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Quick and simple tach project

When I bought my mini lathe, one of the first things I noticed is that there is a port on the control panel for a tachometer.  Unfortunately, the official tach costs about $127 and looks like this.  I decided that since the port was already there and the tach just plugged right in, the signal must already be hot on the port and I just needed to make something to read it.  As I was busting out my logic analyzers and oscilloscopes and other various fun electronics tools, I decided to do a few Google searches since someone had to have already worked this out.  After a few hours of searching (this was way harder than I thought it would be), I hit pay dirt.  Jeffrey Nelson of macpod.net had already done exactly this for his Sieg Mini Mill.  He saved me days of headaches and frustration.

It ends up being a very simple project.  All you need is a 16×2 LCD available from a slew of electronics shops online, an Arduino microcontroller (retail or self-built), a project enclosure, some perf board, a 7-pin female mic connector and some bits of wire and various electronics components.  I started by building the circuit on a breadboard to test it all out but unfortunately, I forgot to take pictures of this process.  Once I got it working on the breadboard, it was a simple matter to transfer everything to the perf board.  I don’t think a retail Arduino would have fit in the enclosure I bought so I’m glad I had some spare ATMega328 chips with the Arduino bootloader on them laying around.  I like to lay out my components first to figure out where everything will fit, solder those in and then start wiring it up.  I don’t really plan on servicing or upgrading this unit so I didn’t really worry about keeping it clean and just ran the wires wherever they would fit.  All in all, it was a total of about 8 hours of time spread out over a week and it works perfectly.  After I got it running I realized that I forgot to change the Arduino code to fix the spelling error and remove the website advertisement.  I added a 6-pin header to plug a 3.3V FTDI Basic chip for programming the Arduino but it’s a pain to get to.  I should have mounted it to the side of the enclosure for easy access instead of soldering it to the perf board.  Oh well.  I took some pictures of the perf board buildup and the finished project, enjoy.

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