DIY DRO Adapter Kit for Glass Scales

TouchDRO DIY DRO Adapter Kit for Glass Scales (Unassembled) supports up to four 5V quadrature scale inputs, tachometer input, and touch probe/tool setter input. It includes a bare printed circuit board, a microcontroller pre-programmed with TouchDRO firmware, and all of the components needed for building a TouchDRO adapter.

Description

DIY DRO Kit for Glass Scales
Finished TouchDRO DIY DRO Kit for Glass Scales

The DIY Digital Readout Adapter Kit for Glass/Magnetic Scales is designed from the ground up to be cost-effective, easy to build and offers excellent performance and reliability. It supports the vast majority of modern Glass and Magnetic DRO scales, as well as standard rotary encoders that output a single-ended1 5V quadrature signal. During the assembly, the inputs can be configured to work with PNP, NPN, and Push/Pull encoders for added flexibility.

The adapter uses a fast digital buffer to provide 5 Volt-tolerant input for standard single-ended Glass and Magnetic DRO scales and other quadrature encoders. In conjunction with the optimized TouchDRO quadrature firmware, it can handle a 5-micron movement speed of at least 100mm/second (4 inches/second) when a single axis is in motion or at least 50mm/second when all four axes are moving at once.

This DIY adapter can be used with Glass and Magnetic DRO scales that output a differential signal by omitting the complementary line connections, but for those scales, the pre-made TouchDRO Adapter for Glass and Magnetic scales is recommended.

Kit Contents

This kit comes with high-quality name brand components that are derated to provide ample headroom for long-term reliability and durability. This includes:

  • Gold plated printed circuit board, electrically tested and inspected to meet IPC-A-600 Class II standard
  • TI MSP430 microcontroller, preprogrammed with TouchDRO firmware
  • Tested HC-05 BlueTooth transceiver
  • Set of Texas Instruments ICs (74xx244 buffer and two LM1117 voltage regulators)
  • HIgh-quality Panasonic electrolytic capacitors
  • Name brand resistors, capacitors, and LEDs
  • D-Sub 9 connectors, pin headers, and jumper wires for connecting various scale configurations

To complete the build, you will need to provide a set of compatible Glass or Magnetic DRO scales, a suitable non-metallic enclosure and a 7.2V-9V AC/DC power adapter with a center-positive 5.5mm barrel connector.

Each circuit board is fully electrically tested by the manufacturer. Additionally, I personally program and test every microcontroller, inspect each PCB, and check the kit before shipping it out.

Specifications

Features

  • Supports four linear axis inputs, tachometer, and a touch probe or tool setter input
  • Scale inputs can be configured for use with PNP, NPN, and push/pull sensors
  • Two separate onboard linear voltage regulators provide clean power supply voltages to the 5V scale rail and 3.3V logic rail
  • Per-scale bypass capacitors filter out transient spikes on the power supply lines
Scale Inputs 4
Tachometer Input Yes
Probe/Height Setter Yes
Power Supply 7.2V DC - 9V DC
Current Draw Approx. 200 mA
Width 2.7"
Length 2.8"

Supported Scales

This TouchDRO adapter supports a wide array of Glass and Magnetic DRO scales, as well as many standard rotary encoders that output a quadrature signal with a 5V level. This includes most, if not all, brands of budget Chinese Glass and Magnetic DRO scales, as well as the vast majority of modern brand-name DRO scales.

To ensure that your particular scales are supported, please refer to their documentation to ensure that the scales use positive 5V power supply voltage and output quadrature signal with a 5V level.

For more information about Glass and Magnetic DRO scales, refer to the pages linked below:

Mechanical Drawings

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Fig 1: Mechanical Dimensions

Circuit Schematic

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Fig 2: Circuit Schematic

Kit Contents

This DIY DRO kit includes all of the components needed to assemble a TouchDRO adapter.

DIY DRO Kit for Glass Scales Parts
Value Description Qty. Reference
PCB TouchDRO Adapter PCB, Immersion Gold plated, Green solder mask, White silkscreen 1 N/A
MSP430G2553 16-Bit mixed-signal microcontroller (pre-programmed) 1 U1
74xx244 SN74HC244 Octal Buffer 1 U1
HC-05 Bluetooth Transceiver, Slave 1 HC-05
LM1117T-3.3 Voltage Regulator, 3.3V 800 mA, LDO 1 LM1117
LM1117T-5.0 Voltage Regulator, 5.0V 800 mA, LDO 1 LM1117
Capacitor, 100 uF Cap. electrolytic, 100uF, 35V 3 C1, C2, C3
Capacitor, 0.1uF Cap. ceramic, 0.1uF 50V 12 C4-C15
Resistor, 330 Ohm Metal film resistor, 330 Ohm, 1/4W, 5% 2 R2, R3
Resistor 47KOhm Metal film resistor, 47 KOhm, 1/4W, 5% 1 R1
Resistor Network Resistor Network, 47KOhm, 10 Pin 1 RN1
LED LED, Green 3mm, 20 mA 2 HB, PWR
Pin Header Pin Header, 4x1, 1" spacing 5 X,Y,Z,W, HC-05 (optional)
Scale Connector D-Sub 9 Pin, Female, Panel Mount 4 N/A
Power Jack 2.1x5.5 mm power input jack, PCB mount 1 Pwr

Documentation

Useful Resources

Port Functions

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Fig 3: Input Ports
Port Description 5V-Tolerant Note
X,Y,Z,W Inputs for four linear axes Yes Pulled up/down depending on RN1 position
Tach. Tachometer input No Pulled up to 3.3V
Probe Touch probe input No Pulled up to 3.3V
Power 7.2V-9V Power input N/A 2mm x 5.5mm barrel, center positive
PROG ESP32 Programming Port No Used to re-prgam MSP430

Note that the scale inputs on this adapter are 5-Volt tolerant since they are connected to the TTL digital buffer IC. On the other hand, the tachometer and probe inputs are not 5V-tolerant since they are connected directly to the MSP430 microcontroller and will be damaged by voltage exceeding 3.3V.

Axis Inputs

TouchDRO DIY DRO Adapter Kit for Glass Scales supports up to four quadrature axis inputs. During the assembly, the inputs can be configured to work with NPN, PNP, and Push/Pull sensors by altering the location of the pull up/down resistor array.

Tachometer

The board supports non-directional tachometer input with a frequency range of 1Hz to 10KHz. The tachometer input pin is pulled up to 3.3V via an internal resistor; the tachometer should provide a sinking (NPN/open-collector) or push/pull output.

Touch Probe

Touch probe input is a binary on/off input. The pin is pulled up to 3.3V via an internal resistor. The firmware can handle either a normally-open or normally-closed probe. During boot time, it detects the state of the input and assumes that the probe is in the "Off" state; the opposite state will be treated as "On".

Power Input

The board uses a center-positive 5.5mm x 2.1mm power input jack. The on-board voltage regulators can use supply voltage ranging from about 3.6V DC to 12V DC and can work with a range of power supplies. For best results, a power supply should provide at least 200 mA of current and 7.2V to 9V.

A 2-pin "Pwr." header is wired in parallel with the power jack. It provides an option to use a panel-mounted power jack with an inline On/Off switch.

Grounding

Proper grounding is very important for the stable operation of your DIY DRO setup. In order to reduce EMF issues, ground the board to the machine's frame and ensure that the scales' cables are connected to the ground only on one side. Mounting holes on the board are tied to the ground fill, as are all of the ground pins. For more details please refer to the "Avoiding Common DRO Scale Problems" page.