I've been building PIC-based "gadgets" for my 31' sailboat for a couple of 
years now: bilge pump controller, refrigerator controller, 
all-singing-and-dancing battery monitor/amp-hour meter, and this winter my 
project is a sophisticated alternator regulator. I have a commercial one 
that works just fine, but that's no fun! I want to build my own.

My area of concern is the "regulator" part - there are some areas I've no 
experience with, and would appreciate some advice.

I will use PWM to drive the alternator field. The question here is what 
sort of pulse rate should I be using? The field presumably looks like a 
large inductor (I've not a clue as to what the inductance might be) and a 
series resistance (which I can measure). Should I use a real low PWM rate? 
High? Not a clue as to what I should use.

Second area of concern - I've built analog regulators before with no 
problems (benchtop supplies, etc), and in fact I built an analog regulator 
for a boat alternator as well. But in the case of a digital control loop 
for a system such as an alternator, is a PIC (e.g. an 18F series unit) 
going to be fast enough? I've no idea what sort of response time I need. 
Given that the battery is more or less a huge capacitor, and that changes 
in the source side (the alternator driven by the engine) are very slow, I 
expect that there is plenty of time for a PIC-based PID loop to handle 
things. Anyone got any experience in this area?

I thought of using a dsPIC for the project - are these devices "mature" 
enough to use in a real application yet? I recall some of the problems with 
the 18F452 that caused me grief with my battery monitor project.

Thanks for any advice, suggestions, etc.

Larry Bradley
Orleans (Ottawa), Ontario, CANADA 

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