Universal Low Cost Electronic Edge Finder for use in a Machine Shop

I have been trying to design the ultimate Electronic Edge Finder (EEF) for over 4 years. It had to be low cost, work over a wide range of spindle bearing electrical resistances, and be 100% reliable. Well, maybe this time I have it.

This EEF is built on a Harbor Freight Multimeter which commonly goes for $6 if it is not being given away for free. The added circuit should cost under $5. It can detect changes in resistance as low as 0.1 milliohms but typically only needs to detect changes of tens of milliohms. The user is warned if the spindle resistance is too low to detect touchdown. A twist of the spindle brings it back into range. Low battery indicators and a bad connection indicator are also included.

If you are interested, please see

http://rick.sparber.org/MCEEF.pdf


Your comments are welcome. All of us are smarter than any one of us.



Thanks,

Rick

Thanks Rick.
For the most part I claim to be electronically illiterate, but your PDF explains it well enough that I think that I might be able to construct one should the need arise.

Well done, indeed. The circuit explanation makes me think you might be an EE? I have some LM324s left over from my days of electrical experimentation and may give it a try. Thanks for posting this.

Frank,

Do let me know if you build the circuit. I can always use what you learn to improve the article.

Rick

Thanks Rick! We've added your Electronic Edge Finder to our Measuring and Marking category, as well as to your builder page: Rick Sparber's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="http://www.homemadetools.net/electronic-edge-finder"><img src="http://www.homemadetools.net/uploads/152224/electronic-edge-finder.png"/></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="http://www.homemadetools.net/electronic-edge-finder">Electronic Edge Finder</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags">tags: <a href="http://www.homemadetools.net/tag/electronics">electronics</a>, <a href="http://www.homemadetools.net/tag/edge-finder">edge finder</a></div> </div> </div> </div>

Rick,
I second Marv, and thank you for the excellent video and PDF explaining the circuits. Also, your general information about using op amps will be useful for electronics experimenters. You got to love the concise packaging of the LM324 from the early 70's and so many useful applications taught and used in EE classes. Thank you for the explanations and posting (and yet another clever use of the HF multimeter).
Regards, Paul

I have improved the circuit plus doubled the size of the article. Same URL.

The device now has automatic power control yet costs about $5 less.

Rick

Congratulations rgsparber, your Electronic Edge Finder is our Best Documented Build winner for June 2016!


More importantly, this is your third Best Documented Build win, which makes you our FIRST 3-Time Best Documented Build winner, and the first recipient of our bronze wrench-on-scroll award graphic, now visible in the awards showcase in your postbit beneath your avatar.

:bow: :thumbsup: :clapping: :bananadance: :dance: https://www.homemadetools.net/forum/...BuildIcon3.png :dance: :bananadance: :clapping: :thumbsup: :bow:

Here are all of your Best Documented Build winning tools:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="/x-y-backlash-reduction-method"><img src="/uploads/116594/x-y-backlash-reduction-method.jpeg" alt="X-Y Backlash Reduction Method" /></a> </div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="/x-y-backlash-reduction-method">X-Y Backlash Reduction Method</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags"> tags: <a href="/tag/cnc">CNC</a>, <a href="/tag/mill">mill</a> </div> </div> </div> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/rotary-table-a-axis-conversion"><img src="https://www.homemadetools.net/uploads/138590/rotary-table-a-axis-conversion.png" /></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/rotary-table-a-axis-conversion">Rotary Table A Axis Conversion</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags">tags: <a href="https://www.homemadetools.net/tag/cnc">CNC</a>, <a href="https://www.homemadetools.net/tag/conversion">conversion</a>, <a href="https://www.homemadetools.net/tag/motor">motor</a>, <a href="https://www.homemadetools.net/tag/rotary-table">rotary table</a></div> </div> </div> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/electronic-edge-finder"><img src="https://www.homemadetools.net/uploads/152224/electronic-edge-finder.png"/></a></div> </div> <div class="head pngfix"></div> <div class="left pngfix"></div> <div class="right pngfix"></div> <div class="blockover b1 pngfix"> <div class="title"> <a href="https://www.homemadetools.net/electronic-edge-finder">Electronic Edge Finder</a> <span> by <a href="/builder/Rick+Sparber">Rick Sparber</a></span> </div> <div class="tags">tags: <a href="https://www.homemadetools.net/tag/electronics">electronics</a>, <a href="https://www.homemadetools.net/tag/edge-finder">edge finder</a></div> </div> </div> </div>



Please confirm your email address via PM to me, and I'll get your $35 award sent out, via your choice of PayPal, Amazon, GiftRocket, or bitcoin.

Congrats again and nice work! :rocker: