The DRO-350 is a three-axis digital read-out (DRO) for import Chinese scales and most quadrature encoders that is designed to be as capable as commercial DROs but be a low cost alternative for the metal-working hobbyist.  The DRO-350 is a do-it-yourself (DIY) project, not a complete, commercially manufactured product.  All of the components necessary to build it are commonly available at Digikey, Mouser, or other electronics distributors.  The printed circuit board (PCB) is specifically designed to use only DIP devices to make it easier for a hobbyist to assemble.  The custom components needed to build the DRO-350, the bare PCB and the silk-screened overlay, are available to order on this site.  The construction process is shown in step-by-step detail on the construction page and it is easy enough for somebody with basic electronics experience to build.  If you don't feel comfortable building one yourself, you can send an e-mail to the ShumaTech Yahoo! group to see if someone is willing to build one for you.

The DRO-350 is an open project with the schematics and software freely available for download at this site.  The DRO-350 is NOT a public domain project.  I retain all rights for works presented here and will grant a license to use said works in any way you should see fit provided that it is for non-commercial use only.  You are free to build DRO-350's for yourself but I will not allow any kind of commercial use of the works presented here without prior arrangements.  OK, enough of the legal statements and let's get on with the fun stuff...

One of the more exciting aspects of the DRO-350 is that the firmware is easily upgradeable over a serial port.  This allows for continued development of the software and should allow the DRO-350 project to grow over time.  Software is available for both Windows and Linux and you need only a 9 pin serial cable to connect the DRO-350.  More information on the firmware upgrade capability can be found on the software page.  The following list highlights the features designed into the DRO-350.

Features

• Software upgradeable over RS-232 serial port with free Windows software
• Fast scale reading with a display update rate of up to 50 times a second per axis
• Powers scales for battery-free operation
• Triple data sampling for glitch free readings
• Three axis display with super high efficiency LEDS for maximum brightness
• Display brightness configurable in 20% increments
• Max display range of ±99.9995 inches (±999.99 mm)
• Incremental and absolute coordinate systems
• Enter zero values for both coordinate systems entered via keypad
• Enter incremental presets via keypad
• Separate zero and preset buttons for each axis
• Data averaging when the scale is at rest to prevent display jitter
• Auxiliary input for either an electronic edge finder or tachometer
• Third axis configurable to display tachometer in RPM or SFM
• Reversible axis directions
• Configurable auto power-off time (none, 15 min, 30 min, 60 min)
• Configurable tool offsets entered via keypad
• Setup through display and keypad
• Setup is retained even if power is removed
• Absolute zeroes and inch/metric setting are retained even after a power loss
• Configurable CPI for use with quadrature encoders (10-25000 CPI)
  
• Polarity axis setting to alter the location of the origin

Mill-Only Features

• Centerline function for any axis
• Bolt hole patterns with programmable start and end angles
• Cutting edge compensation based on tool offsets

Lathe-Only Features

• Diameter mode (2X) for any axis with a LED indicator displayed in each axis
• Compound vectoring into cross-slide and carriage with configurable angle

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