[modeleng] Re: Topsy - to charge and how to charge, that is the question!

A thought on Topsy's charging circuit.

If Peter uses the diode to protect the alternator, and manages to take 
the feedback from the battery side of that diode (the cathode - the 
confusions over which part of a diode is "the plus" support my long held 
feelings that "plus" and "minus" don't identify anything on a diode, 
they just add to the confusion, but I'm wittering now....)

The only problem now is how to stop the load from the alternator 
stalling the petrol engine. Since the field current is controlling the 
alternator output, why not put a resistor in series? I realise that the 
control loop will try even harder to push more current through the 
field, but there is a limit when all 24V is being supplied. Of course, 
the resistor would have to be found by trial and error, but I'd guess a 
maximum value of 4 or 5 times the field resistance.

I have to say I've never tried this idea, and the stability of the 
control circuit may go awry, but it does have the advantage of being 
cheap and providing something for the driver to warm his hands on!

Can anyone on the list confirm that this will work or not?

JohnP

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