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Yet another caliper DRO

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gzoerner

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#1
Just finished a Harbor Freight $10 caliper DRO using an Arduino Nano for the computer horsepower. It mounts on the cross slide of my Grizzly G4000 lathe. This version has a feature that measures the Diameter of the workpiece in addition to the ordinary X-position. No more stopping to make measurements as I cut down to size (or bore up to size.)

Many thanks to the members here for inspiration and especially to Randy Jaco for his suggestion to cut slots in the hardened steel rather than drilling.

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Caliper mounted on cross slide
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close up of the mounting with the slots covered
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Front panel with 1602 display and 4x4 membrane keypad (the Arduino Nano is inside). The upper blank panel is for the next project (it still needs painting)

A .ZIP file of the whole project including the schematic and software source code is attached.

Glen
 

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tweinke

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#2
Wow nice well thought out project. Looks like a nice clean install too!
 

Bamban

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#3
Very nice, you should package and market the electronics.
 

Creativechipper

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#4
Very nice!
I cant see how it actuates the calipers and such but sounds cool.
More pics please.
 

scoopydo

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#5
gzoerner,

This a great project and you've made it pretty simple with everything needed in the kit zip file. I have everything in stock so I think I'm going to give it a go. One question though, are you just soldering the 4 wires on the other end rj45 to the pads in the scale? Seems to be the best way, also where do you solder the 10uf cap in there too?
 

gzoerner

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#6
Hi Scooby,

I soldered the wires to the pads on the caliper. The pads are pretty small. Fortunately I have a very tiny soldering iron with thin solder. You probably can skip the 10uF capacitor. I just soldered it into the backs of the battery connector in the battery compartment

Good luck. If you have any more questions, I'm happy to help.

Glen
 

scoopydo

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#7
Thanks, Glen.

I figured that was where the cap went. I also have a small tip for my soldering iron so it shouldn't be a problem.

George
 

scrollsawer61

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#8
That is a great installation. Tried to download your zip file, was unable to on my IPad as I would love to fit it to my Seig C6. Any chance of a PDF file of all the info Please.

Thank you
Barry,
Australia
 

gzoerner

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#9
Hi Barry,

You will need access to a PC to use the Arduino code. That's the most important part of the ZIP file. There are several file types in the ZIP that don't lend themselves to conversion to PDF.

Glen
 

thunderbear

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#10
Nice work! Thanks for putting this together. This looks like exactly what I was looking for, I've been wanting to experiment with caliper-based DROs on my cross slide vise.

The caliper you're using, is it Harbor Freight product number 63710?

Do you know the pin order on the caliper?

And one final question, do you think it would be feasible to use one Arduino to read input from multiple calipers? I saw another project that used a microcontroller for each caliper that converted the signal to I2C... but I love the simplicity of hooking the up directly to the Arduino.

Cheers from Canada!
 

gzoerner

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#11
Hi Thunderbear,

Thanks for the kind words. The part number of the caliper I used is 62569. Look for the ones that say "Pittsburgh". I buy them when they are $10 with a coupon. I don't know if their other calipers use the same bit-stream. Go to the website http://www.shumatech.com/support/chinese_scales.htm for the pin connections on the caliper. This was the primary website I used for my research. Even at that, it took a bit of experimentation to get the bit-stream properly decoded.

You surely could use one Arduino do handle multiple calipers, but my software is interrupt-based using the caliper's clock as the interrupt. Arduino Nano's are so cheap (about $4 when you buy them in lots of 3) that the extra time to hack the software probably isn't worth it. Also, you'll probably need 2 displays. My version uses both lines of the 2 line display. One Nano can support multiple displays, but again the software gets a bit (slightly) more complicated.

I'm more than happy to answer any questions you've got as you go along. I know that taking someone's software isn't easy. We each have our own ways of doing things.

Glen
 

thunderbear

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#12
Thanks Glen,

I have a digital caliper of another brand that looks identical to yours (Mastercraft from Canadian Tire). Time to do some testing!

I had a look at the code, I found it really clear and well written. I think (hope) I understand what's going on.

The nano board has hardware support for two external interrupts and there are libraries to add additional interrupts that may be fast enough to read the 90kHz signal. I already have a multi-line display. Unnecessary, but would make for a fun experiment!

Torbjorn
 
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