Pumping Station: One

Once again, x has gone missing. Help us find him!

Join us for an evening of math and learning. There’ll be spheres and equations and integrals, (oh my!). We’re open to anyone looking to brush up on basic skills and to those who want to learn a bit about advanced topics. We’ll be talking about set theory, topology, linear algebra, logic, geometry, and anything else that comes up.

All levels of math skill are welcome. Whether there’s something from grade school you never understood, or you’ve always been fascinated by something a bit beyond you, come and ask. Got a homework question? We can help! Working through a tricky problem for a project? We’ll think it through with you. Confused as to how anyone could ever like math? We’ll do our best to convey the elegance and beauty of the subject.

Show and Tell

At the start of this week’s Math Office Hours, we’ll be doing show and tell. If you have a math topic you’re interested in, come tell us about it.

Last week’s talks included:

• Non-Euclidean Geometry, the discovery that Euclid’s ancient laws of geometry work just as well on a curved surface such as a saddle or a sphere if you reject the parallel postulate.
• A proof that given two complex numbers, the magnitude of their product is the product of their magnitudes.
• A Math Olympiad challenge: Given two primes p and q, show that 24 is a divisor of p^2 – q^2.
• Manifolds, a basic example of charts and change-of-coordinate maps. The configuration space of a double pendulum as an example of a non-physical manifold.

Whos, Whens, and Wheres

• Who - Anyone who wants to learn about math
• Where - PS:One, second floor, in the electronics area
• When - Sunday, June 23th, 5pm until 7pm
• How much - Free

Tonight at NERP, we’ll have two presentations.

Brian Chamberlan will tell us about using Erlang to program/control the RaspberryPI/BeagleBone. Erlang is a functional, general-purpose concurrent, programming language and runtime system. Erlang provides language-level features for creating and managing processes with the aim of simplifying concurrent programming. Processes communicate using message passing instead of shared variables, which removes the need for locks. [paraphrased from wikipedia]

Michael Beck will show us how to set up Xbox Media Center, XBMC on the Raspberry Pi. Pretty much every possible mode of interacting with a digital media stream is supported by XBMC. The Raspberry Pi’s excellent (but proprietary) video rendering hardware makes it an ideal platform for building a home media center.

NERP is not exclusively raspberry pi, the small computer interest group atPumping Station:One in Chicago.

Find NERP and Pumping Station:One
at http://www.meetup.com/NERP-Not-Exclusively-Raspberry-Pi/
and http://pumpingstationone.org/

NERP meets at 7pm 6-17-13 at Pumping Station:One, 3519 N. Elston Ave. in Chicago.
Doors open at 6:30pm. NERP is free and open to the public.
Ed Bennett ed @ kinetics and electronics com

The project was to build a “single axis” drawing machine in one night.  This machine uses two independently controlled carriages on a single piece of MakerSlide rail to control a pen at the tip of two linkages.  The primary purpose of the project was a fun group build and a learning exercise in setting up a non-Cartesian machine using inverse kinematics.  Kinematics in this case means mathematically describing the machine to the CAM controller.  The One Axis DrawBot is a very simple non Cartesian machine.

The equations used are shown above.  The ends of the linkages on the carriages end are at Xa and Xb.  The pen is at X1, Y1.  The first two equations convert the desired pen location back to actual machine locations.  They were plugged into the CAM program.  The last two equations do the opposite and convert machine locations to the pen location.

We had one team assemble the machine, one team wire the electronics and one team setup the controller.  It took about two hours to complete that phase.  We try to use newbies wherever possible, so adding solder training into the mix usually adds a little time.  The next step was to setup the CAM controller.

We borrowed the  CNC router computer and control box to run the machine.  This has Mach3 CAM controller software on it.  Mach3 has a “formulas” feature that we used to enter the kinematics.  We quickly had the machine running, but it was soon clear that Mach3 was not completely up to the task.  In the formulas mode, it appears to disable the DROs (digital read outs) which tell you exactly where the machine is.  It was also difficult to home or tell the machine the current location.   Moves in the Y axis are non linear and need to know the current location.  This resulted in Y axis moves that were not 100% accurate.

The other problem was coordination.  If you tell a CNC machine to move from X0, Y0 to X1, Y0,  it accelerates up to the desired speed then decelerates to the end point.  If you tell it to move from X0,Y0 to X1 Y10, the two axes are moving different distances, so it needs to coordinate the different axes speeds and accelerations. The X axis would move quite a bit slower to coordinate with the longer Y distance to get a straight line.  Mach3 was coordinating the two machine axes, but it was not coordinating the pen axes.  Moves in only X or only in Y were nice and straight, but moves in both X and Y had a bit of a curve to them, but they did accurately arrive at the end point.  A graphic with a lot of short moves would not show any on the problems above so we ran a quick “PS:One″ graphic.  Watch the video and be sure to wait for the applause.

We will switch to using EMC2 (LinuxCNC).  This has a true inverse kinematics feature that should fix the problems.

This week the CNC Build Club is going to attempt Gonzo Build #2.  A gonzo build is where we try to knock out a complete CNC project in one night.  Gonzo build #1 was the Quantum Delta 3D printer.

Quantum Delta 3D printer

This week we are going to build a one axis 2D drawing machine.  This uses two independently controlled carriages on the same axis to get 2D motion at the ends of the linkages.  The purpose is only to have a little fun and to cut our teeth on a simple inverse kinematics machine before moving onto a much more complex 6 axis machine.

If you want to help, please join us.  The meeting is open to non members.  Please RSVP via meetup.

Raspberry Pi Video Camera, BoneScript on the Beagle
NERP is not exclusively raspberry pi, the small computer interest group atPumping Station:One in Chicago.

We’ve been wondering what it’s like to work with the new Raspberry Pi camera module. Tonight we’re in luck. Craig LeMoyne has a Raspberry Pi project he’ll show us tonight. In his words:

“I have an RPi Model A in my basement running Apache2 and taking pictures
using the new Camera Module every few seconds of a wet area that I *hopefully* managed to patch. It is good fun, and I can also do timelapse video from the pictures. The Pi will even compile the timelapse for me!”

Drew Fustini will introduce us to programming the Beagle Bone Black in BoneScript.
I’ve been saying for years that Javascript would be the next hot language for microcontrollers – maybe it’s true. From beagleboard.org/Support/BoneScript

“BoneScript is a node.js-based language specifically optimized for the Beagle family and featuring familiar Arduino function calls, exported to the browser. Get started exploring the BoneScript Library to discover the great simplicity that is made possible by utilizing Linux in BoneScript.”

Find NERP and Pumping Station:One
at http://www.meetup.com…
and http://pumpingstation…

NERP meets at 7pm 6-3-13 at Pumping Station:One, 3519 N. Elston Ave. in Chicago.
Doors open at 6:30pm. NERP is free and open to the public.
Ed Bennett ed @ kinetics and electronics . com

Last night’s meeting was great.

The craft and textiles area at PS:One is visually dominated by an eight foot by four foot table.   The table is a handy work surface for projects of all kinds, but the main reason it is so large is so you can lay out long, full widths of fabric for sewing. 

It usually looks something like this, covered up by a protective heavy grey vinyl tablecloth:

Underneath is a clean, firm, pin-able and iron-tolerant surface perfect for working with flat patterns, even for long dresses with full skirts, and laying out quilts.

Tables like these are used in theatrical costume shops, custom bridal gown workshops and custom drapery shops.  It was easy to build, I just made a basic table with bolt-on legs and a sheet of plywood, stacked a sheet of Homasote on top and wrapped the whole thing in stapled cloth.

Not only is a cloth-covered table like this perfect for straightening the grain of the cloth before cutting, it is perfect for drafting sewing patterns and grading because you can pin the paper down so it won’t move.  And it is a phenomenal tool for tracing existing patterns.

Here, I have a vintage blouse pattern from the 1940′s.   The paper is so old and fragile it is starting to tear.  Rather than potentially ruining the antique original by using it, I traced a copy of it before going any further.

To do this, I laid the pattern out on the table and ironed it very lightly with a cool, dry iron to flatten it.  Next, I laid large pieces of tracing paper over it which I pinned down to the table at the corners.  I also put pattern weights over the pattern to help keep it flat and ensure it wouldn’t move.  Then I just traced it out.  It beats the heck out of trying to do it on the floor, or on a too-small table!

Yes, I use big washers for pattern weights.  Originally I was going to cover them with cloth so they’d be more grippy, but I love that I can store them easily this way.

Image via Boing boing via Fablocker.org

When: Thursday, 2013-05-30 @ 7:00pm.

There is no special topic or speaker for this week’s meeting, but here are a few things we will be doing.

• Member Certifications: Colin, Steve and I can certify on various pieces of CNC equipment including the Laser Cutter, Vinyl Cutter, 3D printers and CNC Router.
• ABS Smoothing: Donald J is hopefully going to bring in his acetone vapor chamber for ABS print smoothing.  Bring your ABS parts and a any spare fire extinguishers you have.
• DSP Stepper driver tuning. I now have a programming cable for the drivers.  We play with and learn about the benefits of stepper driver tuning.
• Another group, gonzo CNC build? It might be fun to plan another gonzo build.  We could kick around some ideas to try to build in one night again.  I think a simple inverse kinematic (oxymoron?) project might be fun.  Eventually I want to do a six axis machine, but it might be good to get our feet wet with a non Cartesian 2 axis draw bot.  If you have other ideas, please suggest them.

I can bring in a few sample of V carving.  We might do that the following week.

Please RSVP via Meetup if you are coming.

Good news! Instructables have started sponsoring monthly build nights. And the more tutorials we make, the more supplies and equipment they’ll send us.

This month, we received a whole bunch of Bare Conductive Paint Pens. Tomorrow night at 7pm, we’ll spend a few hours playing around with them. Come experiment with the wonders and dangers of paper circuitry!

Express your inner mathnerd! Come join us for an evening of learning: algebra, calculus, word problems, finding x, and much, much more. We’re open to anyone looking to brush up on basic skills and to those who want to learn about more advanced topics. We can even stray into set theory, topology, and fourier analysis…. it’s all up to you!

If you’re feeling intimidated, don’t be. Any level of math experience is welcome. We will be happy to discuss any topic that falls under “math”. No question is too basic. Got a homework question? We can help! Trying to solve a tricky equation for a problem? We’ll think it through with you. Want to learn the basics of what math is all about? We’ve got you covered!

Math should be a common language to all, and we will be more than happy to help you take the first steps towards a lifelong appreciation of this beautiful subject!

Whos, Whens, and Wheres

• Who – Anyone who wants to learn about math
• Where – PS:One, second floor, in the electronics area
• When – Sunday, May 26th, 5pm until 7pm
• How much – Free