6 Vac to 6 Vdc rectifier /regulator for a motorcycle

Well, I'm half-way off the hook, if you consider the supplementary alternator/generator to be "another winding". ;-)

Thanks! Rich

A lot of the old bikes just used a selenium rectifier. They were quite big to handle the current

I bought a bridge rectifier to convert the ac to dc, but I can't figure out a circuit to control the voltage and amperage so that I wont boil the battery

build a rectifier / regulator for my motorcyle.

You are right there is a high voltage coil for the ignition system, but there are 2 other coils in the magneto for the 6 v loads one for the battery and one for the lights

inside the flywheel there are 3 coils, 1 supplies high AC voltage to the ignition system, 1 supplies 6V AC to the battery, 1 supplies 6V AC to the head lights. I have found some circuits, but I can't figure out the values of the components. I found a verry interresting one using a LM338 adjustable regulator, but I can't figure out the resitor and other components values to make it work as I need ?? As you say a big zenor diode to control the voltage, I agree but what is the value or specs of the zenor ??

They must have sold another model of the bike that had a battery. If they are still in business, maybe you can just buy a regulator from them. I wonder if they have separate coils for the battery and lights because the battery winding has enough resistance that you don't need a regulator. If the no load DC is less than about 10V, you could briefly connect the batter to it through an ammeter, and see how much current it is trying to source. A

Tam

Thanks for coming back with a little more information. If you could post a link to the circuit with the adjustable regulator maybe we could make some suggestions.

Back in the day, Lucas, Lord of Darkness, used a big zener for shunt regulation. I wouldn't do it that way now. An "active zener" circuit would perform better. You could make a simple one with a 6.2 or 6.8 volt zener, a power NPN transistor and a couple of resistors. I might be able to post an ASCII diagram when I have some time. Basically you put the zener in series with the transistor base. When battery voltage exceeds Vz + Vbe, the transistor turns on and its collector, which is connected to the battery positive, sinks current to ground through the emitter. You'd want to put a small resistor between the zener anode and the transistor base, and another resistor from the zener anode to ground, and by fiddling with the value of the latter you can trim the voltage setpoint somewhat. The cathode connects to battery positive, as is the zener cathode. That's it in a nutshell. Maybe use a Darlington to keep the base current down so you can use an ordinary low power zener.

There wont be enough current to boil teh battery, the output is just enough to charge battery and run lights.