3.5mm Headphone Jack LED?

[ssniesle]

Is it possible to make a LED flash with a standard 3.5mm headphone jack as the only power source?

I was thinking that you would do the following:
1) write a program that would maximize the output from the headphone jack.
2) Use a bridge rectifier to turn the headphone jack from AC to DC.
3) Use a transformer to bump up the Voltage to 1.7V
4) Use a capacitor that will eventually light the LED

Does this make sense and if so how would I calc the values.

Thank you

 

[khankll]

Transformers do not work on dc the only work on AC.

 

[davenn]

What is the headphone jack connected to ? presumably some sort of music source?


D

 

[ssniesle]

iPhone to drive LED

Khankll, yes you are right. I would have to transform the AC before converting it to DC.

Davenn, i would like an iPhone to power the LED and have a custom song/app manipulate the output.

I was also considering using a battery to drive the LED and connect the audio output to a transistor and use it as a switch....comments?

thanks

 

[BobK]

The second method is a lot better. I doubt that there is enough power in coming out of the headphone jack to directly power the LED.

Bob

 

[Mongrel Shark]

It's almost do able.

I just measured a headphone jack. 0.24v @10 micro amps.

I know of joule thief's that will do one or the other but never seen one do both at once.

Lidmotor's "Penny Ossilator" modified with a germanium transistor might do it.

This one need's .5v but it's using silicon transistor...

I am working on getting LED's to light off similar power levels myself. Been looking at germanium transistor data sheets for days.



Please let me know if you find a good one that will run on low current. Best I can do is 700 micro amps from .2v

If you can make a custom app. You might be able to push a few more micro watts.....
[edit] You could get a lot more power if the device has a USB port

Good luck!

 

[BobK]

If your calculation is right, there is no hope.

.24V at 10uA = 2.4uW

Typical red LED 2.0V at 20ma = 40000uW = 40mW

But I think it is wrong. A typcial headphone amplifier puts out about 50 to 100mW, which is enought to light even the ineffiecient LED above.


Bob

 

[Mongrel Shark]

You could be right Bobk. I measured the output on my laptop, which is not the loudest headphone jack. I didn't feel like pulling screws out of my speakers and didn't have a jack to check it there. Although I would expect my laptop would be similar to an iPhone etc... Using an amplified jack seems like cheating..

And I can light that led at 50hz from less than 1v@500uA with blocking oscillator.... So visible (very dim) light from .0005w or even less. I'd do a video, but I don't have any low volt led's. 3.2v is the smallest I have..

I have a video up as of 12 hours ago. Where I light a 3.2v 20-40ma bright white led from less than .2v @ 800ua. So .16mw or 160uw... Transistor is less than ideal. running at over 7khz. if I can slow down the flashes. I can get more visible light from less power. Although my LUX meter can tell the difference, my eyes don't notice.. 1v@55ma was actually hurting my eyes...

If you have 1mw or more. No reason you can't flash a led. If the flashing is supposed to be detectable by eye (ie less than 30hz). You could get a bit of brightness in a low power led...

 

[KrisBlueNZ]

I'd say it would be possible.
You'll get twice the power if you bridge the left and right channels by driving the left and right outputs in antiphase, with say a 1 kHz sinewave or squarewave, and connect a transformer primary between the two signals.
Use a turns ratio of around 1:20 or so, using fine wire on something like an RM5 or slightly smaller with a moderate permeability core, and rectify the output using a bridge with low voltage drop - you can use germanium or Schottky diodes, or an active bridge made from four MOSFETs (see http://www.irf.com/technical-info/whitepaper/TP-080527.pdf) if there's enough voltage, or perhaps just connect the LED straight across the secondary (with a small current limiting resistor, maybe) for simplicity.
You can get red and green LEDs that light pretty brightly at just 1~2 mA forward current.
Some trial and error will be required though.
More details? Just ask.

 

[Ben144]

Hi Please help me, I have the same question. Does anyone know how this could be done? I was struggling with my neck injury, making circuits to do this but I dont know what I'm doing and suffered a lot. (car accident)
Im trying to make a healing device that just outputs an audio signal as a LED oscillation.
THanks

 

[davenn]

Im trying to make a healing device that just outputs an audio signal as a LED oscillation.

and how is that supposed to work ?