Alright, this is what I have so far for a schematic. This is for positive or negative ground, 20/30/40/50A selectable current regulation, and 6/12V (7/14V) voltage regulation. This one is only for self-excited generators, the only type that Packard used AFAIK. Though this could be modified without much difficulty to accommodate separately-excited, or even both on the same design, the chance of swapping generator types on the same car is so small, to one that Packard never used, that it's not a design priority. That being said, this design is not Packard-exclusive, and should work with any car with a self-excited generator.
If you're not familiar with the difference between self- and separately-energized generators, read this parenthesis:
As I understand it, there are two basic types of shunt-type car generators. If the generator field is connected to arm internally and the regulator adjusts the resistance between the field terminal and ground, then it's a self-excited generator. If the field is grounded internally and the regulator adjusts the voltage provided to the field terminal, then it's a "separately excited" generator.
According to the service book, '55 (and I assume most/all other) Packards used the former. One can tell by excerpts of the manual: self-energizing will increase output when F is grounded. Separately-energized will decrease output.
Note that this is regardless of voltage or polarity (assuming that all the correct polarity components are being used).
Anyway, on the schematic:
- To connect it, connect BAT to the "ARM" of whatever type of ground the car has. For example, on a negative ground car, connect BAT to "ARM –". Then connect generator ARM to the other "ARM" terminal. For FLD, ground the "FLD" of whatever type of ground the car has. Then connect generator FLD to the other "FLD" terminal.
- The DPDT switch near the bottom is for 6/12V selection.
- The SP4T switch near the center (modeled as an IC) is for current selection.
- The "MLX" IC is an ammeter, which outputs a voltage on Vout proportional to the amperage.
- The transistors near the bottom are there to get the voltage read from the actual armature sie, regardless of type of grounding, and to avoid a short circuit around the ammeter and Schottky diodes (which would occur if just diodes were used).
- Two different ground symbols are used: the "lined" ground is chassis ground; the "triangle" ground is only to mark in common some connections on the board, and is not directly connected to the car ground. This is because the electronics would not work with opposite grounding otherwise; the car's current is rectified and then sent to the electronics that require it.
Very complicated-looking, I know; it was hard to clean up the schematic. But I think the design is solid enough with hopefully no or few errors at this point, just details that need added. Sometime soon I'll be finishing up the exact component choices and trying to breadboard it.
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