Yea, very true. Could you use it to charge a big ass capacitor and discharge the capacitor quickly for high current devices? I'm asking because I honestly don't know.

Also, just as a side note, and not to argue, but say you were to use a super small gauge wire on the lower side of the transformer, such as 36 AWG. Then on the high side, could you use like 0 AWG to get lower resistance and thus a higher current while maintaining the same voltage? Bigger gauge has lower resistance and since V = I * R, if the R value goes down, I has to go up if V is to go up. I don't know exactly how much this increase is in reality, so if someone could clarify that I'd really appreciate it.

Oh, and you don't need heat dissipation in the liquid really. as long as you have adequate airflow, the pump will cool itself, and the water isn't actually touching the generator at all. All it's doing is spinning a fly wheel.

Oh, and a good example of what I'm trying to do is a water wheel outside an old mill. The way those work is by spinning slowly, and through gearing they got machines running quite quickly. The water supply is endless, and thus the power generated was endless as well, even though it was a small amount.

Forgive me if my idea is retarded, its just me thinking wishfully to distract myself from the horrendously redneck town I live in.

 

Your home-made generator will have low output power. Low voltage and low current. Its AC can feed a transformer and the transformer will stepup the voltage but the current will be reduced by the same amount so that the power remains almost the same.

It can be rectified and used to charge a capacitor. It might take a week. Then the capacitor can give a single momentary pulse of power to something and the capacitor will need to be charged for a week again.

Some electric motors make good generators. A powerful generator is described on the internet and uses a motor from a furnace fan. It doesn't have magnets but uses the residual magnetism produced from the last time it was used as a motor and the magnetism becomes very strong each time it is used as a generator.

The manufactured motors and generators use laminated iron cores, not just air.

__________________
Uncle $crooge

 

I don't know; there seems to be a fairly large community of people building these things, especially in DIY wind generators. ive been doing some more searching and have found more people documenting the same or similar design, with claimed power outputs of 300 to 1000 watts. (one is Low RPM Disk Alternator but there are others if you dig around a bit. Hugh Piggot is a good name to search)

if the power output is so very, very low, then how do you explain the operation of hand-held "shakeable" LED flashlights? all that's doing is shaking a (small) magnet through a coil (not particularly fast either, human shaking speed), and a few seconds of shaking will light several LEDs quite brightly for a considerable amount of time. furthermore, the magnet inside them is strong, but not so strong as to stick you to a car or a fridge or something if the thing is in your pocket, which is certainly possible with the size of the magnets i'm looking at. (a 2"x1"x1/2" NdFeB can have upwards of 200lbs of pull if its a good quality one).

i don't know if you've had any experience building anything like this, if perhaps you even work in commercial generator design, i don't know, but so far you havent given any reasons why it should fail, other than "the coils make heat." everything ive read shows that this is not a significant problem. otherwise you have simply said that "it won't work."

 

Bryan on this forum made his wind gererator from the motor of a washing machine. It works very well.
A do-it-yourself generator cannot compete with a manufactured one.

The article you posted uses an 8-foot diameter windmill to power the generator. You have a small amount of water to slowly spin a little one.

Many "shake-lights" cheat and hide a little battery inside. It lights a few LEDs dimmly. I have never seen a bright shake-light and the light doesn't last long.

EDIT:
On the internet is a do-it-yourself generator powered by a hampster. It charges a battery then lights an LED dimmly for a couple of hours like a solar garden light.

__________________
Uncle $crooge

 

oh, hah, this whole exchange was for nothing, i wasnt the guy who posted about the water wheel thing (it really wouldnt be particularly useful...). no, i actually am considering hooking this up to a windmill, and i do plan on making it a fairly hefty generator. just, instead of 300-1000W i'd be happy with 30-100, so I can scale back the magnets a little bit. this isnt a desk-sized thing

i said i was considering water power as well, but certainly not a fish tank pump, i mean like constructing a small dam in a brook near my house...

back to my original question, how do I find out the actual field strength of magnets? can't seem to find it anywhere... perhaps I would have to buy a meter and try it out on various ones

 

The K&J Magnetics site posted by RadioRon has specs like this:
Do you need something different?

__________________
Ron

 

oh, missed that one, thanks (caught up in debate, lol)

surface field is exactly what i want

 

Those magnets are so powerful that they say if your skin gets pinched between two of them then they can't be pulled apart.

__________________
Uncle $crooge

 

A wind generator isnt a bad idea. and you didn't really say how big the project you had in mind was going to be, so I went with something small because its cheaper.

The shake-able flashlights are not really run off batteries. This defeats the purpose of the "Shake". Also, depending on what kind you buy, some are indeed quite bright, and the light output isnt designed to last for hours upon hours. All you have to do is shake it a little though and it will be good to go. They are designed to save you from buying batteries, or having dead batteries when you need the flashlight.

 

yeah i didnt really specify because i wasnt sure, needed to find magnet strengths so i could see what was possible. like i said above, the more i think about it the more i want to design something around 100W

 

Here is an Instructable with photos of a fake shake-light:
http://www.instructables.com/id/Salvaging-a-$1-Fake-Shake-Light/

It has two coin batteries that light its LED dimly.

__________________
Uncle $crooge

 

A review of the expensive shake-light made by guess who says it is not good:

Attached Images

shake-light.PNG (39.6 KB, 8 views)

__________________
Uncle $crooge

 

Hello

Here's a link to a diy double magnets generator, you may find somes more ideas.

DIY 1000 watt wind turbine


Here it's a link to a place to buy parts;

Wind Generator Plans, Free


For myself I did use neodynium magnets from old big computers hard disks.

Bye

Gaetan

 

Here is what I'm talking about.
ShakeLight:60 battery-free LED flashlight magnet powered shake light

you use capacitors, not batteries, to store the charge. The capacitors have a slow drain rate because the load is almost nothing, and thus you can light the LED for quite a while before you need to recharge it.

 

The same review that I posted for the ShakeLight 20 tested the ShakeLight 60.
They are almost the same. The capacitor discharges quickly. After less than 1 minute the light was half. In 5 minutes the light was about 8% and dim. In 30 minutes the light was very dim and in 60 minutes the light was almost zero.
Flashlight Reviews and LED Modifications

Attached Images

shake light 60.PNG (7.5 KB, 0 views)

__________________
Uncle $crooge