Simple brake disk mini generator 101 question

[bryan]

hi this might sound too basic. I am building a water wheel for a small flow and so the generator will only output the energy of the water flow - and so I am not complicating things with a three-phase wiring. Its going to be a simple single phase. I believe that the 80 coils should be positive and negitive such that every other magnetic field is reversed? The magnets are arranged on a brake disk. should the copper wire coils be all the same direction? (identical) in series. What is a guess on coil turns considering ohms law? Would 30 be more efficient than 60 turns? its not heavy wire i thinks its 22 gauge or  24. I have the parts collected and the casing worked out, this pretty basic, so I would appreciate any correction if I'm making a mistake before epoxying it.

 I looked everywhere and I could not find the answer to my too simple question; is every other magnet on the disk reversed, are the coils identical, most efficient number of turns. This is for a trickle charger, maybe .5 to 1 amp at 15v max. (I can not expect such a small stream of water to simply turn the rotor too slow if it was made more powerful or fancy)  Thanks!

[electrondady1]

what is the dia. of the brake rotor.
how many magnets will you use.
what are the dimensions of the magnets.
what is the strength of the magnets  .
in single phase there is one coil for each magnetic pole
you can wind each coil in the same direction
 but solder them together reversing each second coil.
as in... start - tail / tail - start / start - tail / tail - start/ etc

if you can  use a  second rotating brake disk(even without magnets)  as a flux return path  it will increase the output.

 




 

[Flux]

One more vital question, what speed will it be running at ?

If this is direct drive from a water wheel you will struggle to get even 10W without significant magnets, if you are planning to get 80 on to a brake disc they must be very tiny.

Otherwise the advice given is correct, single phase may be as good as 3 phase in this application although it is really no simpler, just connected differently.

Flux

[bryan]

THANKS a lot for your help! the magnets are 30 mm x 3 mm. OK so the coil creates a flow of electrons simply because it is charged by a shift in the magnetic field that the coil is exposed to (and the speed of the change of the state of the coil).

If the magnets are reversed every other magnet... then I should also reverse every other coil? (start - tail / tail - start / start - tail / tail - start/ etc) ?

Yes, I am using a identical second rotor with magnets such that the coils are sandwiched between the disks on either side.

I made one before and it failed because I stupidly used about 300 turns. I am not sure if I got it right as i did not start - tail / tail - start / start - tail / tail - start/ etc the coils ? QUESTION is why are the coils connected start - tail / tail - start / start - tail / tail - start/ etc AND is it that either the magnets or coils are reversed every other one or BOTH coils and magnets are reversed every other one?)

Sorry this probably sounds so simple and I'm not getting it.

There are 80 magnets in a 12" disk brake drum (on each one of the disks) (the coils are stationary in the center, and the magnets magnets move)

Its designed to move very slowly and still output over 13 volts. It only will output the small weight of the water volume.

An axle is seated on two sides of a square box in a bearing and the disks are bolted to the axle. The divider of the square box holds the coils. This is clever because it allows for adjustment of all the tollerances and is strong. The square box also provides the housing of the unit from weather, insect nests, or dirt/debris. The brake drums are brought down close to the coils by means of adjusting the bolts that hold the brake drums to axle. (The axle itself is a long screw/bolt).

Im almost getting it and after all this work I feel its going to work great and be a nice 24/7 efficient use of many thousands of gallons of water falling three feet. The wheels will catch and hold the water as it falls.

I've really spent a lot of time and got ice issues solved and other issues solved and its almost a finished device, Just don't want to goof it up again because I don't get some fundamental principle of electricity right.

Thanks again for your help, its helping and you guys are understanding me.

Its a simple device made of plywood and epoxy. I have never heard of or seen this configuration of rotors/housing and hope to post a picture for the collection. Probably you can get a picture of it as its very simple. It is also less maintenance being simple.

By the way I just got 1000 nice 6 inch polycrystalline cells on ebay - so its kind of like "why do i need that 1 amp water wheel"? Well, because its so close to being a nice piece of craftsmanship probably that I want to see through after all the effort so far. And the relaxing sound of it quaintly  going pppsh -  pppsh -  pppsh over there in the background.

 

[electrondady1]

byan, that sounds totally whack!
your mags are round ?
30mm in dia.?
and only 3mm thick?

some times you say break drums and some times you say disks
if you have two brake rotors as in disk brake rotors will put 40 magnets on each disk?
so are you planing to stack these 3mm mags up to make them thicker?

[bryan]

They are from a disk brake drum, auto and they are mirrors (the same car) ones from the left wheel and ones from the right wheel. Yea there are 80 because a disk is 26cm diameter x 3.14 = 81.64)cm so there will be one magnet every 1cm. As the magnets are only 3mm a coil can be slightly less than a centimeter and have a hole 3mm in the center. There are 80 on each disk.

see attachment.

One leg of each coil can be over 2 magnets as the coil moves past the magnets but that is not what I understand causes the electrons to flow. I think I understand the electrons flow because of the field suddenly dropping away (as if the electrons are sucked rather than pushed)

My question is why or how to solder the coils togeather. Is having them reversed every other one create a bigger sine wave and thus more power? Or perhaps if the coils were all going in one way like batteries in a series it would result in a pulse dc effect?

The magnets are close enough to affect each others feilds but might also push or repel the field through the "slot" of the coil.

Got the idea to make the coils rectangles (like the magnets) thinking that the better portion of the coil will pass over the magnets.

Because there are two brake drum disks the magnets on either side will attract the field through the coil. (N to S)

I learned in the past that with a small flow of water if you want more power it slows down. If you have a little itty bitty generator the wheel will go faster - ether way your only going to get so much electrical energy as the water volume allows. Its a nice flow from a spring on a mountain but no pressure really like a garden hose on medium.

The idea with so many coils; is to add voltage so it will trickle into a 12 volt battery. So voltage is what im looking for as that tiny flow of water will only generate so many amps.  And it will generate 15v at a snails pace (not losing energy to gears or ratios) My guess is 30 rpm. Thats why Im not stacking the magnets or increasing the generating power as then the wheel will slow down "waiting" for more water to turn it faster... to make the voltage necessary to charge 12v.



ok thanks again

[Smithson]

Hi:      There is an equation for finding the number of turns for a single phase alternator in the back of Windpower Workshop.  Nturns equals 1200/combined surface area of magnets on one disk ( in sq meters)/ cut in rpm/ number of coils.  I don't  understand where the 1200 comes from.  Just before that he gives the example "suppose we want our alternator to begin to charge a 12 volt battery at 170 rpm. Say the alternator has 10 coils in series.  Nturns equals 1200/area of magnets/cut in rpm/ncoils.   1200/.047 (his example)/170 rpm (his cut in)/ 10 ( his coils), equals 15.  Your results would be different.

Are you trying to crowd the coils.  The center hole in a coil should be the same size as a magnet.  Also the coils should be reversed in direction.  Think about winding the coils in place because each solder joint will add resistance.   Arch

[electrondady1]

the photo helped
 you will need to clean up those rotors on a lathe or have them turned.
so there will be 80 poles on each rotor?

what will be  the spacing between mags on the inside dia. if you space one mag every cm

is this going to be a single phase machine or multi phase





 

[Flux]

Your basic assumptions are right in that your output will be limited by the power of the water wheel.

I think you are making hard work by using such tiny magnets. With an air gap alternator there is no loss before cut in so you could have used much bigger and convenient magnets to do the same job and got a much more efficient alternator and where the input is tiny any gain in efficiency would help a lot.

Anyway you have the magnets and it looks as though the spacing on your discs will work. The major snag is the thinness of the magnets and the need for very precise and concentric mounting of the discs and maintaining a very tiny gap between magnets and coils.I would make the coils 3mm thick and aim to get them in a stator about 4mm thick. With a bit of luck you may be able to get that to run in a gap of 6mm between magnets.

It will drive you crazy winding 80 coils and if you do that you need to reverse alternate coils. There is an option to leave out alternate coils and use 40 and wind them wider, in that case you don't reverse alternate ones.

There may be a case for doing the thing as a wave winding and wind one coil around correctly placed nails. Look at ed Lenz web site ( Windstuff now) for some ideas on this.

It could also be done as a skein winding where you wind a big loop coil and weave it in and out of slots to get the same effect but that method needs a bit if skill to get the initial loop right.

With such tiny magnets I really doubt that you can make much of a guess about the gap flux so it will be a test winding to find the number of turns. I think those tiny magnets will force you to use thin wire, this combined with low speed will leave you with a lot of resistance and not much output but it may be ok for this job.

Flux

[fabricator]

Man, why hamstring yourself right off the bat with those magnets? Why not get everything you can out of your resource? Get yourself some decent sized magnets and make life a lot easier on yourself.

[Frank S]

I was thinking he might place 4 magnets side by side then stack them 2 or 3 high to make a larger block of magnets. I think I read somewhere that the flux would not be direct accumulative but would for sure have a much higher T factor than singles also would mean less coils to make and they could be thicker.
  I don't know if he would have a high enough water flow for that setup.
  A member here  has made more than 1 stacked magnet rotors by using hard drive magnets  Odd shaped and stacked 3 high
 Just a thought

[electrondady1]

the thing is, even with those mags, if you spin the rotors fast enough and slipped an appropriate stator in place, it  might very well power buddy's house.

a 3mm stator is going to be a challenge.

i 'm wondering if those long skinny mags might be more effective if laid out at an angle /////////////  on the disk?

[bryan]

Thanks for help and  input! Ok it makes sense to me that the coil direction would be reversed  every other coil - because the magnets are reversed.

I can get the gap  down to 2mm because there are bolts that adjust the distance. I put some plastic sheet between the rotor and the coils to determine the gap and then remove the plastic sheet. If they scrape then I can back of a turn on the bolts.

I think I got I got it guys and I'll post the device pic when its done.

(I made one before and the problem was too many turns. With too many turns it would generate electricity but it was just "static" - as upon connecting an actual load there was nothing.)  So the mechanical details are known to work. It will use 2 liter pop bottles stuck on 1 inch pvc tubes as little "gravity levers".

So this should be a fun project.

We only use a smaller amount of electricity at night for Led light (sleeping anyway) so this water wheel will be for a solar system which isn't really depending on batteries. Mostly the batteries are used to stabilize the 18-20 volt daytime solar for laptops and such.