On Sun, 2012-03-18 at 10:15 -0700, Peter C. Wallace wrote: ... snip > Hall effect sensors are one way. They have the advantage of simplicity and > not > requiring floating power on top of the swited leg. TI makes some nice > isolated > current sensors (like the AMC1204) > > current sense resistors in the low side can also be used but the pair of > resistors that are sampled and the exact sample time must be chosen carefully > depending on the PWM waveforms (High side series sensors have the advantage > the they dont see the switching only the ripple)
Thanks for your reply Peter. One application I am thinking about is sensing current in one of the motor leads from a KBIC SCR driver. I believe these leads float pretty widely from mains ground. The KBIC's internal current sense floats too, so there is no problem. I have a setup on the bench that uses an ATmega32 that runs Modbus, plus Speed PWM and bit I/O through opto-isolators. I'd like to add motor current to the Modbus reply data (motor voltage would be nice too), but the floating motor leads seem to be an issue. Thinking a little more, I suppose I could float the ATmega along with the KBIC and isolate the TTL side of the RS485 chip. This puts me into thinking about floating supplies. On the other hand, if one where to go to the trouble to put an AVR onto a KBIC, it would be better to just design a new DC motor drive based on the AVR, maybe. -- Kirk Wallace http://www.wallacecompany.com/machine_shop/ http://www.wallacecompany.com/E45/index.html California, USA ------------------------------------------------------------------------------ This SF email is sponsosred by: Try Windows Azure free for 90 days Click Here http://p.sf.net/sfu/sfd2d-msazure _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
