Where is NJC t? What is he about? Whither dost he wander?
Side projects are popping up more side alleys than any sorcerer's nightmare. I need, eventually, to get to project A. But it will help to do project B first, both because having B will help with A and because if I don't get B outt of the way, it will be in my way while I work on A. And then ...
In thinking about how to test B under severe-but-realistic load, I've been thinking about project C. Which started small, but quickly became interesting. I spent most of yesterday filling pages with algebra to understand the non-linearities of parallel-series combinations of fixed and variable resistors (both as potentiometers and as rheostats). My bladder woke me overnight and as I took care of business it occurred to me that I could (probably) finesse the problem with current sources. Looks workable, but will be ten hours or more of lab work. LATER. I just now thought of a useful mod for project B. I'll try to do it. And project C has a detail to be worked out using an RC network to drive a MOSFET to provide a brief, fast reset current to the timing circuit on each side of an astable multivibrator. (The MOSFET's gate may be approximated as a capacitance that depends on the voltage on its drain terminal.)
I've got a circuit layout for project B to breadboard and test. I need to do a clean drawing of the layout, and I need to test it in parts: Current source, three-way current mirror, and voltage source. The voltage source first with only the voiltage output, on the circuit board, and then with the power block (not complete yet) including both the voltage output and the current bootstrap transistors.
And then I need to test it. Unfortunately, I passed up the chance to stock up on 5- and 10-ohm 10-watt sand-cased power resistors.
And, oh, yes, The Rockpile.