On Fri, 12 Jan 2007 04:16:37 GMT, distatica
wrote:

Don Kelly wrote:
"distatica" wrote in message
news:jRBph.624538$R63.323581@pd7urf1no...
default wrote:

snip

Like another responder already said an alternator is a better bet if
they can be found in land fills.

What you could do with your motor is vary the one field you do have
with a regulator to maintain the output voltage constant with motor
speed and loading. But then you probably won't find the parts for a
solid state regulator in the land fill (?). So that calls for something
more clever (or ancient) like a coil that
senses voltage and lowers the field strength by opening contacts when
the output exceeds a predetermined level. What do you hope to achieve -
charge batteries or provide DC power for
lighting? Is regulation necessary and why?

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Thank you both very much for your responses. I was worried that I would be
needing the 4 coils but no one would answer me on that issue, so thank you
for clearing that up. And a resistor does seem like a dumb idea in
hindsight.

I was trying to avoid the use of an alternator (although I can clearly see
this is a much better idea, especially a GM alternator with a built in
regulator). The problem is my access in the city to one, and my budget.
While I may be able to scrape enough money together to purchase a used
alternator from a scrap yard, I doubt I would have the necessary cash left
over to send it in the mail. However if this is going to output a useless
voltage there's not much sense in doing it either. My parents (and myself
to a lesser extent) are afraid of taking power and putting that into a
device without knowing what will happen, which is smart.

What do you hope to achieve - charge batteries or provide DC power for
lighting? Is regulation necessary and why?
I believe I have come to the conclusion I need to purchase an alternator
and send that, although I'm worried it's going to be one big box in the
end. I would like the system to charge a small lead acid battery and use
the battery as a regulator of sorts. Of course the alternator I pick up
will include a built in regulator. I would like if in the end they were
capable of using the creek to power/recharge their cell phone.

My biggest confusion at this point comes from dynamo flashlights, the
one's you never use batteries in. I have taken these apart and they look
like a very simple DC motor with some gears for higher RPM. If this is the
case how do they get all that power out of them to power a radio or 3 high
intensity LED's? Is it a transformer of some sort? I'm not sure what is
going on there. I looked at another flashlight that had a magnet moving
through the center of a coil when you shook it, it claimed to have a
capacitor that could be charged thousands of times, but when I applied a
voltage to the largest capacitors I had around (from microwaves) I was
only able to light an LED for a couple seconds.

Exactly how much usable power can you get from a small DC motor like that?
This would be a great alternative to my design... And since I have seen
hand-spun Motorola battery chargers I assume it's enough to power a
cellphone.

I will however be using a creek and/or wind to spin the DC motor, not by
hand.

Once again, any information is very greatly appreciated.

It's hard to say how much you can gain but trying to convert a series motor
to a compound generator would require adding a shunt winding (likely not
enough space for it) and also reducing the series field considerably (either
by removing turns or by using a low resistance shunt across the field
windings. Tain't worth the effort. As for the hand crank generators- they
are really low power devices- a LED doesn't take much.


My understanding is that the hand crank generator is the same as a DC
motor, and that is what is used for the generator. If I am incorrect
please respond, if not don't bother responding I'll take no news as good
news and we'll let this thread die. Thank you very much to those that
responded, you've been very helpful.

Hand crank generators are good enough for cell phone charging -
although it will take more effort cranking to charge a battery as
opposed to lighting an LED.

Someone just gave me one of those LED crank type lights and I promptly
took it apart. Inside was a large gear turning a small one - that
spun a "motor" like device with a set of rectifier diodes on the
output - so I assume they are spinning a few rare earth magnets past
coils for power. An alternator. There were also 4 rechargeable cells
in it and a switch. It says it will light for an hour with one minute
of charging - it probably does - stays on for hours at a time. So,
this one I have isn't DC it is an alternator.

When I was a kid - long ago there were these flashlights that you
squeezed and they produced light for a few seconds. You pushed on a
sector gear with a spring return (the teeth of the gear were visible)
that, in turn, spun some gears to increase the speed of rotation and
spun a little DC motor. The gear mechanism had a device that would
disengage the gears on the return stroke so inertia would keep the
motor turning while you got ready to squeeze again - no storage
battery lots of exercise. Small incandescent lamp. Well made and
inexpensive, but not too practical. They had DC toy motors in them
and produced DC to light the light.

If you are interested in charging lead acid batteries - you won't need
a regulator unless you tap into some significant power source with a
real generator or alternator. You would still need a diode or relay
to prevent the generator from discharging the battery when it isn't
turning.

Streams have to have some fast flowing water to be good candidates for
power generation. Fast flow means large change in height over the
course of the stream.

I've been tinkering with this impulse motor that would probably charge
a battery for lighting. The idea is to mount a magnet or two or more
on a wheel and spin them by a coil. The magnets induce a voltage in
the coil which turns on a transistor and another magnet which, in
turn, kicks away the magnet that induced the voltage and once rotating
it continues to rotate.

It would be a practical generator for something like charging a
battery for LED lights and cell phones. The wheel my magnets are
mounted to is 20 centimeters in diameter and weighs several pounds -
two ball bearings on a 13 mm shaft. As a motor it spins at a mere 120
- 200 RPM. The two magnets are 25 mm X 6 mm disks and very strong
(rare earth). As the magnets pass the coil they light an LED as well
as turn the transistor on - the voltage has to be greater than 4 volts
to do that.

My sense coil (the one turning on the transistor) has ~2,500 turns of
32 AWG magnet wire on it - very little copper - but very fine wire.
The core is a bundle of steel wires 12 mm in diameter and 75 mm long.
The DC resistance of the coil is about 230 ohms. There's a 6 mm gap
between the magnets and the core of the coil as they pass it. More
turns of wire or higher speed and it would generate more voltage. But
most of the cell phones I see here require about 5 volts to charge so
it is pretty close as-is.


A stream moving at 41 meters a minute spinning paddle wheels with no
gearing would be enough to provide useable energy to charge a cell
phone.

If you can get some rare earth magnets for a reasonable cost they
could be incorporated in motors to provide a rotating field and you be
making alternators from motors. I paid $20 for ten of the magnets I
use. Probably be easier to just chuck out the motor armature or save
just the shaft and turn a wooden cylinder to hold the magnets. A wood
turning lathe is easy to make from scrap and can be muscle powered.

My motor uses only two magnets (now) but I could just as easily mount
all ten to the wheel and have it spin much faster (or generate more
power). That's my next experiment . . . then I think I'll get a
smaller lighter wheel and see how little current I can get the motor
to run at. (right now it takes a pulse of 5 amps at 20 volts to turn
200 RPM). The drive coil (around the same core as the sense coil) is
about 500 turns of 22 gauge wire - and only 4 ohms of resistance)

Some guy is selling a bicycle tail light that uses a coil mounted to
the bicycle frame and magnets mounted to the spokes - it lights red
LEDs - more magnets, coils, and LEDs and it would be a practical
headlight - and more expensive.

White LEDs can be bought from Hong Kong for $12/100 post paid. A
pretty good deal compared to local shops here.

Search for "home power" the phrase - lot of good information on small
scale power generation.

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