Voltage regulator for Vespa Primavera 1976

Hello everybody!
I have an old Vespa Primavera 125 (1976) and i would like to connect leds to the alimentation. My problem is that the voltage isn't regular, because it doesn't have a battery but it works with the motor. So i think i should build a voltage regulator but i don't know how. Someone can The voltage should be 6V, so i tried to connect a led with the resistor; it worked for a bit but then it burned. So i think i need a Voltage Resistor for higher voltage than 6 V.

This is the schematics of my Vespa

Thank you for the help and sorry for my bad english :wink:

Hmmm, automotive circuit diagrams not very readable I think... I presume this is a magneto model, so the power isn't
proper DC to start with? Googling "magneto regulator" showed a few promising links. Someone with specialist knowledge
out there? There is probably a way to upgrade to alternator/battery configuration (perhaps using existing magneto as
alternator? As I understand it a magneto is a combination of alternator and ignition points in one unit.

Yes i think it works with some kinda of dynamo.
Maybe with this is better: seigiorni.it
Sorry i really don't know nothing about motors :slight_smile: But thank you for the fast reply!

I think your main problem is that the output of the generator is AC not DC. Your LED probably failed because of excessive reverse voltage. You may not need a regulator, but you certainly need to feed your LEDs via a bridge rectifier as well as the usual series resistor or constant current circuit. As the voltage is so low to begin with, I suggest you make the bridge rectifier from Schottky diodes such as this one http://uk.farnell.com/on-semiconductor/1n5817g/diode-schottky-1a-95-10/dp/1458990.

Going by the second picture, your big round thingy with all the coils appears to be a combined ignition coil (the top coil) and two alternator stators (the bottom left and bottom right coils). The "condenser" (fancy name for high voltage capacitor), which works with the ignition coil, is sitting at the bottom between the two alternator stators. And then it looks like your points are jammed in there as well. A lot of stuff going on in there.

You'll want to splice into either line 4 or 5 for AC current; it shouldn't matter which because the AC waveform must be identical with either. If you're not using much amperage then dc42's suggestion of using four diodes would work, but personally I'd use a full rectifier in a GBPC case which would be easier to work with.

Plan B;-

Use diode to protect excessive reverse voltage.

Plan C;-

Use an other led to protect excessive reverse voltage, a pair led protect each other and double brightness.