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Boost 150mV to 1.5V

Discussion in 'Electronic Projects Design/Ideas/Reviews' started by Nursyukriah Idris, Mar 24, 2016.

  1. JonSea

    JonSea Well-Known Member

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    If the speed of the motor (generator) is stepped up about 20x, the voltage will be up to the volt range and so workable power may be achieved. If the air conditioner is running anyway, there should be enough power for some light.
     
  2. audioguru

    audioguru Well-Known Member Most Helpful Member

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    They measured a whopping 4.5mW. The windmill RPM was only about 860 then it was rotating at only about 14.3 revs per second. The "generator" was a cheap little DC brushed high RPM motor.
    Just now I connected a cheap little DC brushed motor to an LED and spinned (spun?) it as fast as my fingers could. It did not light.
     
  3. JonSea

    JonSea Well-Known Member

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    650 rpm yielded 0.15 volts and you're surprised that you can't illuminate an LED by spinning the motor with your fingers????

    This kind of motor typically turns at 6000 rpm @ 3 volts. For an LED with Vf of 2.2v, you're going to need at least 4400 rpm.
     
  4. dave

    Dave New Member

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  5. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hello,

    Isnt that just harsh judgement? Not to mention rude at the very least.
    I ignored your rude reply in my thread and i am betting other people will start to ignore you too if you continue to act with such indiscretion. Maybe think a little before you reply.
     
  6. JonSea

    JonSea Well-Known Member

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    Can you honestly read through the posts here and believe the student doing this project is benefiting from most of them?

    The options given have been to use a meter instead of a light, an energy-harvesting circuit to flash an LED once every 6 weeks, etc, etc. Other posts have said the project is stupid, worthless, best replaced by solar cells....

    What learning possibilites are there?

    o A boost circuit won't boost energy, just voltage

    o A permanent magnet motor can be a generator, but it has to be operating around its design speed

    o The efficency at each step must be considered and maximized, and that efficiency can't be >=1.


    Her project wasn't to improve the existing turbine & generator, but without getting the generator voltage up to a usable level, she has no project. She can expand the project slightly, look smart and achieve success, or she can write a paragraph and a couple of equations showing the assigned task is impossible and fail.

    Sure, my comments may be harsh. But consider the student, for whom English is probably a second language, reading through 6 pages of forum posts trying to shift the important from the noise.

    If my comments have not been valuable to this thread, please ask the moderators to ban me.

    Im sorry MrAl, i don't recall making any harsh comments in a thread of yours. Please refresh my memory.
     
    Last edited: Mar 28, 2016
  7. spec

    spec Well-Known Member Most Helpful Member

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    **********************************************************************************************************************************************************************************************************************************************************************************************


    You are missing the point Nigel. If you look at the video you will see that the motor is spinning at quite a low speed but still manages to light a string of LEDs
    The OP has stated that she has no remit to use gears so all this talk about increasing the motor speed is just a waste of space plus the fact that from the data which I requested from the OP the turbine is rotating at a reasonable speed. If you also look at the mechanical design of the turbine/generator you will see that adding gearing would be difficult anyway. The fact of the matter is that a small two-volt 6,000 RPM motor is the worst possible choice. Even a 12V motor of the same type would have been better.

    The OP has stated, however, that she is considering changing the motor into a generator. As generators are not as freely available as motors, a motor with a decent output would probably do the job, as has already been stated.

    spec
     
    Last edited: Mar 29, 2016
  8. spec

    spec Well-Known Member Most Helpful Member

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    Hi JonSea,

    You imply in a very presumptuous and overbearing manner that the use of a meter and energy harvesting techniques are somehow frivolous but you give no technical justification.

    The meter approach is the only practical solutions posted so far without a change of generator (motor) that is. It gives an indication of the power being produced at any one time. It is also cheap and simple to implement. If you look at the schematic you will see that it is not just a meter, as you imply, it is a resisytive load. This means that varying power will be absorbed from the motor, rather than the constant power that an incandescent bulb fed from a boost converter or a LED fed with a constant current. The meter approach will thus give a far better indication of turbine/generator performance rather than the bang bang approach of a lamp.

    spec
     
  9. bountyhunter

    bountyhunter Well-Known Member

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    My wife's Nissan has one of those awful CVT transmissions with "infinitely variable" ratio to optimize RPM. Maybe it could work on a windmill to optimize power transfer.
     
  10. ChrisP58

    ChrisP58 Well-Known Member

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    Ok. So we've established that it is indeed a brushed motor and not a brushless one. But that the speed at which it's being driven is probably too slow to produce a useful output.

    I think the thing to do now is to do a little experimenting.

    Equipment needed:
    1) One DC motor identical to that which is in the turbine. We will call this the Generator.
    2) A second DC motor. It may be the same or different. If different it should be larger. We will call this the Motor
    3) A varaiable voltage DC power supply.
    4) A tachometer, or some method to measure RPM.
    5) A voltmeter.
    6) A variable resistance to use as a load. As a first order approximation, I would select something that could go from about 4 Ohms to ~25 Ohms in ~0.25 Ohm steps. A 25 Ohm rheostat should do that nicely. In the following procedure, increasing the loading means reducing the resistance so that the current increases.

    Setup:
    1) Mount the motor and generator with their shafts coupled together.
    2) Connect something to the shafts that the tacometer can read.
    3) Connect the power supply to the motor. Set the output voltage to zero Volts to start.
    4) Connect the voltmeter and resistive load to the generator. Set the resistive load open, or to it's highest resistance.

    The purpose of this exercise is to find where the useful RPM operating range of the generator is. At each step you need to observe and record the behavior in both unloaded and variable loaded conditions. The amount loading will be determined empirically at each step to find where the useful power range is. To do so, you will adjust the resistive loading down while watching the voltage. As the resistance is lowered, the current increases, but the voltage will also decline. The voltage will be highest with no load. But, since that current is zero, the output power is also zero. You need to find the sweet spot where the Volts times the Amps results in the highest Watts. Enter a wide range of measurements into a spreadsheet program and graph of the results.

    1) Adjust the DC power supply so that the shafts are spinning at a rate equal to that of the turbine. Record the reading of the voltmeter and a range of loaded values.
    2) Increase the voltage to roughly double the RPM. Record the results.
    3) Continue until you reach the upper voltage limit of the motor.

    Your table will look something like this:
    Code (text):
                                 
       | DC motor | DC Motor | DC motor | --------  At light load  --------  |  ------  At medium load  -------  |  -------  At heavy load  -------  |
       |  Voltage |   Amps   |   Watts  |  RPM | Load ohms | Volts | Gen Pwr | RPM | Load ohms | Volts | Gen Pwr | RPM | Load ohms | Volts | Gen Pwr |
    01 |   0.5    |    0.2   |    0.1   |  650 |   25 ohms |  0.15 |  0.0009 | 620 |  15 ohms  |  0.13 |  0.0011 | 600 |  5 ohms   |  0.10 |  0.002  |
    02 |
    03 |                                                                                                                                              
    |
    |
    |
    etc.
     
    The values in the DC motor Watts column is calculated from Motor Volts x Motor Amps. Gen Pwr is calculated from Volts^2 / Ohms
    Data in line 01 is an example, and is not to be used in your table.

    Disclaimer:
    The procedure above is how I would go about determining the best speed change ratio for the gear/pulley requirement for your system, and is my first think through of a new process of which I don't have an existing history. Once in the process, I usually come up with variations as I see how things are going. Feel free to vary this process as you see fit at the time of testing.

    Have fun, and good luck.

    Chris
     
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  11. spec

    spec Well-Known Member Most Helpful Member

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    Hi Chris,

    Afraid gearing the motor is not an option for the OP, as previously stated, but your test-bed would be good for selecting an alternative motor with a decent output at the turbine RPM.

    spec
     
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  12. ChrisP58

    ChrisP58 Well-Known Member

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    Thanks Spec.

    If it shows how far off of the mark the existing combination is, then maybe she can get approval to make the change. At the very least, working through such an exercise will give her a lot better understanding of the issues that need to be considered for the replacement part.

    Chris
     
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  13. JonSea

    JonSea Well-Known Member

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    Spec, you are exactly right. A thousand pardons.

    Please explain to me how you're going to read a book in the dark by the light of a meter or an LED flashing for a microsecond every 6 weeks. I'm kind of slow on the uptake, so please explain in great detail.
     
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  14. spec

    spec Well-Known Member Most Helpful Member

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    Hi JonSea,

    No problems and thanks for the reply. :)

    To answer your question you will not be able to read a book in the dark by the light of the meter because there is no light output by definition. The thing is, to my knowledge, there is no requirement from the OP to do so. About the LED illumination every six weeks, I think you will find that that was a bit of fun by the poster. If you have a look at my post #47 you will be able to see that with a low voltage boost technique, and assuming a 40% power loss, there should be around 3mA available to light a small high efficiency LED, assuming a LED VF of 1.2V.

    By the way, although I think the meter approach is the best option for the reason already stated, it it only a suggestion which I have asked the OP to consider.

    Cheers

    spec
     
    Last edited: Mar 29, 2016
  15. JonSea

    JonSea Well-Known Member

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    The expeets have spoken.

    I am removing myself from this thread and will henceforth not be monitoring it. Please send me a message if anything is posted here.

    Nursyukriah, good luck with your project. I'm sorry people have strayed so far away from the central theme of your project. It's a good life lesson - those who talk loudest may have the least to contribute.

    - - - End of my participation - - -
     
  16. spec

    spec Well-Known Member Most Helpful Member

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    Hy JonSea,

    I, for one, would not like you to pull out of this thread; this is a difficult task and, to me, the more brains bearing on the matter the better. In general, I take the view that any proposal for a solution is worth considering and the more the merrier.

    Cheers

    spec
     
  17. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    In all honestly, several of AG's posts were not related to the actual question, and were going against the requirements specified by the OP. I expect this is what JonSea was referring to. That being said, the way he pointed it out was a bit rude. Let's try to be more polite here from now on.

    JonSea , Please don't leave the thread. You were providing some very useful information.
     
  18. JimB

    JimB Super Moderator Most Helpful Member

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    I agree.

    The main problem here is that the basic concept of the project (as I and others understand it) is fundamentally flawed and impossible.

    Here on ETO, several of us have tried to point out that impossibility, with limited success.
    Others have tried to provide a path for the OP to follow which would at least do something, even though that path may not be in the spirit of the project requirements.
    Others have made suggestions which are based on various misunderstandings and are just plain wrong.

    My current thinking is that:

    A/ The OP has nowhere to go with this project, it is impossible and that conclusion should be explained to the project supervisor as soon as possible. The cultural sensitivities (as I understand them) of the OPs location may also make that impossible.

    B/ This thread has gone as far as it can go with technical assistance.

    JimB
     
  19. MrAl

    MrAl Well-Known Member Most Helpful Member

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    Hi again,

    I did not read every single post here so thanks for pointing that out :)
    Interesting that this thread grew so long too.
     
  20. audioguru

    audioguru Well-Known Member Most Helpful Member

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    This thread is similar to another thread. My comments in this thread were similar to what I said in the other thread.
    In the other thread a person rode a bicycle at night and needed lights. A bike generator was tried but it produced too much drag making it hard to pedal so the person thought a windmill driving a generator would provide free electricity for the lights.
    A little computer fan was tried as the generator but it did not light the lights and the person did not understand why. I explained that the problem is that the weak little generator had a load that was much too heavy for it, try using it to light a dim little LED instead of the powerful incandescent lights. It worked but was not bright enough. I explained that a very large fan would probably do the job because it would work hard and produce a lot of drag like you pedalling and pulling an open umbrella behind you. Then I suggested using a powerful rechargeable battery instead like in this thread I suggested using a powerful solar panel instead.

    In the other thread there was no teacher wannabee rudely insulting and criticising me.
     
  21. DerStrom8

    DerStrom8 Super Moderator Most Helpful Member

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    AG, the criticism was for making comments that were not applicable to this thread. As I mentioned, the comments did not need to be rude, but the criticism was legitimate. You were taking the thread off-topic by offering suggestions that had little to do with the topic at hand.

    Please keep to the topic presented by the OP.
     
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