DIY DRO Adapter for iGaging Scales

Capabilities

Recommended Operation Conditions

Absolute Maximum Ratings

Mechanical Drawings

3D Printed Enclosure Assembly

Place the board into the enclosure with components facing up and power input aligned with the corresponding opening. The fit should be pretty close, so it is best to start at an angle and push the protruding part of the USB power sockets into the opening in the enclosure as shown in the picture. Then, lower the board into its position and gently press on it until it makes solid contact with the enclosure.

Insert the clear acrylic insert into the recess as shown in the photo below and place the lid on top of it. Ensure that the PCB mounting holes are aligned with the openings in the enclosure before inserting and tightening the four screws.

Port Functions

Scale Inputs

This DRO adapter board comes with pre-installed USB Micro-B female connectors. Next to each connector, there is a set of holes for a 5-pin 0.1" header that breaks out Vcc, Ground, Clock and Data lines for the axis (pin functions are marked on the underside of the board).

Tachometer

Tachometer input is pulled up to 3V and works push-pull or open drain sensors that output 3.3V square wave.

Touch Probe

Inexpensive touch probes and tool height setters work similar to a simple electrical switch. Depending on the configuration, when the probe touches the workpiece, it either opens the circuit or closes it (normally-closed or normally-open, respectively). TouchDRO board supports (and automatically detects) both types.

The probe can be connected as follows: connect one side of the switch to Ground and the other to the probe pin. If the probe has a LED, it has to be reverse-biased (backwards), or the input won't work. To test this, connect the probe to Vcc and Ground. If the LED lights up (either when the probe is touching or not touching), reverse the leads.

Power Supply

This DRO adapter is designed to be powered by a common Micro-USB power supply such as phone charger. Alternatively, +5V and Ground pins are broken out next to the Micro-USB connector to allow the use of a panel-mounted power supply jack instead.

Battery

The optional 1-cell Lithium battery can be used to provide backup power in case the adapter's power supply is disconnected. It is designed to work with Lithium Polymer batteries that have built in over-discharge protection circuits and use 2-pin JST-PH (2.0mm pitch) connectors. The charging circuit is pre-set for 100mAh charge rate and can be used with any battery that is larger than 100 mAh. In practice, the battery capacity is constrained by the physical space available in the 3D printed enclosure, which is roughly 7mm x 30mm x 45mm.

Recommended batteries:

• Lithium Ion Polymer Battery - 3.7v 350mAh [Adafruit]
• Lithium Ion Polymer Battery Ideal For Feathers - 3.7V 400mAh [Adafruit]
• YDL 3.7V 650mAh 652540 Lipo Battery Rechargeable Lithium Polymer ion Battery Pack with JST Connector [Amazon]
• AKZYTUE 3.7V 550mAh 503041 Lipo Battery Rechargeable Lithium Polymer ion Battery Pack with JST Connector [Amazon]

Note: LiPo battery naming convention is based on their physical size. For example, a LP-503562 battery measures 5mm x 35mm x 62mm. Likewise, LP-803260 measures 8mm x 32mm x 60mm.

Status LEDs

DRO scale adapter has three LEDs:

Green

Green LED is lit when the main processor is receiving power.

Blue

Blue LED indicates the current status. The codes are as follows:

Red

Red LED indicates the status of the battery charge monitor. When the battery is not connected, the state of the LED is irrelevant. Otherwise, the red LED is lit when the battery is charging and off when the battery is charged.

Connecting the Scales

• iGaging EZ-View DRO Plus, DigiMag "Remote DRO Display" and Absolute DRO Plus scales that come with Micro-USB cables can be plugged directly into the pre-installed USB Micro-B connectors
• iGaging DigiMag "Remote DRO Display" scales (and their rebranded versions such as Shars Digital Machine Scales and AccuRemote DRO scales) with Mini-USB connectors can be connected using a straight USB Mini-to-Micro adapter
• iGaging Absolute DRO Plus can be connected using a set of USB Mini-B breakout boards
• Glass/Magnetic Scales and other 5V quadrature encoders can be connected to the board using these instructions

IMPORTANT: Always disconnect the power supply and the battery when plugging or unplugging scales to avoid ESD damage to the scales or the adapter.

Grounding

Proper grounding is vital for reliable function of iGaging DRO scales. Unreliable ground connection or ground loop can lead to such issues as drifting position or random resets. In order to avoid ground loops, there should be a single reliable connection to the machine chassis. Ideally, scale frames should be isolated from the machine. If the cables are shielded, the shields should be tied to the ground only on one side and as close to the central grounding point as possible.

The board provides a number of easily accessible grounding points. Each port has a dedicated ground pin that is tied to the common ground pour. There are two ground pins next to each Micro-USB port and finally, the mounting holes are tied to the common ground as well.