DC generator for LED

[Othello]

For a small experiment I am trying to hook up a strong magnet and a coil as generators to light up an LED.
The magnet (or the coil) should only be moved by hand to produce the voltage to light up the LED.

I am asking what coil I should start with?
As the number of turn goes up so does the resistance and losses.
Maybe someone here has an idea for a starting point so I wouldn't have to experiment tooo much.
Thanks Uwe

 

[Overclocked]

For a small experiment I am trying to hook up a strong magnet and a coil as generators to light up an LED.
The magnet (or the coil) should only be moved by hand to produce the voltage to light up the LED.

I am asking what coil I should start with?
As the number of turn goes up so does the resistance and losses.
Maybe someone here has an idea for a starting point so I wouldn't have to experiment tooo much.
Thanks Uwe

Old Motor from a Treadmill or Washing Machine. Even an Old Fan would work (with the blades removed) and a hand crank attached. You would just have to rectify the signal and filter it

 

[Othello]

Well, I was thinking about something much smaller.
A very efficient tiny generator which could just light up an LED (order of magnitude would be around 1 mW).
As a generator a wind driven membrane, like in a loudspeaker.
I just lit up an LED using a speaker but it still needs too much of an effort...
Uwe

 

[stevez]

This seems like a project where you might do some engineering to get yourself in the right ballpark. Current/voltage requirements would be a good thing to define. I'd suggest starting at the lowest you can - so experiment with some LEDs to find the minimum. You might then try to define the generator end then construct a model of convenient size - and measure what you can get out of it. Don't worry about the LED - you compare your needs against what the model will deliver and go from there.

If wind is your source and a speaker represents what you are thinking of as a generator keep in mind that the speaker does nothing with steady pressure - it's only movement of a coil in a magnetic field that will produce a flow of current. Keep in mind that the matching of generator impedance to the load may be something to keep in mind. A crude example - the generator might be most efficient in delivering 10 volts at 2 ma and your LED may require 10 ma with 2 volt drop. Power is the same but it's not a match.

You could step back and look at the physics to get some sense of the capture area you'd need - how much wind you'll need to obtain the desired result - then apply some judgement on relative efficiency as a way of finding a starting point for the generator. If you were planning on a rotating cup mechanism to capture the steady flow of wind it's not too hard to establish the approximate cup size - if you know the wind velocity you also know the available pressure (the velocity pressure) to move the cup.

I hope this helps.

 

[Othello]

Well, Stevez, I like that organized thinking and I need it for this project.
I started by getting some idea about my detector, the LED.

I could light one up at about 1.5V @ 1 or 2 mA. That means about 3 milliwatt of power.

And leaving impedance concerns aside for the moment (even though they are important) the question is now what is the minimum area and windspeed to power this LED.

The problem I can see is that the generator, a powerful little magnet and a coil for example, will only have a limited rate of change of the magnetic field (sort of your rpm) and therefore I must optimize the coil to make the most of the little power I will get.

This is mostly the point I was hoping for some experienced insight from this forum.

Uwe

 

[mvs sarma]

Hi, use an old tape recorder motor(a one that has no electronic speed regulator) and rotate that you get DC voltage. from this you can salvage and make your own re- engineering, perhaps.

 

[Overclocked]

Well, Stevez, I like that organized thinking and I need it for this project.
I started by getting some idea about my detector, the LED.

I could light one up at about 1.5V @ 1 or 2 mA. That means about 3 milliwatt of power.

And leaving impedance concerns aside for the moment (even though they are important) the question is now what is the minimum area and windspeed to power this LED.

The problem I can see is that the generator, a powerful little magnet and a coil for example, will only have a limited rate of change of the magnetic field (sort of your rpm) and therefore I must optimize the coil to make the most of the little power I will get.

This is mostly the point I was hoping for some experienced insight from this forum.

Uwe

Well, the bigger the magnet, the greater the Magnetic Field, the more you can move the coil. HDD magnets are very strong, and so are magnets from a Microwave. Magnets from a microwave seem to have more "reach" than a HDD magnet, but a HDD magnet has a stronger field with a bit of reduce reach.

 

[RODALCO]

An old stepper motor from an old printer or photocopier are great motors, to generate voltages at a low speed to drive a LED.