage drop of 1.7-2 vdc. This is interesting, because it is the same value for the energy of a red photon (1.7-2 electron volts). Perhaps it is possible to generate a specific color of light from a low voltage AC current. Any thoughts?
Currently I am working on constructing such a power source to test it.

Agreed its less than straight, but its a LED that I read that the OP is talking about putting an AC voltage across,
But I could be miss understanding,

 

Ask him then. He has been quite responsive.

Bob

 

I am not offended. I am am a person with a physics degree who is trying to help you understand something. No desire to laugh at you, just set you straight. And save you lot's of time, money and disappointment.

Bob

I am already aware that it is not supposed to happen that way, is actually a little scary, etc.
I will be trying the experiment regardless of anyone's opinion. I am simply sharing my idea at great cost, simply for laughs.

 

Hey Bob, how do you explain the light emission from shorting a lithium ion battery? Those cannot be sparks, since the voltage is too low and there is not a sound. It is simply streaks of yellow and red light.

 

That is called a spark. It is produced by heating a small amount of the wire at the point of contact.

Bob

 

No, it happens instantly only after the contact occurs. If it was due to heat, you would see continuous sparks.

Tapping the leads rapidly produces a lot of light, but using a laser thermometer reveals no heat.

 

Since we seem to be engaged in actual conversation, can you explain some things to me?

Why several turns or wire on a torroid.
Why 20 KHz?
Why do you expect 230mA when you apply 2.3 V across a wire? Ohms law tells us the resistance of the wire would be:

V/I = 2.3 / .23 = 10 Ohms.

That is either a very long or very fine wire.

Bob