Re: [CAD_CAM_EDM_DRO] Re: CNC Etch-A-Sketch, EggBot

As a second thought, you might want to use a second cable pair just a smidge
higher than the one I discribed below. That way you'd have an additional signal
to let you know that the pen is starting to press in a little too hard, and it's
time to back off a hair.

Bill

On Fri Jan 4 12:32:19 2002, Alan Marconett KM6VV, <KM6VV@...> wrote:

>Hi Bill, Ballendo,
>
>That could work, if I follow you! And that reminds me, there are
>"reflective optical switches", as used in the tach circuit, that would
>be easy to use to digitize the surface of an egg. The MaxNC probe
>doesn't use much pressure; I'm gonna chuck up an egg in my new sherline
>4-jaw chuck mounted on a rotary table, and digitize it!
>
>Ballendo, I had previously missed your comment, as copied below. Yes, a
>cantileaver pen "tracker" would seem useful, however it imparts some
>lateral motion as well as vertical motion to the pen.
>
>Alan KM6VV
>
>
>Bill Vance wrote:
>>
>> Just thinking about it, an optical sensor might be of use here. Normally, an
>> optical cable Y connector is used for this version. Drill a tiny hole in the
>> end of an LED, ans insert a piece of optical cable with a drop of clear cement
>> on it, and let dry. Insert the other end into one of the top arms of the Y
>> connector, and do the same thing to the other arm with an optical sensor diode/
>> transistor. Attach more optical cable to the bottom arm of the Y, and use the
>> other end for a sensor probe. When light from the LED is reflected from
>> something close, a certain amount of light goes back up the cable to the sensor
>> transistor, and gets electronically detected, outputting a signal.
>>
>> This is probably not quite accurate enough distance-wise, but a two cable
>> version could be. Set it up such that the LED cable points light across the
>> front of the tip of the sensor cable. When the sensor gets a reading you know
>> that the tip is right next to where you want to be, and the pen needs only N
>> silly millitweeters more travel to be in contact. When the signal goes away,
>> it's time to bring it back down before continuing. Dead simple.
>>
>> Bill
>>
>> On Thu Jan 3 17:21:46 2002, ballendo, <ballendo@...> wrote:
>>
>> >Alan,
>> >
>> >The simple thing is to use a parallelogram (think rear
>> >derailler,10speed) on the "pen" axis...
>> >
>> >Hi-tech would be to sense the surface, either by contact/retract (not
>> >good as it marks up the egg!) or with a small "angular laser"
>> >distance module...
>> >
>> >Hope this helps.
>> >
>> >Ballendo
>> >
>> >> > I'm wondering if any of our CAD/CAM *EGGHEADS* can suggest ways
>> >to track
>> >> > an egg's surface?
>> >> >
>> >> > Alan KM6VV

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