From: W. Trevor King Date: Fri, 19 Nov 2010 13:22:36 +0000 (-0500) Subject: Finished importing my old stepper main page. X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=4e75f0e2cc4378bb6e58bfe6a5be23d1eda832ed;p=blog.git Finished importing my old stepper main page. --- diff --git a/posts/MultiMode.mdwn b/posts/MultiMode.mdwn index 7774bc9..78dc8b4 100644 --- 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 0d27250..65be89d 100644 --- 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 new file mode 100644 index 0000000..2b103ab Binary files /dev/null and b/posts/MultiMode/stepper/step_size.png differ