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Old Jan 17, 2004, 10:32 AM
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Budapest
Joined Jul 2003
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I am not sure that A/D conversion is really necessary. Probably a comparator do the job. On the other hand, a/d is built in and cheap, so why not...

A draft idea:
- the absolute phase angle seems not really critical, in my controller I can set it from 0 to 30 degree, not too much difference
- it is possible to sample the comparator several times, as the emf is a linear ramp, the result is very similar to A/D conversion
- as drive is pulsed, there are distinct time windows when emf measurement possible (if the fets are open, no measurement possible)
- sample the signal at the window in the middle, and in the window before and after
- smooth the angle representative digitally, add or substitute slightly according to the middle window sample if the side window samples are correct
- or correct it radically if the angle error is so high that one of the side window samples is incorrect

Something like that...
The following is oscillogram of a CDrom motor - Jeti controller drive (the upper trace just marks one full turn of the shaft)
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Last edited by mmormota; Jan 17, 2004 at 10:41 AM.
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