Shumatech DRO350

Created by: Administrator, Last modification: Sun 20 of Dec, 2009 (22:10 UTC) by Lester Caine
DRO350 Digital Readiout
Shumatech DRO350 Prices

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, software, and PCB files (Gerbers) freely available for download at the Shumatech site. 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. The following list highlights the features designed into the DRO-350.

The following list highlights the features designed into the DRO-350.



  • 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

Having assembled a unit using the UK parts list, I now know how I want to proceed, but this is a matter of choice. The translation of the USA Parts List is available ( {file id=718 output=desc download}, {file id=719 output=desc download} ), and I can now supply a complete set of parts for building the board.

I modified the build instructions slightly, first assembling the PIC programmer and PIC circuitry, including it's programming header, so that I could program it before proceeding further. The only problem I found here was that a fast computer had trouble using the software successfully, while a nice slow K6 machine with W98SE had no problems. Once I had a programmed device, I started adding the power supply circuitry, and the top section of the display. This powered up and displayed the title without any problem, and progressed to the second line, which was also tested before proceeding to the third line. The only problem I had was that once the buttons were added, a solder splash ment that once section of buttons did not operate. This was fairly easy to spot, but requires care with the close proximity of via holes to soldered pads. Once all this was working, the two scales I currently have are working fine.

European Construction Guide

Since the supply of electronic products in Europe is strictly controlled, the only way to provide assembled boards commercially, is to provide a full EMC and LV directive testing on the unit. Which would be prohibitive on it's cost. When time permits, I will run up my own EMC tests, and check for problems, but the lack of a ground plane on the PCB which is running with 20MHz signals may require a fully screened metal box to meet radiated emission requirements. I am happy to complete boards that people are having problems with as this gets round the problem of 'first provision' and is simply repairing an existing product. The cost of this service would be £30 + any replacement parts.

Shumatech Price List -- European Scales List