Bicycle Mechanics - Testing dynamo headlight without hub?
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I'm in the process of building a dynamo wheel, except that the hub has not gotten to me yet and will not for a few more weeks. I've already received the headlight and would like to make sure it works, in case I need to exchange it or something. What would be the best way to go about this? The light is a B&M Lumotec IQ Fly.
01-06-09, 03:37 PM
I would expect that a small 6 volt transformer would do the job for you. Do NOT hook up backwards (115V into 6.V side)! Should be available at Radio Shack or any electronics store for a few bucks. Hub dynamos put out AC so a battery pack might damage something.
I just ordered a Lumotec for my generator hub bike. Now waiting for the light.
I would just connect it to a 6V battery setup out of 4 1.5V AA batteries or 5 1.2 V rechargeable batteries. I do not know about IQ Fly specifically, but typical dynamo lights work no matter whether you drive them with AC or DC. On the other hand, I would refrain from hooking it up to an AC transformer that provides unregulated voltage. For a low-power transformer, you will depress the voltage below the nominal. If you do not, for a higher-power transformer, then you can damage the lamp. If you were to insist, though, on a transformer, I would use a railway model transformer for which you can vary the output, until the lamp is bright enough.
01-06-09, 05:31 PM
If it is Incandescent, It will be happy as long as it has the right voltage. Led's are a different story, They have positive and negative leads on them. (a quick google search reveals that it is an LED source)
LEDS are operated on DC current, and from reading the previous posts, a dynamo hub provides AC. This leads me to conclude that the LEDs are powered by some form of Diode rectifier circuity inside. And diodes rectifiers are designed to handle current for both of the leads. My educated guess is that you would be fine running a 6 volt Source through the leads. I wouldn't leave it attached too long, Maybe 1 or 2 seconds. If it doesn't work in that amount of time, it won't work longer.
(DISCLAIMER: IF YOU FEEL UNSAFE WITH ANYTHING THAT I SUGGESTED, DON'T DO IT!! ALSO, I PROVIDE NO WARRANTY, EXPRESSED OR IMPLIED WITH MY ADVICE.)
sorry for the lawyer talk, but based on my knowledge of electric circuits, I am confident that your gear won't be harmed.
A regulated power supply might be your best option for bench testing. Look for 6v, 500mA.
Otherwise, a variable bench test regulated power supply should let you set the same settings.
Using a battery could overcurrent the light.
Thanks for the info everyone. I wasn't expecting much of a response! Definitely don't want to break the light, but I will carefully try to test it after some more googling about... electricity.
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