> -----Original Message-----
> From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] On
Behalf
> Of YES NOPE9
> Sent: 15 December 2010 17:58
> To: Microcontroller discussion list - Public.
> Subject: [EE] Replacing a failed small engine voltage regulator
>=20
> I have a CASE trencher (CT ) and the regulator
> failed.
> The CT has a 12V battery to start the engine.
> There are two leads coming from the flywheel.
> I believe they are attached to a coil that is
> activated by a passing permanent magnet. I have
> connected a full wave diode bridge to the leads and
> put a cap across it.  I measure 33VDC ( no load ).
>=20
> I put together a circuit where a resistor drives
> a 14V zener to ground. A 2N3055 transistor has it's
> base connected to the 14V.  The collector goes to the
> fullwave bridge.  The emitter goes to the battery.
> This circuit worked fine when I tested on the bench.
> The output at the emitter ( under load ) was 13.4 V.
> When I connected it to the CT , the zener burned up.
> I have not yet investigated what may have happened.
>=20
> I can think of many ways I might proceed.
> I would invite comments on whether I should stick with
> a linear regulator approach or do some sort of switching
> regulator ?
>=20
> ( Olin does not have to explain to me that I am a
> congenital idiot .... I concede the point  )

Most small engine charge regulators are of the shunt variety, usually
using an SCR.  A regulator/rectifer from a small motorbike or scooter
will do what you want and are cheap to buy.  Even a three phase one from
a bigger bike could be used if you just ignore one of the phase wires.

Regards

Mike

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