8V AC out from a motor, power a lamp without killing motor?

Discussion in 'The Projects Forum' started by bryces, May 5, 2011.

  1. bryces

    Thread Starter New Member

    May 5, 2011
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    Hi,

    I'm new to this list - I hope this is the right place to ask something like this...

    I have a little petrol motor. A side effect of the coils that generate power for the motor is a seperate line out that carries up to 8volts AC. This line is earthed out by a kill switch to stop the motor.

    I have a very bright LED light (can run on AC or DC) that I would like to run off this 8 volt line.I've connected it up BUT the moment I turn the light on the motor dies - I guess because the power is going to earth through the light.

    Does anyone know if what I'm trying to do is possible? And what I have to do to make the light work and keep the motor running?

    Thanks,
    Bryce Stenberg.
     
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    3,789
    945
    The LED is obviously 'pulling' more current from the generator than it can supply. Try an LED with lower (less bright) current requirements.
     
  3. bryces

    Thread Starter New Member

    May 5, 2011
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    0
    Thanks Kermit2.
    Is the 'pulling more current' the only possible reason? I ask as motor manufacturer told me it can put out about 1 amp and the lamp draws less than 400mA (although I guess that 1 amp would be at full revs... maybe I need to run it up a bit harder, and get my meter across it and see what is really going on).
    Cheers, Bryce.
     
  4. CDRIVE

    Senior Member

    Jul 1, 2008
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    Do you have a limiting resistor in series with the LED? Also, what (AC) LED do you have? I know of no AC LEDs.
     
  5. bryces

    Thread Starter New Member

    May 5, 2011
    7
    0
    Hi cdrive,

    The led light is actually for a bicycle - is a Busch & Muller single led lamp that works whether supplied with AC or DC (don't know what electronics are inside there, do know it has capacitors to give it 8 minutes of 'standlight' time when no power is supplied to it) - was originally meant to run off a dynamo on the tyre of bicycle.

    I have no limiting resistor. Would one potentially fix the problem? Does one of these shunt more power to the motor rather than my lamp? Please elaborate...

    Regards, Bryce S.
     
  6. CDRIVE

    Senior Member

    Jul 1, 2008
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    No, what you have is a module. It probably contains a rectifier and a current limiter. To supply light for 8 minutes it probably also contains a super cap and that's what's loading your motor generator.
     
  7. bryces

    Thread Starter New Member

    May 5, 2011
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    0
    Thanks cdrive,

    I'll see if I can find a way to pre-charge my 'module' before letting it draw from the motor (a small battery might do it).

    Cheers, Bryce S.
     
  8. bryces

    Thread Starter New Member

    May 5, 2011
    7
    0
    Hello again,

    Thanks for the help so far, I see now that my light module draws too much current when first turned on.

    However, another thought occurs to me overnight but I don't have the knowledge....

    ** Is there something I can put in this 8 volt line which has the effect of limiting or restricting the flow of current to the light module?

    This line does not have to stay at 8 volts, when measured, depending on engine revs it is anywhere from 3 volts up to 8 volts. I just need to allow the capacitor in the light module to trickle charge. Or I could possibly even convert it to DC if that makes this doable (prefer not to though).
     
  9. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Please post the link to the product. I took a peek but there's quite a few Busch & Muller models.
     
  10. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    I found this link and this very funny legal notice. They could use spell check though!:D
    http://www.peterwhitecycles.com/b&m.asp


    Excruciatingly (Nauseatingly?) Important Legal Notice!
    The Ride&Charge is exclusively for use with the Ixon and Ixon IQ, not for any other light or device, and only for NiMH AA batteries located inside said Ixon, not for any other batteries, whether located inside said Ixon or outside said Ixon, and only for 6 volt dynamos, and not for any other power source, such as batteries, solar panels, newcueler reacterrrs, or whatnot. Whether or not some other company is making or thinking of making or used to make or thought about making or having had made by others on behalf of said maker or makers some sort of device that's in some sort of way somewhat similar to or perhaps different from the Ride&Charge,,,,,,(deep breath) I dunno. ;-)
    In other words, if you are wondering whether or not you can use the Ride & Charge with some other combination of lights and power sources, the answer is, I have no idea. If you try it, and it blows up with the force of a twenty megaton newcueler bomb, don't blame me.​
     
  11. bryces

    Thread Starter New Member

    May 5, 2011
    7
    0
    the link is http://www.bumm.de/produkte/dynamo-scheinwerfer/lumotec-iq-cyo.html - my lamp is the lumotec IQ Cyo senso plus.

    But I'm not sure if it will help as their english translation button for the site looks like it no longer works... Sprechen Sie Deutsch? :)

    I take it limiting the current is harder than just throwing a dirty big resister in the path? (as you can see I have very little electical know how).

    Thanks, Bryce.
     
  12. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Reading back over your posts begs the following questions...

    Have you tried to power this light from another source?

    Have you actually seen it work?
     
  13. bertus

    Administrator

    Apr 5, 2008
    15,648
    2,346
    Hello,

    Did you read this note in the mounting desciption:

    I have attached the complete PDF.

    Bertus
     
  14. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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    I forgot to answer this. If the generator can't keep up with the demands of the load I don't think limiting the current will cure anything.

    BTW, I fed that page into a language translator but the English version didn't provide me with any technical info worth a hoot.
     
  15. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
    99
    Ah, it even has some English! BTW, the use of the term "Earth", in its description, could rekindle the whole "What Is Ground" topic. If it hasn't been beaten to death yet. :D
     
  16. bryces

    Thread Starter New Member

    May 5, 2011
    7
    0
    OK, thanks everyone. The light does work when on a bicycle with a dynamo. I'll pursue an alternate source to power. With that in mind, if I turn the power to DC and put in a small lead-acid battery to be charged by this motor, do you think I'll suffer the same fate of drawing to much current keeping the battery charged?

    Cheers, Bryce.
     
  17. CDRIVE

    Senior Member

    Jul 1, 2008
    2,223
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    So you're saying that if you peddle for a short while it will eventually come on? Not surprised.
     
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