Vespa Help

[Swallow]

hello everyone - i am working on a Led headlamp unit for my '64 Vespa. i will be using 6 seoul p4's in strings of three each with a buckpuck @1A. This will recieve power from my flywheel & stator which through a rectifier gives out 12v-14vDC.
I also want to run a pair of seoul p4 leds from the same power source at a lower current, say 700ma, but I am no good at working out how to drive them from a 12v+ source. I've used the buck puck/3 led arrangement before with a modded light for my mtb with 14.4v battery, but really that was based on advice from good cpf'ers rather than any knowledge of mine, so I'm looking for help again with suggestions for...

.....driving a pair of p4's @700ma or thereabouts from a supply that fluctuates from 12v to 14 and a bit....


Thanks in advance! Tom

 

[gillestugan]

You can use the same design as in your mtb light, using a 700mA buckpuck and two P4s in series.

You may also ask a moderator to get this thread moved to the transportation lighting forum.

 

[znomit]

McGizmo made an LED headlight for his LX (and I'm doing a taillight for mine).
http://dmcleish.com/CPF/Vespa/index.html

Check out The Rezistor too.

You can get adjustable buckpucks, a pot alters the current. Or you can buy ones fixed at 350, 500, 700mA.
http://www.ledsupply.com/buckpuck.php

 

[LukeA]

McGizmo made an LED headlight for his LX (and I'm doing a taillight for mine).
http://dmcleish.com/CPF/Vespa/index.html

That doesn't have a beam cutoff, and so is pretty dangerous.

 

[Swallow]

but if I were to run two p4's in series through a buckpuck at 12v or up to 14v would they not blow up??

I understand running three in series at that kind of voltage would give each one around about 4v but using only two leds would that not give each one 6v ie tooo much?

 

[znomit]

The buckpuck takes the bikes 12-14V(it varies a bit) and puts out the correct voltage and current for the LEDs. You need at least whatever the total voltage of the LEDs is plus 2V for the driver. It will work with 1 or 2 LEDs and probably 3 leds as long as their voltage isn't too high.
Thats the whole point of the buckpuck.

Datasheet:
http://www.leddynamics.com/LuxDrive/datasheets/3021-BuckPuck.pdf

 

[Swallow]

aha - i didnt know that the buckpuck regulated voltage as well as current...

 

[gillestugan]

It regulates the current by adjusting the voltage to the led until the correct current is achieved.