scone opendro lcd finished

[Bruce Fairman]

i just finished assembling a second lcd dro, using tactile thru hole switches (same as dro 350) with hand wired boards for the main keypad and the lcd/zero/line switches. it was a pain to do the hand wired boards but i am not ready to do pcbs. the whole thing was straight forward, easier than dro350 assembly. i used a 550 board that had no LEDs populated and i removed the surface mount tactile switches for better clearance, which was problem since the layout used the internal conductor between switch pins as part of the circuit (who'd have thought!). so i had to wire up the 550 to add the missing conductors. but no biggy.
i am going to use this dro with my lathe wth ditron scales which does not need a different silk screen that the mill version.

there are 3 boards, the 550, a main keypad and an lcd and display line oriented switch board, all real simple.
when i get the scales attached, i will make another video showing the ease of use improvements.

--Thanks,
bruce
KE6OKC

[Rick Sparber]

Bruce,

I'm glad to hear you are still plugging along on this project. I'm
completely out of touch with the SumaTech community. Is the 550 still for
sale? I believe the newest version is the 375. How does that compare to what
you have done?

I've spent most of the summer perfecting a new Electronic Edge Finder to be
used primarily on a lathe. You just connect up the two probe wires and it
can detect when the cutter touches the work piece (assuming the work piece
is conductive). This required me to be able to detect a 3.2 micro volt
change with as much as a 100 micro volt RMS noise level. Seems to work so
far. The circuit uses one quad op amp, 4 transistors, and 3 LEDs plus runs
on a single 9V battery.

I have a few videos of various version on YouTube.

http://www.youtube.com/user/rgsparber1?feature=mhee

I have not written up the circuit yet but will do it soon.

Rick

[Bruce Fairman]

Rick, yes, still plugging away. iÎ had an idea on edge finding that considers repeatability. the resistance method you are using may have some issues with repeatability since the resistance at various parts of a surface will vary. i thought of using a pressure sensitive resistor device with a spring loaded probe. the method is to calibrate the edge sensor to a particular contact force using an a2d input and then subsequent senses would be complete when the resistance is the calibrated value. i got as far as getting the sensors, but haven't done the electrical part yet.

--Thanks,
bruce
KE6OKC

[Rick Sparber]

Bruce,

Sorry for the very long delay. Was on vacation and just got back.

The method I am using does not see the absolute resistance. It only responds
to changes in resistance.

I can't use anything between reference surface (the work piece) and the tip
of the cutter because it introduces another variable. I'm able to just
connect up two wires and go for touchdown. If I was able to put something
between the work piece and the cutter, it would be a sandwich of two
conductors separated by an insulator. Then I would only need a simple
continuity tester.

[Bruce Fairman]

Rick, i hope you had a fun vacation!
have you characterized the repeatability of the sensing scheme that you are using? i would imagine this could be done using a test indicator and touching down at the same point multiple times and then touching down at a series of points and noting the test indicator. this would be on a surface that is parallel to a direction of motion.

--Thanks,
bruce
KE6OKC

[Rick Sparber]

Bruce,

Vacation was fun. Getting home was not. We were supposed to go through JFK
about the time the hurricane hit. Ended up traveling from early Wednesday
morning until Friday morning. Ug! Still have some jet lag....

I don't think repeatability is an issue because we just have the cutter
moving until it touches the workpiece. It is not like there is something
between the two points. If anything, the EEF is more accurate than the DTI.