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How to make led lighting on your bike with a rechargeable battery? Answered

hi,

I want to build led lighting on my bike with a 9V battery that charges all the time.
so i made a diode bridge and added some capacitors,
and i measured about 45V DC when i cycled down a hill.
thats way too much current to handle for a 9 volt battery,
so i got myself a LM317T, but at this point I'm getting a noob.
i get confused when i see ground and the - pole.
and i haven't worked allot with transistors,

so can someone build a circuit for me where i have;
- The diode bridge
- The 35V 560uF capacitor
- 1 Bright white led up front
- 3 Bright Red led's at the back

Thank you!

Tags:LedBike

5 Replies

user
steveastrouk (author)2012-12-04

Did you measure 45 v with nothing connected ?

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user
ingkiller (author)steveastrouk2012-12-05

jeah, just the diode bridge and the capacitors.

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user
steveastrouk (author)ingkiller2012-12-05

Ah, then you haven't really got 45 volts there, thats the open circuit voltage. Put a light bulb in circuit, and measure the volts across that when you're peddalling and you'll get a different number - a MUCH smaller number....

What LEDs are you using, and what forward current will they take ?

Steve

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ingkiller (author)steveastrouk2012-12-05

im not really sure about the front one,
but i think its just a bright white led, 5 mm 80 degrees,
and for the back i got 3 bright red leds, 5 mm 120 degrees
and i think they take about 20 mA

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user
steveastrouk (author)ingkiller2012-12-05

Reds usually take about 2V to light, so try a 22 Ohm resistor as a representative load.

What you REALLY want to do is to pump the dynamo into a supercap, and then have a smart supply to drive the LEDs.

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