# (Q) How to make a regulator/rectifier for automotive use?

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#### dirtydoogle

##### New Member
I have a dead reg/rec on one of my bikes and am thinking about building a new one.
Has anybody done this before?
To my knowledge the input to the reg/rec is 45V AC and is three phase, the output will ideally be 14.2-14.6V DC.
I have been reading about shunt resistors and bridge rectifiers, but, I am not so up with the play these days.

#### MikeMl

##### Well-Known Member
The alternator uses a permanent magnet field, so the output is always max for any given rpm. Unlike with an automotive alternator, there is no way to modulate the field excitation; it is always full on.

The commercial regulators are a six-diode bridge rectifier to convert the three phase to dc, followed by a shunt regulator (wastes current by shunting it to ground). You can make it easier for the regulator by using the headlight as part of the current wasting circuit. (Headlight brightness is proportional to how much current needs to be wasted...)

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#### KeepItSimpleStupid

##### Well-Known Member
The rotor is magnetized my the battery voltage. It's usually chopped.

Auto generators had a permanent magnetic field.

AC portable generators witout batteries act a bit differently. Residual magnatism kick starts the process.

#### Mr RB

##### Well-Known Member
The rotor is magnetized my the battery voltage. It's usually chopped.
...

Maybe in the 1970's.

Modern bikes almost universally use permanent magnet rotor and 3 phase or single phase stator.

The "Honda 6-wire regulator" usually has 3 AC input wires, Gnd, Bat+ and Ign+. It differs from a typical 5wire Japanese regulator in that it has the Ign+ wire, which means the regulator does not drain battery power when the Ign is turned off.

Typical 5 wire regulators have 3 AC input wires, Gnd and Bat+ wires and they draw a few mA from the battery at all times.

Just buy a cheap replacement regulator and connect the wires.

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