1/2 amp, 6 volts, 25 mph

[eljefino]

I belong to a motorized bicycle forum and there is a popular (cheap) 2-stroke motor they call the "happy time".

It has an onboard DC dynamo that outputs 5-7.5 volts, DC, but somewhat pulsy as the magnets on the crankshaft pass the pickup. 1/2 amp is available. Use more than that and the motor dies because it loses spark.

These bikes are good for 25 mph. I personally have a SLA 12v/ 7ah with 55 watt incandescent setup for commuting. But many city riders want a "be seen" light and of course even in daytime a running light would be super.

I was looking at the LED setups here b/c I want efficiency but am ready to admit when I'm over my head.

Bear in mind many but not all people who put a $200 motor on a $100 bike are the cheapest, albeit adequately creative, people you've ever met.

I'm looking to take back a solution that has no battery storage but maximizes light output without going above the 3 watt threshold or costing hundreds of $$$.

Have read many dynamo threads with interest but a lot of MBC'ers burn out dynamos going 25 mph all the time.

 

[schizeckinosy]

Hi,

For the ultimate "be seen" light, I use 4" truck led lights. THey are waterproof and incredibly visible. I use a yellow on the front, and red on the back, both set to "brake light" mode. I epoxied them on to reflector brackets for easy installation. They are 12v, so you will have to deal with the 6v-12v conversion with a DC-DC converter, which will smooth out the noisy power at the same time.

I bouught mine on ebay for $17 each. I need to get another one for my bike trailer soon, so if I find the seller again, I'll post his info.

Good luck! Dan

 

[n4zou]

Go to this link and look for the LED circuit that uses 2 power LED's.
http://pilom.com/BicycleElectronics/DynamoCircuits.htm
You don't need any capacitors shown, just the 4 bridge rectifier diodes and the 2 power LED's. Two Cree XR-E LED's will work just fine from DX.
http://www.dealextreme.com/details.dx/sku.2394
Connected in series they will provide almost exactly the 3-watt load required by that Chinese bicycle engine magneto. They designed that magneto to power a standard bicycle dynamo light set. Instead of hooking the lights to a dynamo with a wheel rubbing on the tire you simply connect them to the white magneto wire. If you use a dynamo lighting set make sure you connect both the headlight and taillight. Both load it at exactly 3-watts. If you only connect the headlight you only load it at 2.4-watts. This will allow the magneto or dynamo to produce more than 6 volts burning out the bulbs.