Regenerative braking model

Discussion in 'The Projects Forum' started by rattleraj2000, Jul 11, 2010.

  1. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    hi,
    i am trying to do a regenerative braking model. I am using a 12v permanent magnet dc motor. I ve coupled a freewheel to the motor shaft so that on braking(cutting of supply from motor by using a DPDT switch) the voltage generated by the motor gets collected onto the capacitor connected to the other terminal of the DPDT switch. It is working and showing constant rise in the capacitor charge. the capacitor charge stays for a very long time successfully since i have put a diode and a resistor in series with the motor terminal and the capacitor. I am now trying to use the charge of the capacitor to light up an led which i am not able to light since the voltage stored in the cpaciotr is very small about 1.5 volts and the led lights up on 2.5 volts. can anyone please suggest me a method in which i can amplify this capacitor voltage so as to light the led. presently i am thinking of using a dc-dc step up converter,but yet to test it.please help.
     
  2. eblc1388

    Senior Member

    Nov 28, 2008
    1,542
    102
    First, if you don't use an appropriate title for your question, then others might not even look at your post in the first place.

    For your problem, I would suggest you try it without the series resistor to reduce energy loss so that voltage on the capacitor can rise above 1.5V to enable you to light a LED. If that fails, try reducing the capacitance by half to get a higher terminal voltage.
     
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  3. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    Regenerative and recuperative Electrical energy system demonstrator:

    I apologise for the inconvienience regarding the title. I am a new user.
    Thank You for the suggestion. I will try it out. the capacitor used in my experiment is 2200uF.
    Will connecting a DC-DC step up converter be of any help. Since I got this DC multiplier circuit which boosts up the voltage from 0.7v - 3.3v. from the link http://www.reuk.co.uk/DC-Voltage-Multiplier-Circuit-Plans.htm.
     
  4. hgmjr

    Moderator

    Jan 28, 2005
    9,030
    214
    Greetings rattleraj2000,

    Don't worry about the title hiccup. I have edited it to more closely align with your topic. Hope you get the assistance you need.

    hgmjr
     
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  5. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    What kind of led do you have?
    You could take a look at a joule thief.

    Bertus
     
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  6. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    I am using a normal 2.5volts led. I am now having a look at the joule thief led.

    For switching purpose I am using a DPDT switch. does it use up most of the coltage which would have otherwise been used to charge the capacitor? On researching I saw that a power MOSFET was used and a PWM generator was provided to give the pulses for the switching of MOSFET. But i couldnt quite get the principle.

    please help.!!
     
  7. beenthere

    Retired Moderator

    Apr 20, 2004
    15,815
    282
    A schematic would help to see how things are arranged. To do regenerative braking, you must either store the kinetic energy or dissipate it as heat.
     
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  8. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    I am storing the energy in a capacitor of 2500 uF,16v. How do i upload a schematic which i made it in paint ?? please suggest. I am trying to upload the schematic i made
     
  9. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,348
    Hello,

    Here is a part of the FAQ on posting aatachments:


    Bertus
     
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  10. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    I am attaching the schematic done by me just now. Apologise for the bad sketch as i did it just now just to upload.sorry for the inconvienience.
     
  11. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
    17
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    After giving an input nearly 2.5 volts I am swictching on the motor by a DPDT switch. the other end connected to the capcitor. On changing the DPDT switch the motor gets disconnected from the supply and due to the inertia it generates a voltage until it comes to a stop. this voltage generated gets stored in the capacitor.
     
  12. BMorse

    Senior Member

    Sep 26, 2009
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    what is the RPM rating on your PM DC motor??
     
  13. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
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    I am using a Scalextric car. I dont have the motor specifications for that, But as for thesearch in the net i got it as 12-15v motor at 18000rpm
     
  14. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234
    What is the maximum RPM's that you are running those motors at? The reason I ask, is because I wanted to try and figure out how much output you get from the motor when braking.... since those motors are rated for 18000 RPM's, they would have to be spinning that fast to generate close to 12 to 15 volts output, but since you are only able to charge the capacitor to around 1.5 volts, you must be running the motors at very low RPM's..... If you do not need the speed, then you could generate more power from lower RPM PM DC Motors, if you have to option anyway... Are the motors geared down at all, or are you running them directly off the motor shaft?? If you do have a gear reduction, what is the the gear ratio?

    Edit:
    I looked up the specs of the car so I have the answers to my questions.....

    B. Morse
     
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  15. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
    17
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    rite now I am using a simple 12v Permanent magnet dc motor. I don ve the specifications for them. Its a unilab product. I am not able to get the data sheet.I have coupled the motor with a free wheel so that it rotates more after the supply is cut off. but its not able to generate more than 1.5v. But it doesnt. I am runnin it on almost 5-6v. but the charge stored is very less. I am attaching the capacitor charge. Please find attachment. thank you

    Yeah. That is the one MABUCHI.. Thanks
     
  16. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
    17
    0
    I have not yet tried with the scalextric car. But I am going to use it since I want to demonstrate in a real time toy car showing enough regenerative energy captured to improve its own motor performance. is it possible??please help
     
  17. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    You will not get more power than that from the motor unless it is spinning at its maximum RPM's..... you will most likely have to come up with a way to light the LED off of that amount of power.... as suggested possibly a joule thief circuit will be sufficient to accomplish this >>>

    [​IMG]

    This circuit is enough to light bright LED off of 1.5 Volts.... I have used the same to light 9 white LED's off of 1 1.5 volt AAA battery.... see video here >> http://www.youtube.com/watch?v=6zVOcND-FuQ

    B. Morse
     
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  18. rattleraj2000

    Thread Starter New Member

    Jul 11, 2010
    17
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    Thanks for the help.

    Is it possible to light the led directly from the capacitor without a battery?? since charging takes a very long time for it.
    Is it even possible to run the motor at its high speed and use the energy to improve the effeciecny of the motor itself once the energy is recovered.?? Since i wanted to demonstrate to improve the motor effeciciency.
     
  19. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    Since the voltage from the motor freewheeling is a.c. (check this with an oscilloscope) try a voltage triper or voltage quadrupler. Look on Wikipedia. This ought to give you ~6V which can be reduced appropriately for the LED. If you use Schottky diodes in the doubler you will get even better output.
     
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  20. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    You should be able to light the LED right off of the capacitor using the joule thief circuit, but you may want to somehow keep the LED circuit disconnected while charging, or the circuit will just drain it as you are trying to charge the cap.

    I am not sure if there would be enough energy generated to be able to power the motor itself...

    B. Morse
     
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