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System overview

 

 

Scales

Linear scales attached to mini lathe and mills are attractive because they provide true reading free of backlash and they are inexpensive. There are several types of scales and calipers, the most attractive are inexpensive "chinese" scales (around $10 each) and with accuracy within 0.0005" (0.01 mm).

The description of the scales can be found at http://www.shumatech.com/support/chinese_scales.htm , in case this link is broken here is a copy of this page (all credits to www.shumatech.com).

On this page I describe how to build inexpensive system based on scales with 48-bit protocol. The major features are:

Hardware:

1. True USB output (plug-and-play, uses default HID windows driver (the same used by mouse and keyboard)).
2. Serial output (e.g. for usage with non-Windows OS).
3. Simultaneous reading of up to 3 scales.
4. Power scales from USB or 3.3V serial.
5. Automatically switch scales to fast reading mode (toggleable to fast/normal by sending "f" character (0x66) to USB or serial).
6. Automatically detects number of attached scales to reduce speed of polling.
7. Extremely inexpensive solution with minimum soldering (~$80 including 3 scales and program adapter (which is used only once)).

PC software:

1. Sizable display with automatic adjustment
2. Font and color selection
3. Precision selection
4. Inch/mm selection
5. Order of display, including turning off of any output
6. Toggle fast/slow mode

iTouch/iPhone software

1. Sizable display with two finger gesture
2. Zeroing with touching the label or crossing all labels with a finger
2. Font and color selection
3. Precision selection
4. Inch/mm selection
5. Order of display, including turning off of any output

What is needed:

1. Scales (I got 3 calipers with SRO (scale readout) output on ebay for $7.50 each+$19 shipping of all them). Here is the image:



2. Silicon Laboratories ToolsStick342DC board available at mouser.com or digikey.com for $10.5.
3. Silicon Laboratories BaseAdapter available at mouser.com or digikey.com for $18 (this adapter is needed to upload firmware to ToolsStick342 board microcontroller, its not a part of the system)
4. Free software from Silicon Laboratories (Silicon Laboratories IDE) to upload my code to the board. Alternatively Keil uVison with Silabs driver can be used.


4. 2 LED (green or red) for each scale
5 3 silicon diodes
6. Connectors, wires etc.
7. Free firmware and software available at this site