Re: ATM Robo-Foucault, Image intensity, and Changing knife edge readings

["Bob May" <bobmay@nethere.com>]

Jim, as to the thermal expansion fears, Take and drop the voltage if you can
to the motors until they so start messing up.  Then go into the software and
slow the clocking speed down until they tend to become reliable again.  If
they don't become reliable again, your speed is low enough that you don't
have to worry about dynamic problems.
I think that you will be able to drop the power down to 1/4 or less of what
you are running now without problems.
I'll also note that there are pulse techniques where the inital start of a
step is of one voltage and then the power drops as the motor stays in that
position.  You can do a very simple version of this by putting a cap and a
parallel resistor in the line.  The resistor sets the steady current to some
fraction of the max current and the cap provides the "snap" of the full
available voltage to get the motor started moving.  A more advanced version
would be to control the power supply with a pulsing level from the processor
as to when the step starts to some point after it has been there.
I'm not really happy with the color camera setup and would sort of prefer to
see a true luminance value rather than playing with the RGB to find the
strong one.  Also, having an overdriven image isn't good either.  That makes
it difficult to find the midpoint of the grayscale of the shadows.
Bob May
http://nav.to/bobmay
bobmay@nethere.com
NEW! http://bobmay.astronomy.net