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Danny
08-09-2005, 05:44 AM
Next issue/problem. Bought a sherline mill, seriously cool machine, not as nice as WEBECO but perfect for my inventing projects.
I want to put a tach on it similar to ?Chris'? but was interestedin using a black/white stick on wheel that sherline provides on their site with an optical sensor and a stamp driving an LCD display. My question is can I use the QTI line sensor to see the black/white disk spinning under it or is it's response time too slow for such a project??

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"Never create anything you can't control"
"The amount of intelligence on the planet is fixed... the population is growing"

Chris Savage
08-09-2005, 05:53 AM
Danny,

· The Mill Tach project belongs to Ken Gracey and can be found here:

http://www.parallax.com/html_pages/robotics/machining/RPM_display.asp

·· As for using an optical encoder, you could do that...The QTI Sensor needs to be fairly close to the surface, is that possible in your application?· As for being too slow, that depends on how many balck/white patterns there are per revolution.· Ideally for this you will only want one change to occur.· i.e. a half black half white wheel.


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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)


Post Edited (Chris Savage (Parallax)) : 8/8/2005 10:57:49 PM GMT

Danny
08-09-2005, 05:58 AM
Yep! thats the one! Sorry Ken, Chris, I wasn't sure which one of you had it and I finally found the link on the parallax site.
I can place the sensor almost in direct contact with the wheel, so if I have a twelve slot wheel (six black/white alternating fields) moving at 3,000 rpm (almost) a fraction of an ich from the QTI line sensor it should work?

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"Never create anything you can't control"
"The amount of intelligence on the planet is fixed... the population is growing"

Danny
08-09-2005, 06:02 AM
Why is it that when I read your post the SECOND time I catch the comment about one change per revolution. Must be getting old.
I can do that too, so to revise, if I have a whell moving a almost 3000 rpm having one pulse per rev the QTI sensor will see it?

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"Never create anything you can't control"
"The amount of intelligence on the planet is fixed... the population is growing"

Danny
08-09-2005, 06:03 AM
Can't type anymore either! Need to quit thinking about new toys to build while replying to help from others.

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"Never create anything you can't control"
"The amount of intelligence on the planet is fixed... the population is growing"

Ken Gracey
08-09-2005, 06:14 AM
Danny,

We've used the·QRD-114 sensor on the back of an R/C airplane's spinner. This is the sensor which we used to have on the Boe-Bot Line Follower. Half was painted black and the other half was aluminum. You can find the video of this project at http://www.parallax.com/html_pages/resources/videolibrary/resources_product_videos.asp

The 0.46 engines spin at nearly 12K RPM if memory serves correct. So, I think it could do the job on a milling machine. But don't overlook the hall effect sensors as a good solution. With oil and coolant all over the place it could also be a good solution.

Ken Gracey
Parallax, Inc.

Danny
08-09-2005, 06:49 AM
Thanks Ken! Thats what I was looking for, I'm not worried about coolant and and oil, I'm mostly planning to "modify" existing aluminum parts and work with plastic for prototyping. I did a lot of looking before settling on the Sherline, also looked at your machine, the Sherline 5400 fits both my workspace and workload better than your mill. But I wish I could justify the investment in a Wabeco mill! Maybe if one of my "crazy" idea takes off, I can upgrade my workspace and tools! But as long as I am inventing in my spare time my budget and space is limited by my boss (wife).
Thanx again!
Danny

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"Never create anything you can't control"
"The amount of intelligence on the planet is fixed... the population is growing"

Ken Gracey
08-09-2005, 07:03 AM
Danny,

You made the right decision to go with Sherline. I view them to be the "Parallax equivalent" in small milling machines. Good stuff, lots of add-on tools, accessories, fair prices and reliable supply.

- Ken