DRO using Chinese (caliper) scales

Richard S.

I have developed a counter routine for "Chinese caliper scales" frequently used for hobbyist DRO on desktop mills + lathes.· The program is·about 85%·finished.· It will read the scales but software and hardware have not yet been developed to set scale parameters.· It has been tested with one scale and works well.· ·I have linked the scale reading object (cs_caliper)·into a previous program developed to read quadrature encoders since there are alot of similarities, but some of the quad dro stuff needs to be changed or gutted....the merge is not complete.·

I am releasing this for·general use...please ignore the copyright statement.· I have not had time to work further on either project.· The input lines from the scale need to be buffered and·brought up to proper voltage....I used a transistor to pull each data line to 5 volts, then used 74c14 schmidt trigger to clean up the data and then ran the data (with a voltage dropping resistor) into the propeller input pins.· The hardware that remains to be·developed is to·use several output pins from the propeller to pull a couple of pins on the scale to zero or 1.1 volts (logic 0 or logic 1).· The circuit with the most promise is the one by ShumaTech DRO, using a 74hc4316, a quad analog switch. a clever design!

Here is a link to my quadrature encoder DRO discussion...· ·http://forums.parallax.com/showthread.php?p=720621

The archive of the Chinese/caliper scale DRO program is attached.

This·note is for CRMWASH who requested the·CS file.· Let me know if this helpful.·

Regards

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Richard in Michigan

Richard S.

Ooops....scale voltages should be logic 0 = 0v, logic 1 = 1.5v.

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Richard in Michigan

CMRWASH

Thank you Richard, This is my first propeller project, it will help allot. I will update you on how it goes.