"Jim Thompson" wrote in
message ...
On Fri, 26 Nov 2010 18:52:38 -0000, "Ian Field"
wrote:


"Jim Thompson" wrote
in
message news
On Thu, 25 Nov 2010 18:58:15 -0000, "Ian Field"
wrote:

Some parts of the AN170 PDF for the 555/556 timer are poor quality and
barely readable - it just so happens that the automotive regulator app
is
very blurred.

Also; I have my doubts about the design shown as it shunts the output
(can't
read the resistor value!) and takes its output from a 68 Ohm resistor
feeding the Vcc pin.

Does anyone have any automotive regulator apps for the 555?

The one in AN170 isn't a PWM as such - its just used as a window
comparator
with latch, at least its not a self oscillating PWM, it switches on the
field winding when the battery drops to the low threshold and off when
it
reaches the high thr.

Thanks.


While that circuit is pretty much like my original alternator
regulator chip (see my patents), that's NOT the way to make a good
regulator.

Go PWM. All it takes is a comparator watching the 555 ramp.

And fit to this TC:

http://analog-innovations.com/SED/Al...egulatorTC.pdf


At the moment I'm just considering my options - my motorcycle battery
needs
significant distilled water replacement 2 or 3 times a year, not just
topping up, it gets to the point that the starter is really sluggish and I
find the electrolyte only half way up the plates.

Is this rate of water loss excessive?

So called "black boxes" for motorcycles are at notoriously extortionate
prices (assuming the part is available for a 30 yr old motorcycle) so if
replacement becomes neccessary, a home brew might be order of the day.


Excessive water loss is due to overcharging. Follow the
voltage/temperature curves I referenced and you'll do a lot better.

I'd roll my own from discrete transistors on a PCB, and protect
carefully against transients.

Is your field switched from positive? Most stuff today is the other
way around, to allow NPN or NMOS field drive.


Good question - the workshop manual diagram just shows 2 wires from the
alternator field to the control box, no reference shown of either to +12 or
ground.