BMW R Regulator.pdf

BMW R Series Motorcycle Regulator Schematic

PARTS:

R1 330

R2 270

R3 470

R4 1.5K

R5 1.2K

R6 100

P 100 ohm pot

C1, C2, C3 100nF ceramic

Q1,Q2 BC327

Q3 BD244A

D1 1N4148

D2 BZX6V2 zener, 6.2V

D3 1N4003

D4 no markings, but a 10A, 50V schottky should do the job here. Strangely enough, the diodes in my

Siemens databooks that use this package go up to about 3A, which I consider a little low for this application

(BY245, BY246).

From the wiring diagram in my manual:

D+

Goes to output of diode board and alternator telltale.

Goes to one end of alternator rotor.

Goes to the other end of the alternator rotor, and it may also go to bike ground through the case of the

regulator.

Description:

Correctly adjusted, the voltage on the pot wiper is slightly less than half D+ (appx. 0.47*D+) and Q1 will

conduct if (D+)-(Vp)>6.2+0.7+0.7, or 0.53*(D+) > 7.6V, (D+) > 14.3V. If D+ is lower than 13.7V, Q1 will

not conduct, Q2 will get driven via R5, and Q3 will conduct. Df will carry a voltage. When D+ rises, Q1 will

start conducting, Q2 will get pinched gradually, and so will Q3. Voltage on Df will drop.

This was originally investigated by Matt Bennett , but the diagram, functional description, and many

corrections were done by Rik Steenwinkel, rsteenw@ibm.net or rik@apd.dec.com.

Revised on 10/3/95 by Matt Bennett