Depends what alternator you have.
In an automotive type alternator the "charge" lamp doubles as a resistor to
enable excitation current to be supplied to the field windings prior to the
alternator running fast enough to be self exciting.
To get enough current flowing for this purpose means that the lamp needs to
be about 2w (for 12v systems).
For the Rotax alternator with permanent magnet field, none of this is
needed. So a LED will do without any paralleling resistor. Series resistor
may be needed however, typically 600 ohms or thereabouts depending on
voltage.
DuncanMcFadyean
On Thursday, March 21, 2002 4:31 AM, TroyMaynor@aol.com
[SMTP:TroyMaynor@aol.com] wrote:
> Hi Gang,
> I have searched but can't find it in the archive. Someone mentioned the
12v
> 3w lamp that is the alternator warning lamp being changed to an LED and
that
> you had to add a resistor, I think, to make the regulator function
correctly.
> Does anyone know what will work for sure on this? I have some nice LEDs
that
> are 12 volt rated that I want to use. In fact I want to make a series of
5 or
> 6 warning LEDs on a little panel to operate at the correct intensity with
a
> 12 volt input to each. I am planning to use one for oil press./master on;
one
> for alternator; one for door ajar; one for engine monitor; and starter
> engaged. The alternator one is the one I was concerned about. Is this no
big
> deal to do? I am electronically challenged. Please help if you can.
> Best Regards,
>
> Troy Maynor
> N120EU Monowheel Classic
> troymaynor@aol.com
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