Finished importing my old stepper main page.

diff --git a/posts/MultiMode.mdwn b/posts/MultiMode.mdwn
index 7774bc93bbd6207ce274000f8b879311beaebf8e..78dc8b4f2ce7e067b9fe317431be57865969a5b3 100644 (file)
--- a/posts/MultiMode.mdwn
+++ b/posts/MultiMode.mdwn
@@ -4,7 +4,7 @@ was aquired by [Veeco][] in February 1998 before being passed off to
 [Bruker][] in August 2010.
 
 I've done a good deal of troubleshooting to keep our ancient MultiMode
-II, stumbling along.  If you're in a similar situation, check out my
+II stumbling along.  If you're in a similar situation, check out my
 notes on:
 
 * [[Stepper motor control|stepper]]

diff --git a/posts/MultiMode/stepper.mdwn b/posts/MultiMode/stepper.mdwn
index 0d27250343d167069de7ca0dd432e111dd612ed2..65be89da6720bca2a19d3ad4b7d9feaf4afbc904 100644 (file)
--- a/posts/MultiMode/stepper.mdwn
+++ b/posts/MultiMode/stepper.mdwn
@@ -126,14 +126,52 @@ the right hand screw) that it is labeled `5 V DC`, and `5 V` over a
 `20 Ohm` half-winding gives a current of `I = V/R = 0.25
 Amps`. Following the motor leads back up the the main board (using the
 ohm-meter guess-and-check method :p), we find that they come from the
-DS3658N (chip 1). This chip takes care of all the details of sinking
+[DS3658N][] (chip 1). This chip takes care of all the details of sinking
 the large motor currents given a TTL driving pattern.
 
-WARNING!  I strongly suggest you don't do this on your own. The high
-voltage lines for driving the piezo are potentially dangerous,
+WARNING!  I strongly suggest you don't do this on your own. The *high
+voltage* lines for driving the piezo are potentially *dangerous*.
+
+The control for the DS3658N was too difficult for me to trace out on
+the board, so I put the main board back in the MultiMeter (leaving the
+base-plate off), connected the Multimeter to our NanoScope IIIa, and
+started clicking on the ‘raise’ and ‘lower’ tip buttons. At the same
+time, I watched the various DB-25 lines on the oscilloscope.  DB-25
+lines 1, 2, 15, and 16 oscillated, but only when the motor was
+turning, so I figured they must be direct TTL controls getting
+(somehow) to the DS3658N. I built a DB-25 breakout box to take control
+of those lines, and started writing software.
+
+Line roles
+----------
+
+Knowing the stepper control lines and how to control a unipolar motor,
+it was only a matter of matching the lines to the roles. I arrived at
+the matches that I pointed out in the *How* section through trial and
+error. It was fairly easy to get the motor moving macroscopically, and
+[[backlash]] testing convinced me that the microscopic motion is
+reproducible and smooth.
+
+Stepsize
+--------
+
+We measured the stepper stepsize by stepping the AFM tip closer to
+surface and sweeping the piezo in after each step.  This produced the
+data shown below.
+
+[[!img step_size.png
+  alt="Measuring the stepsize"
+  titl=e"Measuring the stepsize"]]
+
+As the motor steps in, we record consecutive traces a, b, c, d, e, and
+f. Because we can calibrate the piezo by imaging a calibration sample,
+we can convert our piezo voltage into the distance shown on the `x`
+axis. Measuring the `x` distance between to traces, we see that the
+sample moves ~170 nm closer with each step.
 
 [NI]: http://www.ni.com/
 [DJ]: http://www.cs.uiowa.edu/~jones/
 [tutorial]: http://www.cs.uiowa.edu/~jones/step/
 [drive]: http://www.cs.uiowa.edu/~jones/step/types.html#unipolar
 [unipolar]: http://www.cs.uiowa.edu/~jones/step/types.html#unipolar
+[DS3658N]: http://www.physics.drexel.edu/~wking/rsrch/multimode.shtml#chips

diff --git a/posts/MultiMode/stepper/step_size.png b/posts/MultiMode/stepper/step_size.png
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