Electrical Musings

So many people on the net know about Sparkfun. It is a quirky website out of Boulder Colorado that sells electronic kits/gadgets/pcbs/components for building your own whatever. They concentrate on Ardunio type single board computers. Today was "Freeday" where they gave away $100 to the first 1ooo customers. But before today they made a big deal about how they tuned up their servers to handle the load. Maybe they were a bit optimistic but MANY people who tried to participate (including myself) spent 2 hours hitting "refresh" when all we had to do was click "confirm order." Now I (and many other people) have a huge level of frustration that because the site wouldn't let us through, we lost out. In other words the "free" offer was not played fairly because their servers slowed to a crawl. I would totally accept having the money go quickly (in something like 5 minutes) and I just missed out. But clicking refresh for 2 hours (literally

There are lots of code example that show rotation or a 2D point around the origin but what about around some arbitrary point? This is important if you are translating airfoils into G-Code... To do a rotation around a point without matrix math you translate the point to rotate around the origin (0,0,0), then rotate the point, and translate it back. So basically you subtract the location of the rotation point from the x coordinate, rotate the new point, and add the location of the rotation point back. Here it is in Python from math import * def rotate2d(degrees,point,origin): """ A rotation function that rotates a point around a point to rotate around the origin use [0,0] """ x = point[0] - origin[0] yorz = point[1] - origin[1] newx = (x*cos(radians(degrees))) - (yorz*sin(radians(degrees))) newyorz = (x*sin(radians(degrees))) (yorz*cos(radians(degrees))) newx = origin[0] newyorz = origin[1] return newx,newyorz

The following Python script produces a parabola in G-code. #This code produces g-code for a parabola using the equation #(y - k)2 = 4a(x - h). The parabola is open to positive x. #a = x coor of focus #k = x coor of back of parabola #h = y coor of focus #r = resolution #ymax, ymax = limits of iteration a = 2.0 k = 0.0 h = 0.0 ymax = 5.0 ymin = 0.0 resolution = 0.1 lastx = 0.0 lasty = h def frange3(start, end=None, inc=None): """ A range function, that accepts float increments... http://code.activestate.com/recipes/66472/ """ import math if end == None: end = start + 0.0 start = 0.0 else: start += 0.0 # force it to be a float if inc == None: inc = 1.0 count = int(math.ceil((end - start) / inc)) L = [None,] * count L[0] = start for i in xrange(1,count): L[i] = L[i-1] + inc return L #top half for ystep in frange3(ymax+resolution,ymin,-resolution): x = ( ((ystep - k)*(ystep - k)) + 4*a*h ) / (4*a) print "G01 X"+str(x) +" Y"+str(ystep)

In a response to Where the heck? What the he11? HUNH? on CNCZone I posted the following. I realized later that it is a good summary of my retrofit so I will repost it here. I am in the process of doing the same thing (a Bridgeport Boss CNC Retrofit). I have the gecko drives working, a Automation Direct GS2 VFD, and a power supply built with T1 (the 240 v to 120v transformer tapped at 40v). I already had Gecko 201s but the 203s would be better because of the auto short circuit protection circuitry. Just remember that "common" on the Gecko 201s is 5 volts to power the opto-isolator LED. Also just wire 2 windings of 4 of the stepper motors because the windings are in bifilar (which means that 2 windings are wound together). There are jumpers on the motors that show which terminals are the ends of the windings and then wire to the other side. I have 1 sigma and 2 superior and the geckos work fine so far. I used a C11G breakout board from CNC4PC which has some extras AC relays f

I have frequently bought from Enco because their prices are much better than other places especially if you shop from the Enco flyer. Recently a machinists vise came up on sale. It is a presumably Chinese copy of a Kurt vise and seemed a good deal. However, while all the "good" vises such as Kurt or Parlec gave some kinds of specs for repeatability, flatness or parallelism the Angle Tight II ads listed nothing but holding force. So I emailed Enco... to EncoTechandParts@use-enco.com date Thu, Sep 24, 2009 at 2:49 PM subject Angle Tight II Precision CNC Machine Vise PN SU327-5893 Questions I am interested in the Angle Tight II Precision CNC Machine Vise PN SU327-5893 that is on sale right now for $159.95. I want to use it as an inexpensive CNC vise but there are no specs published in the flyer or the catalog. What are the specs for accuracy, flatness or parallelism of the jaws? Is the bed ground to flatness? Also, do Kurt style soft jaws fit the vise? I am sure with some of

One of the first things that one needs to retrofit a Bridgeport Boss CNC machine is a power supply for the steppers. That is assuming that one has drives which I do in the form of Geckodrive G201s. The original Bridgeport power supply for the steppers put out 56 volts dc so most people use this voltage although some use 60 or even higher voltages. As far as current goes most people use 6-7 amps, 7 amps being the maximum that G201s will source. While researching stepper power supplies I found a great reference on Gecko's website. http://www.geckodrive.com/upload/Step_motor_basics.pdf This document not only shows how to wire the drives but gives a good example of a power supply with sample component values. Basically a power supply (unregulated) only needs a transformer putting out a desired voltage that is rectified by a full diode bridge and filtered by a big capacitor. To get 56vac you need un-rectified 39vac. (56 v /1.414 = 39.6 v) For a capacitor value C = (80000 u

Before I go much further I should note that I am new to CNC and machining in general. Which means I have no tooling. I do have a good set of import drills and a set of inexpensive end mills but no test indicator, to tool holders, etc. One of the first things I looked at when I got the machine was the taper. These machines came with 2 types of Quick Connect tapers, either QC#30 or Kwik Switch 200. My machine has Kwik Switch 200 which according to users of CNCZone is far superior to R8. Unfortunately tool holders are not as common as R8 or as inexpensive. The first tool holding device I acquired (or am acquiring) is a keyless chuck and a 1 JT Kwik Connect 200 adapter. This is what the one that I won in auction looks like. Although I did win the auction a while back, I have still not received the adapter. I first bought a 1 JT adapter but plan on getting a 2 JT and 3 JT adapters. I also bought a 5/15" keyless chuck for the 1 JT and will get a 3/8" for a 2 JT