Electronic Edge Finder

I use this mostly on my mill. It was cheaper to make than buy.
https://www.youtube.com/watch?v=8PRueKjn_Iw

An LED driven by a 12-volt battery definitely requires a resistor if you want it to last. Most 5mm LEDs are quite happy running at 20 mA. A typical 5mm white LED has a voltage drop of 3.6 volts at 20mA, which indicates a resistor of 420 ohms. 430 ohms is a standard value. 470 would work fine too. Other colors have different voltages but 470 ohms would work OK with any of them.
A good source for LEDs is
https://www.ledsupply.com/5mm-leds
Good selection, reasonable small-quantity pricing, free first-class shipping.

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Thanks mr_modify1! We've added your Electronic Edge Finder to our Electronics category,
as well as to your builder page: mr_modify1's Homemade Tools. Your receipt:

<div id="blocks"> <div class="block b1 pngfix"> <div class="bimg"> <div> <a href="https://www.homemadetools.net/homemade-electronic-edge-finder-2"> <img src="/uploads/252486/homemade-electronic-edge-finder-2.jpeg"/> </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/homemade-electronic-edge-finder-2">Electronic Edge Finder</a> <span> by <a href="https://www.homemadetools.net/builder/mr_modify1">mr_modify1</a></span> </div> <div class="tags">tags: <a href='https://www.homemadetools.net/tag/led'>LED</a>, <a href='https://www.homemadetools.net/tag/edge-finder'>edge finder</a> </div> </div> </div> </div>
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Thanks for the info. I know enough about electronics just to get in trouble.