Re: 12 volt Bicycle Generator : discerning polarities for hooking up loads


"greenwanderer108" <greenwanderer108@xxxxxxxxx> wrote in message
news:JLmdnbkJ4b2uS8HeRVn_vQ@xxxxxxxxxxxxxxx
>I rigged them on my bike to test the actual output but can't get any real
> readings (400 milivolts max), let a lone enough power for even the
> smallest loads (i.e. 3volt toy motor). Either I got ripped off or I just
> am not hooking them up right. I think its the latter.
>
> At the bike shop, they had two different kinds available. I believe
> they're both made in Taiwan. One of them had only one terminal and that
> was rated 6 volts. The type that I bought (quantity = two) aparently are
> rated between 12 - 16 volts and have two terminals. One reads T and the
> other H. The salesguy explained it stands for Taillight and headlight. So
> they're made for lights.
>
> Anyways, since they are rated atleast 12 volts, I figured it would be
> sufficient to use for other applications such as a charger for the power
> pack in my electric bicylcle set up.
>
> I initially understood that generators are just like motors with the
> electromagnetism (two polarities) so how is it that the 6 volt generator
> can have only one terminal.
>
> And what about these two terminals for head and tail light. Obviously they
> aren't the equivlent of positive and negative leads, cause I can't get any
> power or readings from my digital multimeter (or anologue voltmeter) with
> the the leads hooked up to positive and negative . I remember the guy at
> the bike shop saying something about the both H and T leads being
> positive, and and that the negative lead of the light (or other load) must
> be grounded onto the generator. I tried, but still couldn't get any
> acurate
> power--or readings with the thing spinning as fast as I could get it.
>
> How do negative and positive polarities play in with such generators? What
> am I missing? If it's rated at 12 volts, why can't I get any more than
> 400
> milivolts. Do I have to ground the load some how or ??? I am lost.
>
> If it was like a motor with negative and positive leads, it would be so
> much easier . Can someone please help me out here? What if I want to
> combine the power of both of the generators in series or paralell?
>
> Thanks in advance
>
>
>
> This message was sent using the sci.electronics.basics web interface on
> www.Electronics-Related.com

Those bicycle generators are AC devices. Try switching your multimeter to AC
Volts position and see what you see. Unlike a toy DC motor they do not have
brushes or a commutator on rotating coils. They have fixed coils
surrounding a rotating magnet so they produce alternating current as first
the north pole then the south pole sweeps past the coil. And yes, the bike
frame is one leg of the circuit. May find that clamp that holds the dynamo
on the fork leg has a set screw that pierces the paintwork to make good
contact with metal of frame. The H and T terminals on one of your generators
may go to separate coils of different sizes so head has more power to it
than tail. Or they may both go to same coil and two terms is just for
convenience of hooking up. Try measuring resistance from each term to
generator case using your digital multimeter. Then measure resistance
between each terminal. If res between terms is just about zero they're
connected internally to top of same coil. If they're connected to two
separate coils the res will be the sum of term H to ground plus Term T to
ground.

Here's a link to just one page of some interesting reading.
http://www.nscl.msu.edu/~daniel/regulator.html

However, bicycle gens are low powered devices, rated at about three watts so
the likelihood of doing any significant battery charging with one is slim.

PH


.

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