Friday, October 5, 2012

The Electronic Quick Change Gear Box, part 3

(continued from part 2)

The Control Panel

Refer back to part 1 of this series to see pictures of a real quick change gearbox.  My electronic version will be similar.

The circuit boards and switches will be contained in a box that's perhaps 10" x 5" x 2".

The real QCGB has two levers on the bottom.  I'll use rotary switches.  I recently purchased two mil-spec 8-position switches for this project.  They're excellent.  I was originally going to use 10-position switches but it turned out that 8 positions are plenty.  These two switches will yield 64 threads and feeds.

Here's a sample of what the control panel might look like.

The chart on the left tells the operator how to set the two 8-position rotary switches.  The chart itself has three sections; rows A-D are for standard threads.  For example, the "10" in that section of the table means 10 threads per inch.  Rows E and F are for feeds.  They may be thought of as very fine threads.  The tool used for feeds will be purposefully ground so as to obliterate any thread artifacts.  Rows G and H are for metric thread pitches, in millimeters.

The two circles below represent the 8 position rotary switches mentioned earlier. The switch on the left selects the row and the switch on the right selects the column.  For example, if you want a 13 TPI thread, you'd find 13 in the upper 4 rows, then set the switches to B-6.

Small circles represent 10mm LEDs.  The column of 4 LEDs to the center-right tell the operator how the selected thread relates to the lathe's threading dial.  Most of the time the "choose any mark or number" LED will be lit.  If cutting metric threads, the "Do Not Disengage" LED will be lit.  A few oddball threads will cause one of the other LEDs to be lit.

The rectangle below these LEDs (and the other similar rectangles) represents a toggle switch.  This one supplies power to the electronics and the stepper motor.

Finally, moving to the rightmost column includes controls that have nothing to do with the QCGB but are included since they must all work together ergonomically.  The toggle on the bottom causes the lathe's motor to start running.  The circle above that is a knob that controls the speed of the motor.  The toggle on the top determines the direction the motor spins.

I expect to mount the control panel on the left end of the lathe making the power switch the most easily accessed control.  Seems prudent.

Part 4 continues here...

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