This time I'm playing with Dave's constant current load circuit.
The control voltage varies from 0 to 5V via a voltage divider. I've got two problems, though. First, I can't get more than 1.7V across the 10 ohm resistor, even with the control at the full 5V. And second, the HEXFET gets hot, even though the current through it is only 0.17A (1.7V/10ohm).