On Fri, 27 Apr 2007 09:51:01 +1000, "marcus" put finger
to keyboard and composed:

Frank ~
Thanks for your offer of a circuit - can I take you up on that?

thanks

Marcus, in the rain!! (first time in about 3 months....)

This is the basic idea:
http://www.users.on.net/~fzabkar/alt-reg.JPG

If you have a grounded field alternator, then the field section of the
circuit needs to be modified. You also need to know the battery's
temperature coefficient before you can select your string of diodes.
Silicon diodes have a tempco of -2mV/degC, but zeners can have either
positive or negative tempcos that depend on the zener voltage. IIRC,
zener tempco is zero at around 5 or 6V. An alternative place to put
the signal diodes would be in the voltage divider.

I have added a momentary start switch just in case the residual
magnetism in the rotor is insufficient to self excite the alternator.
I have avoided using the "charge" lamp that normally provides this
function because the batteries would slowly discharge through it if
the motor were to stop.

One other thing you might like to consider is an overvoltage monitor
that trips a contactor if the regulator fails.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

On Apr 27, 8:33 pm, Franc Zabkar wrote:
On Fri, 27 Apr 2007 09:51:01 +1000, "marcus" put finger
to keyboard and composed:

Frank ~
Thanks for your offer of a circuit - can I take you up on that?

thanks

Marcus, in the rain!! (first time in about 3 months....)

This is the basic idea:http://www.users.on.net/~fzabkar/alt-reg.JPG

If you have a grounded field alternator, then the field section of the
circuit needs to be modified. You also need to know the battery's
temperature coefficient before you can select your string of diodes.
Silicon diodes have a tempco of -2mV/degC, but zeners can have either
positive or negative tempcos that depend on the zener voltage. IIRC,
zener tempco is zero at around 5 or 6V. An alternative place to put
the signal diodes would be in the voltage divider.

I have added a momentary start switch just in case the residual
magnetism in the rotor is insufficient to self excite the alternator.
I have avoided using the "charge" lamp that normally provides this
function because the batteries would slowly discharge through it if
the motor were to stop.

One other thing you might like to consider is an overvoltage monitor
that trips a contactor if the regulator fails.

- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.

http://homepage.sunrise.ch/mysunrise...ot/voltreg.htm