CTIN 534

Video tracking drives stepper motor

A demonstration of how to use softVNS motion tracking to rotate a stepper motor.

Basic Stamp program listing
Max/MSP/softVNS patch
snapshot of stepper motor setup
closeup of stepper motor & switch

Hacking a servo for continuous rotation - links

http://www.gorobotics.net/articles/article.php?name=servohack
http://www.seattlerobotics.org/guide/servohack.html
http://www.acroname.com/robotics/info/ideas/continuous/continuous.html
http://www.dprg.org/projects/2003-05a/

The Future of Computing, circa 1983

From The Joy of Computers (1983) by Peter Laurie:

"To judge from the crowds round any demonstration of Lisa, it speaks loudly to the naive computer user. It remains to be seen how long people will be happy to pay what will always be a heavy extra price for the hardware necessary to mimic paper, rather than spend a few hours learning to do things in a more economical way. More seriously, it may turn out that although paper metaphors for computational ideas make it easier to sell machines to inexperienced users, in the long run it may be a sterilizing influence. As I have tried and will try again to show in this book, there are many aspects of computing which have no parallels in the familiar world of paper information. Sooner or later people who want to be 'computerate' will have to buckle down to the fact that computing is actually different from paper."

bibliography

Pretty much everything on my bookshelves (on this coast anyway), with some exceptions. The categories are somewhat arbitrary, and not everything is relevant, or even recommended. But most of it is worth reading.

Perry's Book List

Unipolar Stepper Motor Control

external links:
• Stampworks Experiment #26: Stepper Motor Control (PDF)
• ULN2003 spec sheet (PDF)
• BEAM Reference Library article on Stepper Motors
• Jones on Stepping Motors

internal links:
• Basic Stamp program (revised version of StampWorks program)
• circuit diagram (revised version of StampWorks diagram)
• snapshot of small stepper setup

links to components @ All Electronics:
• ULN2003 Darlington Array
• a small 12V 7.5 deg/step unipolar stepper motor
• a larger 5V 7.5 deg/step unipolar stepper motor
• a larger 5V 1.8 deg/step unipolar stepper motor

NOTE: You will need a separate power supply for the motor.

Sorting out the wires:

Unipolar stepper motors have six leads. Internally, they have two windings, each with three of the six leads. One of these three leads is a center tap on its respective winding; this lead gets wired to V+. The other two leads are connected to each end of the winding, and when either is successively grounded, it creates an opposite magnetic field. By alternately energizing the two windings in each of two directions, the rotor can be stepped in a clockwise or counterclockwise direction.

To sort out the leads on a unipolar stepper motor with 6 wires: Use a multimeter to measure the resistance between pairs of leads. Each pair of leads will give one of three possible results: a fairly low resistance, twice this resistance, or a very high resistance (typically in megaohms).

Try to find a trio of leads with low resistance. Of these three leads, the one that gives identical results with the other two is the common. The other two together should give you twice the resistance of either of them with the common. Label the two groups of three leads each 1 and 2 (don't worry about which is which; see below), and label each of the commons as C.

Now, if you connect the common to V+, by momentarily connecting each of the other two leads to ground, you should be able to make the motor shaft jump slightly clockwise and counterclockwise. Call the clockwise lead A, and the counterclockwise lead B. Find the A and B leads for both groups 1 and 2.

Each wire is now labeled: 1A, 1B, 1C and 2A, 2B, 2C. Connect 1C and 2C to V+, and connect the other wires to your control pins in this order: 1A, 2A, 1B, 2B. If clockwise and counter-clockwise are flipped once you wire everything up, then switch 1 and 2 (ie, 2A, 1A, 2B, 1B).

Julia Scher @ UCLA D/MA

The class consensus was to postpone the trip to see Scott Snibbe's show at the Beall Center until a later date so that we can make it to Julia Scher's lecture at UCLA on Wednesday @ 6pm. See you all there.

Dial-A-Movie

Here's the patch that I worked on with Mike in class. Put the patch in a folder with a bunch of quicktimes, open it up in Max, and use the dial object to flip through the movies.

Download Max patch

Full Week Ahead

Here's our (rather overbooked) schedule for the coming week:

Monday 11/10 4pm - 6:30pm: makeup class
Tuesday 11/11 6:30pm - 9:30pm: CTIN532
Wednesday 11/12 6pm - 8pm: Julia Scher @ UCLA D/MA
Thursday 11/13 6:30pm - 9:30pm: CTIN534
Friday 11/14 7pm - 10pm: Josh Clayton Jitter presentation

Basic Stamp to MIDI

Useful web site for MIDI hardware stuff:
DIY MIDI Controllers

Basic Stamp circuit diagrams

Basic Stamp program listing

3D image of BS2-MIDI setup

(flat) image of BS2-MIDI setup

H G Wells story

The story I mentioned in class last night is The Remarkable Case of Davidson's Eyes, and unfortunately I couldn't find the text anywhere online (although a number of other Wells texts are available at Project Gutenberg - be sure to search for Wells, H. G. exactly, the search engine isn't too smart). The story is included in The Country of the Blind, a $2 Dover book that you can usually find at any Barnes & Noble. Recommended.