help kids science project

[sigpro2340]

Hi all
i'm new to the forum and need some help with my son's science fai
project that I thought was going to be a no brainer.

The project was a simple wind turbine to generate electricity to mayb
power a little led light or something. I read online we could use
little dc motor to do this...well yes it works but the blades do no
spin fast enough to make enough electricity to lite the lights righ
away.

So..i thought..why not run the motor to a set of rechargeable A
batteries then to a switch...and then to some little led lights. I
is the same idea as far as generating electricity..except it is bein
stored for later use.

But then i thought..if i wire the motor right to the batteries....wh
is to say the batteries wont keep powering the motor.

So basically...what i need help with is how to wire this...and wha
else do i need besides what i have which is

a 9-18v DC motor i think max is 18000 rp
2 AA batterie
some small 2 volt led light
a toggle switc

i know i'm going to need some sort of diode..but not sure what...thi
is where i need help...please!!!

Ro

 

[mc]

Have you used a voltmeter to determine what voltage you are getting out of
the generator? It has to be higher than the battery voltage, or the battery
won't charge. Also, the diode (I suggest a 1N4001) will cost you an
additional 0.7 volt. That is, if the battery is charged to 1.4 volts and is
charging through a diode, the generator will have to output 2.1 volts.

Voltage is like pressure -- it determines which direction the current flows
in. (Like water flowing from the higher to the lower pressure in a system.)
Current (amperage) indicates number of electrons per second (the number of
electrons per second in one amp is gigantic).

 

[Dorian McIntire]

So..i thought..why not run the motor to a set of rechargeable AA
batteries then to a switch...and then to some little led lights. It
is the same idea as far as generating electricity..except it is being
stored for later use.

But then i thought..if i wire the motor right to the batteries....who
is to say the batteries wont keep powering the motor.

So basically...what i need help with is how to wire this...and what
else do i need besides what i have which is:

You really have two choices to simplify the project and keep it from turning
into a Rube Goldberg machine.



1) Use a high torque, low rpm motor. An 18000 rpm motor will never give you
enough voltage at a low rpm. Most rare-earth magnet motors will provide
ample voltage at low rpms.



Many pancake style stepper motors, used in older hard drives, will drive a
LED at low rpms and have multiple phases which helps create constant power
throughout a 3 or 4 phase cycle. I've seen people create artistic windmills
out of these motors which produce a wonderful light pattern on the windmill
using LEDs when the wind blows.



2) Use a gear drive or belt drive to take the relatively low rpms of the
propeller to match the requirements of the higher rpm motor. This is how
most working wind generators work.



Dorian

 

[flank]

Ron,
Before I try to steer you away from your project, I would like to
say that it is an excellent idea for a project...but not really a
beginner project. The problem is that unless you are using very large
blades, it is very difficult to get wind to produce electricity. But,
a simpler project which will demonstrate similar principles is to build
a hydro-generator. So, instead of using a windmill, you can make a
watermill. I jugded a science fair last year where a kid used an
aquarium, an aquarium pump, a small DC motor, and a set of Tinker Toys.
The aquarium served as the pump reservior; the pump was used to shoot
water onto the blades of the water wheel - made by Tinker Toys. He
used a DC motor which was wired through an ammeter to a small voltage
light bulb (6V I think). He used a voltmeter and the ammeter to
determine power output. He changed the angle of the water stream to
change the power.
If you decide to go with this project, and you need any details,
please let me know.

flank