The Dynamics of a Dynamo
 

As I mentioned in an earlier post, I'm refurbishing a simple, Holland bike for a friend. I have one thing left to do to finish: replace the front light.

I bought her a new front light that is designed to work with a dynamo. The old one was a weak light and made to mount at the top of the handle bars, which was obstructed by her weave basket. So I bought her a small light, a Buchel LED 30 Lux (Secu Evolution) front light.

I attached the new light to the bike, and connected the black/white wire to the dynamo contact, per the instructions on the box. When I spin the wheel rapidly, the light doesn't light. The old rear one lights easily with this dynamo and the old front one worked with it, although it was not very bright.

http://bikeforums.net/attachment.php...hmentid=397931

Do I have the wrong kind of dynamo? The box says that it's "also suitable for hub dynamo". I assume that means it will work on other types. Have I connected it wrong? There are two wires. I tried connecting each wire to the dynamo. No combination works. Should one be connected to the dynamo and the other one somewhere else?

There's an on/off button on top of the light. I pressed it once and spun the wheel, thinking maybe it's just off. I then pressed and spun again. It has no effect. I can't imagine the LED inside are bad. Am I doing something wrong, or is this an incompatibility problem? If I need a different dynamo, what kind do I need?

Thanks in advance for any help y'all can give me. I'm desperate to finish this project and return the bike to my friend tomorrow.

-Russell

If the rear light works, but the front doesn't, the problem isn't the dynamo but rather the circuit. Make sure the live wire connecting the dynamo to the front light is intact and functional, and that the ground (often through the frame, but possibly a separate wire) is similarly functional. Finally, make sure the bulb itself isn't the problem.

You need to hook up the (+) wire to the dynamo and the (-) wire somewhere on the frame of the bike . Make sure the button is turn on as you spin the wheel and the light should turn on .

Show us more detailed pictures of where wires begin and end.

Yes, it looks like there are two wires coming out of the light, but only one from the dynamo. You need two wires to complete a circuit. Since it says you can use it with a SA hub dynamo (AC voltage, 3W), it will work with the bottle dynamo just fine (also AC, 3W). So I believe you need to connect the wire with the stripe to the dynamo and the other wire to the bike frame, which is the return path for the dynamo. The two little extra wires are for the taillight, and should be isolated from each other and everything else with some electrical tape.

And yes, you need to spin the wheel a bit to get the capacitor charged up before the light switch will work.

Switched lights are good with a hub dynamo ..

a bottle dynamo , because you can lift the drive drum from the tire , dont need the switch.



a S-A drum brake Dynamo combo hub would be a great front wheel for a utility transportation bike ..

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some older Bottle dynamos were DC , which had more drag and were from an era when the lights had filament bulbs in them.
+ lead went to each bulb -- was the ground through the Frame itself.