A Simplified Electronic Edge Finder

[rgsparber]

While I documented my last Electronic Edge Finder (EEF) I was also thinking about the next version. This new iteration trades less sensitivity for fewer parts and gains an automatic defense against probe crashes. It is compatible with CNC systems and has the same mechanical accuracy as the rest of my EEFs.

Using six resistors, one capacitor, two transistors, an LED, and a dual comparator, this EEF detects touchdown when the spindle resistance is greater than 1 ohm.

If you are interested, please, click here.

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

Thanks,

Rick

[DIYer]

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

Electronic Edge Finder by rgsparber

tags: electronics, edge finder

[rgsparber]

You may notice that I have simplified this circuit a bit more. The transistors are gone along with one resistor.

Rick

[Paul Alciatore]

Hi Rick,

You may remember me, Paul Alciatore; we corresponded about an earlier version edge finder you were developing. I do like and support your effort in this arena. Edge finding is an area that definitely can be improved. I am surprised that none of your versions has been picked up by a manufacturer.

I am looking at your web document in the above link and am a bit confused. The schematic, which is shown multiple times in that document, perhaps to make reading it easier, shows four wires that are connected to the spindle, the body of the machine, and perhaps to the part itself. But it is not clear which wire is connected where.

I am guessing that the two connections labeled "to machine body" are connected at the vicinity of the part (on the table or in a vise). But how? Are they just connected together at that connection point and then that connection is made to the part or the table/vise. Or perhaps one goes to the part and the other to the table/vise so Rpart is seen between them. This is not clear.

Then the spindle connection is equally unclear. Again there are two wires. But no clarification as to how they are connected to the spindle, to the body of the machine near the spindle or to the probe itself.

Perhaps the analysis makes this clear, but I haven't gone through it yet.

[rgsparber]

Hi Rick,

You may remember me, Paul Alciatore; we corresponded about an earlier version edge finder you were developing. I do like and support your effort in this arena. Edge finding is an area that definitely can be improved. I am surprised that none of your versions has been picked up by a manufacturer.

I am looking at your web document in the above link and am a bit confused. The schematic, which is shown multiple times in that document, perhaps to make reading it easier, shows four wires that are connected to the spindle, the body of the machine, and perhaps to the part itself. But it is not clear which wire is connected where.

I am guessing that the two connections labeled "to machine body" are connected at the vicinity of the part (on the table or in a vise). But how? Are they just connected together at that connection point and then that connection is made to the part or the table/vise. Or perhaps one goes to the part and the other to the table/vise so Rpart is seen between them. This is not clear.

Then the spindle connection is equally unclear. Again there are two wires. But no clarification as to how they are connected to the spindle, to the body of the machine near the spindle or to the probe itself.

Perhaps the analysis makes this clear, but I haven't gone through it yet.

Hi Paul. Of course, I remember you. The two wires labeled "to spindle" connect to the spindle via a magnet. The two wires marked "to machine body" connect to separate places inside the metal enclosure. When this enclosure rests on the mill's table, it forms a low resistance connection.

I've updated the article to hopefully reduce your confusion. Please let me know if this helps or hurts.

Rick