Yet another CNC Compatible Electronic Edge Finder

[rgsparber]

This design is three times more sensitive than past efforts yet costs about the same. It uses analog circuit design techniques to detect any drop in resistance of more than 0.124 ohms.

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

[tonyfoale]

Rick,

This is not a criticism because if something works, it works. However, there is an easier way for those less skilled with a soldering iron. That is by using an Arduino style micro. The Uno is only 10 bit IIRC but I think that the 3.3v versions are 12 bit as is the ESP32 which I now use. That means that you have an analogue input resolution of 3.3/4096 = 0.00081 v. Let's plan on the same 100 mA that you use, then for a change in resistance of 0.124 ohms we get a voltage change of 11 mV (for your 4 ohm limit) and 14 mV (at your 0.3 ohm limit) which is over 13 and 16 times the resolution. So a 12 bit ADC input is more than capable of detecting a 0.124 ohm change, even a 10 bit conversion would work but I'd prefer the extra safety margin of 12 bit. The code for the micro would only require a few lines.

Read value.
if detect change ->
start output pulse
fire led
wait pulse duration
end output pulse
kill led
repeat loop.

[rgsparber]

Rick,

This is not a criticism because if something works, it works. However, there is an easier way for those less skilled with a soldering iron. That is by using an Arduino style micro. The Uno is only 10 bit IIRC but I think that the 3.3v versions are 12 bit as is the ESP32 which I now use. That means that you have an analogue input resolution of 3.3/4096 = 0.00081 v. Let's plan on the same 100 mA that you use, then for a change in resistance of 0.124 ohms we get a voltage change of 11 mV (for your 4 ohm limit) and 14 mV (at your 0.3 ohm limit) which is over 13 and 16 times the resolution. So a 12 bit ADC input is more than capable of detecting a 0.124 ohm change, even a 10 bit conversion would work but I'd prefer the extra safety margin of 12 bit. The code for the micro would only require a few lines.

Read value.
if detect change ->
start output pulse
fire led
wait pulse duration
end output pulse
kill led
repeat loop.

Tony,

Great minds think alike ;-)

"Easier" depends on the reader. I have already developed an Arduino based EEF and a few readers didn't like it because they only knew how to do circuits. As you can see in my article, there is a bit more to it than a simple conversion. It was also fun because I did it with an ATTiny-85 and a much smaller test current.

Rick

[Jon]

Congratulations rgsparber - your Electronic Edge Finder is the Homemade Tool of the Week!

It has been interesting watching this project evolve over the years, and it keeps getting better.

Some more good builds from this week:

Bender by Kwandotechnic
Shooting Board by Dr.Al
Horizontal Bandsaw Stand by micksworkshop
Hand Sander by orioncons36
Post Extractor by Unisawyer
Mini Mill Stop Block by JKeetonKnives
Woodturning Tool by Make Things
Parallels by Rustinox
Toolmaker's Clamp by Improvised DIY
Disc Grinder by Mr.DK DIY
Belt Sander Contact Wheels by Mazay

rgsparber - you'll be receiving a $25 online gift card, in your choice of Amazon, PayPal, or bitcoin. Please PM me your current email address and gift card choice and I'll get it sent over right away.

This is your 9th Homemade Tool of the Week. Here are all of your Homemade Tool of the Week winning tools. Congrats again

CNC Controller by rgsparber

tags: CNC, controller

Irrigation Flow System by rgsparber

tags: farm and garden, electronics

Software Defined Edge Finder by rgsparber

tags: electronics, edge finder

Drill Press Clamp Modification by rgsparber

tags: drill press, clamp

Flight Data Recorder by rgsparber

tags: electronics

Radius Fixture by rgsparber

tags: radius, fixture

Hook Forming Tool by rgsparber

tags: hooks, fixture

Storage Boxes by rgsparber

tags: storage

Electronic Edge Finder by rgsparber

tags: electronics, edge finder

[rgsparber]

I have written a comparison between this Analog Electronic Edge Finder and my Software-Defined Edge Finder. The bottom line is that the SDEF costs less and is more reliable but is harder to build if you are unfamiliar with the Arduino environment.

Rick