On the subject of current sensing -
After more thought, I'd like to stay away from splitting the output busbars/pins/etc in order to add current sensing.
While the part P-hack suggested looks like a very good solution for this problem, it would still require adding a controlled impedance section... I suppose this could just be a thin part in one of the bus bars or connector pins... hmmm
The other option that would require this are the Allegro current sensors that are soldered to the bus bar.
In a general sense, I think non-contact sensors that use the magnetic field should be accurate enough for our purposes. Some of them require a flux concentrator, which is a gapped ferrite or laminate ring that goes around the sensed wire. The sensor fits in the gap. This would require some magnetic design to get right, but the ferrite might also serve the purpose of reducing stray EMI. A device from Allegro would be directly solderable to the main board with through hole pins, but would require an external field concentrator.
How do you guys feel about the issue of designing an external magnetic part (like a gapped torroid) for this?
Another option - would be the hall-effect sensors that don't require an external field concentrator. There is one made by Melexis that can do this and measure large nearby currents: - I think this is the one Paul made the daughter board for.
The MLX91206 is a contactless programmable current sensor
some advantages:
Isolated from high power circuit
Don't need external magnetics
Are spec'd for automotive use - - -50C to 150C storage and -40C to 150C operation.
Analog or PWM output
Issues:
requires calibration/programming
would require a separate "daughter board" that is perpendicular to the main circuit board.
- E*clipse