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8 small 3-volt hobby motor/generator harvesting

  1. Nov 16, 2016 #1
    How difficult would it be to harvest the electrical out put of 8 small 3 volt motor/generator?
     
  2. jcsd
  3. Nov 16, 2016 #2

    russ_watters

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    Pretty easy.
     
  4. Jan 2, 2017 #3
    can you direct me to an example?
     
  5. Jan 2, 2017 #4

    russ_watters

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    Not really, no. Your question was really, really vague. If forced to take a stab at it, I'd say connect a string of 3V light bulbs to it. But I'm going to guess that's not what you are after...

    In order for us to help you, you are going to need to explain what it is you are actually trying to do.
     
  6. Jan 2, 2017 #5
    Sorry for the vague question. I would like to charge 4 AA batteries using the wind to turn a turbine that rotates a large plate that then rotates the 8 separate 3v motor/generator. Ive built a prototype and am not sure how to insure that each output from each motor can be stored and utilized for recharging batteries. Rpm is 72 to 1, the motor / generator out put is 6VDC,6000RPM,90mA Rated 4600RPM Maximum, 137g-cm,620 mA Starting Current: 2.8A .
     
  7. Jan 2, 2017 #6

    russ_watters

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    Makes sense now. You need a charge controller to deal with the fact that the turbine's output is inconsistent in order to effectively/efficiently charge the batteries and prevent over-charging.
    http://www.windbluepower.com/articles.asp?ID=127
     
  8. Jan 12, 2017 #7
    Thanks for the link. I was hoping to combine the solar and motor/generator output through a solar charge controller, the link indicates there's a problem with that, most likely i will need 2 separate controllers. thanks again
     
  9. Jan 14, 2017 #8

    sophiecentaur

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    Before you spend more time on this project, you should see how the motor behaves when connected to the actual turbine. If you are getting 90mA at 6000rpm then how will you achieve that speed with a wind turbine at only a few hundred RPM? If you are considering using gears to give you more RPM then you will have efficiency to deal with. Commercial Wind Turbines tend to use purpose built alternators and they work fairly well )but seldom very impressively - I speak from experience of a small (commercial) 12V wind turbine on a boat, which was nicely engineered and used a specially designed multipole alternator.
    You can have fun with this project but it is as well to start with realistic estimates of what you expect. The turbine is the crucial part of your project (and the siting vs wind supply)
     
  10. Jan 14, 2017 #9
    My goal is to be able to charge 4 AA 1.2 volt 2500mAh rechargeable batteries; through out the day in order to use the batteries for up to 4 to 5 hours a night. I'm looking to see if i can satisfy the bare minimum requirements for charging small devices and or powering enough LED's to light a small hut. Once one set (4) of batteries is charged another set can begin recharging during the night utilizing the wind of course. Currently my prototypes is only engaging 2 to 3 gens per revolution and only intermittently through out the revolution, my drive plate is off by maybe a few 1000's of a millimeter. Revs are no where near there optimal of 4800 revs, but my meter indicates voltages of 3 to 20 volts. Since this is just a looky looky i'm using pressure to engage the gens from the drive plate, the drive plate i initially designed has 720 teeth, but of course before i go there i want to see how it all comes together. I have looked for systems that can combine wind and solar and are mobile and compact enough for an apartment dweller to utilize and i have found none. After super storm sandy hit my area i began looking for a charging system that was green enough it would not endanger my family and home to use. Thanks again for your response and thoughts and your help is greatly appreciated.
     
  11. Jan 14, 2017 #10

    sophiecentaur

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    So this is a gearing system. Have you measured the energy loss from your high ratio up-gearing?
    What does this
    "Currently my prototypes is only engaging 2 to 3 gens per revolution and only intermittently through out the revolution,"
    mean? Is your coupling actually slipping? If you are going for a regulation system then electronic regulation could be the best bet.

    I don't want to be just a 'wet blanket' here but we do get frequent questions about systems like the one you are proposing and I cannot remember anyone posting, subsequently, that their system has been a great success. What you are after is a very sophisticated EE design and, for a start, it is unlikely that a motor can work very well ' the other way round'. If you really want a system that does a proper engineering job and not just a fun project then it has to be properly engineered from A to Z. You would be best to look at what's available on the market and bite the bullet; it cannot be done on a shoestring. Hundreds of GBPs or USDs are involved for the lowest spec system. Serious Energy will require serious Money. Sorry.
    Look on eBay for good value but read the small print in the ads and question the supplier closely about what they actually claim about their equipment.
     
  12. Jan 15, 2017 #11
    Have I "measured the energy loss from your ratio up-gearing"?. I guess you mean, have I taken in to consideration the back emf, weight of drive components such as turbine, drive plate, moment of inertia, angular momentum etc. yes. The drive plate is imperfect and unbalanced. So my first run only engaged 2 or 3 gens and for only 2/3 of one rotation of the drive plate. The drive plate is sitting in for the 720 teeth gear wheel. The motor gens are driven by a ten teeth pinion gear, giving the setup a 72 - 1 ratio. My current wind tunnel is a leaf blower and a cheap anemometer. Engagement of the motor/gens by the drive plate is through direct pressure which adds another level of difficulties, but less expensive than having the 720 teeth gear made up. Kind of sad to see so many unanswered post or no follow up to those post and so many are years old. I understand this endeavor is to some extent considered a huge and expensive undertaking. Honestly I did not consider the difficulties before I began. After getting to the prototype stage, proof of concept stage, I still don't. Whenever possible (and you won't know till you try) any new idea, concept should be done on a shoestring; once understood in a real world context and I'm not saying don't do the math but also have something you can touch and play with. I'm not sure what you mean by GBP or USD. Thanks for your thoughts on the matter it's greatly appreciated.
     
  13. Jan 15, 2017 #12

    sophiecentaur

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    GBP - Great British Pounds
    USD - US Dollars
    That's a pretty high ratio and I don't understand about the output pinions only engaging the drive wheel for part of the time. If you want gears to be efficient then I though the profiles had to be just right and, of course, they would need to be meshed correctly all the time. A friction take off is really not very efficient. Cycle Dynamos with a wheel resting on the tyre are pretty poor, compared with the 'Dynohub' style, in which there is a magnet that rotates with the hub and q stator coil. No mechanical linkage at all - just magnetic coupling ( as with my wind turbine)
    That's your opinion but it's not supported by most successful Engineers. I must admit that I never embark on anything that I can't be fairly sure will work properly. 'Suck it and see' gives such a divergent path in any investigative process that you can easily get nowhere at all because of some very minor matter. Loads of diagrams and calculations (plus loads of reading) can deliver a more credible design than just bolting a few things together. But that can be great fun, I admit.
     
  14. Jan 16, 2017 #13
    Yes it is.
     
  15. Jan 16, 2017 #14

    sophiecentaur

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    Just consider this. Commercial electricity generation is always done with Alternators. Why is that? It's because brushes are incredibly inefficient. Where possible, they now use brushless DC motors, for the same reason. Motor cars switched to Alternators in the 50's. Unfortunately, a car alternator is probably too big and clunky for use with a small wind turbine and it probably would need some help with gearing to get the rotation speed high enough to make up for the low number of poles.
    I actually think that you would probably be better to try to build your own multipole alternator, with a pancake shape. You could use some of those incredibly powerful magnets that are starting to be cheap as chips. Brush and friction losses would be hugely reduced and the initial start up torque would be less too (light winds are devils for small wing turbines). Apart from the problem of getting clearances between rotor and stator, as small as possible you wouldn't even need the coils to be particularly uniformly wound. You are obviously prepared to put in significant effort in your projects so why not give it a go? (An internet search could give you construction ideas)
     
  16. Jan 16, 2017 #15
    Before I began I set up certain milestones and rules, one of which was that the first generation had to be made with off the shelf items. Hence the small 3 volt hobby motors off the shelf charge controllers and sweat. Small solar panel etc. I have many neodymium magnets and the hematoma to prove it. A crew out in California recently announced the ability to print specifically shaped magnetic fields. Like I said before shoestring budget. In the last 4 years I have built a magnetic motor based on a ww1 aircraft motor, a spring motor, a big motor running 8 small motors, piezo electric generator. Took a couple of month off to win an award for abstract art from a local gallery, the piezo one set me off I needed a break arts my first love. I use a free 3D program for all the part modeling. I have considered your multipolar alternator idea before. I'm trying to keep an eye open towards commercial viability hence the need to stay away from reinventing the wheel. I do love the magnetic coupling thing since I need this thing to be waterproof and designing for particular waterproof tolerances will only up the cost. Thanks
     
  17. Jan 16, 2017 #16

    sophiecentaur

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    The whole thing can be fitted into a waterproof shallow sealed drum and the only place where a moving seal would be needed would be on the central shaft bearings. No problem and this is the same for your present design with the plate. Is it supported at both ends of the shaft or is it just cantilevered?
    This link shows how mine was made and could give you some ideas about a design. You would need to have an alternative to the bespoke magnetic rotor, though.
    I must say, it was not good in light winds.
     
    Last edited: Jan 17, 2017
  18. Jan 16, 2017 #17
    The current prototype shaft is supported at both ends. Using the mag coupling would make it cantilevered, correct? Sorry but your link is not showing.
     
  19. Jan 16, 2017 #18

    sophiecentaur

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    I can sort that out tomorrow or you can search Rutland 503 wind turbine maintenance. There is a YouTube movie for bearing replacement.
    The 503 has two bearings. It's quite a demanding job as it is going 24 7 and it can be at high speed.
    Regulator needed to short output at high speeds
     
  20. Jan 17, 2017 #19

    sophiecentaur

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    Here is the link to the Rutland Disassembly. It shows the construction and, by making the whole thing more bulky, it could be a DIY project.
    I have to declare my interest (if it's not already glaringly obvious) in the demise of brush motors being used backwards. It is a thoroughly bad idea. Their only advantage is that you can get one out of a drawer!
     
  21. Jan 22, 2017 #20
    Thanks for the video. In my humble opinion a vertical type wind generator is best suited for a boat, maybe using an old ceiling fan as an alternator type base. My thing is charging batteries so sticking to D.C. Is best for me.
     
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