DIYbanter - View Single Post - Abate Holding Your Breath...Thompson's Design

John Larkin

On Wed, 18 Jan 2012 06:43:25 GMT, (Nico Coesel)
wrote:

John Larkin wrote:

On Tue, 17 Jan 2012 11:27:31 -0700, Jim Thompson
wrote:

On Tue, 17 Jan 2012 10:18:10 -0800, John Larkin
wrote:

[snip]

A uP would be good for sophisticated algorithms, like minimizing the
subjective effects of alternator drag.

John

So NOW it has drag?

...Jim Thompson

Conservation of Energy. Since a leisurely pedal down to the pub might
take, say, 20 watts of leg power, a few watts of charger kicking on
and off might be noticable and annoying. People already complain about
hub generator vibration. A commercial product would get bad reviews if
it annoyed the rider with erratic loading, so a $1 ARM with ADCs and
PWMs and algorithms would be appropriate to control it smoothly. But

Using a controller makes a lot of sense. I'm thinking about a PFC
scheme (about 25V into a big cap) and a forward converter-ish output
to drive a big LED. IMHO a battery is a bad idea. Better use a big
capacitor.

It does make sense to ride the high end of the load curve, namely
rectify the alternator output to a high voltage and then switch down.
That's the opposite from the "nearly shorted/constant-current" place
they usually work. The switcher will have to work from, roughly, 10 to
100 volts input, maybe more. I'm thinking the downhill run from the
Rainbow Bridge to Lake Donner...

John